Release version 6.1 RC1 (2026.0.0).

See #3258

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ name: CI Build
 on:
   workflow_dispatch:
   push:
-    branches: [ 5.5.x, 'issue/5.5.x/**' ]
+    branches: [ main, 'issue/**' ]
 
 permissions: read-all
 
@@ -11,17 +11,17 @@ jobs:
   build-java:
     strategy:
       matrix:
-        java-version: [ base, next ]
+        java-version: [ base, main ]
     name: Build project
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
       - name: Setup Java and Maven
-        uses: spring-projects/spring-data-build/actions/setup-maven@3.5.x
+        uses: spring-projects/spring-data-build/actions/setup-maven@main
         with:
           java-version: ${{ matrix.java-version }}
           develocity-access-key: '${{ secrets.DEVELOCITY_ACCESS_KEY }}'
       - name: Build
-        uses: spring-projects/spring-data-build/actions/maven-build@3.5.x
+        uses: spring-projects/spring-data-build/actions/maven-build@main
         env:
           TESTCONTAINERS_REUSE_ENABLE: true

.github/workflows/project.yml

@@ -1,45 +0,0 @@
-# GitHub Actions to automate GitHub issues for Spring Data Project Management
-
-name: Spring Data GitHub Issues
-
-on:
-  issues:
-    types: [opened, edited, reopened]
-  issue_comment:
-    types: [created]
-  pull_request_target:
-    types: [opened, edited, reopened]
-
-permissions:
-  contents: read
-  issues: write
-  pull-requests: write
-
-jobs:
-  Inbox:
-    runs-on: ubuntu-latest
-    if: github.repository_owner == 'spring-projects' && (github.event.action == 'opened' || github.event.action == 'reopened') && github.event.pull_request == null && !contains(join(github.event.issue.labels.*.name, ', '), 'dependency-upgrade') && !contains(github.event.issue.title, 'Release ')
-    steps:
-      - name: Create or Update Issue Card
-        uses: actions/add-to-project@v1.0.2
-        with:
-          project-url: https://github.com/orgs/spring-projects/projects/25
-          github-token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}
-  Pull-Request:
-    runs-on: ubuntu-latest
-    if: github.repository_owner == 'spring-projects' && (github.event.action == 'opened' || github.event.action == 'reopened') && github.event.pull_request != null
-    steps:
-      - name: Create or Update Pull Request Card
-        uses: actions/add-to-project@v1.0.2
-        with:
-          project-url: https://github.com/orgs/spring-projects/projects/25
-          github-token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}
-  Feedback-Provided:
-    runs-on: ubuntu-latest
-    if: github.repository_owner == 'spring-projects' && github.event_name == 'issue_comment' && github.event.action == 'created' && github.actor != 'spring-projects-issues' && github.event.pull_request == null && github.event.issue.state == 'open' && contains(toJSON(github.event.issue.labels), 'waiting-for-feedback')
-    steps:
-      - name: Update Project Card
-        uses: actions/add-to-project@v1.0.2
-        with:
-          project-url: https://github.com/orgs/spring-projects/projects/25
-          github-token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}

.github/workflows/snapshots.yml

@@ -3,7 +3,7 @@ name: Snapshots
 on:
   workflow_dispatch:
   push:
-    branches: [ 5.5.x, 'issue/5.5.x/**' ]
+    branches: [ main, 'issue/**' ]
 
 permissions: read-all
 
@@ -15,11 +15,11 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - name: Setup Java and Maven
-        uses: spring-projects/spring-data-build/actions/setup-maven@3.5.x
+        uses: spring-projects/spring-data-build/actions/setup-maven@main
         with:
           develocity-access-key: '${{ secrets.DEVELOCITY_ACCESS_KEY }}'
       - name: Deploy to Artifactory
-        uses: spring-projects/spring-data-build/actions/maven-artifactory-deploy@3.5.x
+        uses: spring-projects/spring-data-build/actions/maven-artifactory-deploy@main
         env:
           TESTCONTAINERS_REUSE_ENABLE: true
         with:

.mvn/wrapper/maven-wrapper.properties

@@ -1,3 +1,3 @@
-#Thu Jul 17 14:00:55 CEST 2025
+#Thu Jul 17 13:59:56 CEST 2025
 wrapperUrl=https\://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar
 distributionUrl=https\://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.11/apache-maven-3.9.11-bin.zip

pom.xml

@@ -5,12 +5,12 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-elasticsearch</artifactId>
-	<version>5.5.10</version>
+	<version>6.1.0-RC1</version>
 
 	<parent>
 		<groupId>org.springframework.data.build</groupId>
 		<artifactId>spring-data-parent</artifactId>
-		<version>3.5.10</version>
+		<version>4.1.0-RC1</version>
 	</parent>
 
 	<name>Spring Data Elasticsearch</name>
@@ -18,16 +18,16 @@
 	<url>https://github.com/spring-projects/spring-data-elasticsearch</url>
 
 	<properties>
-		<springdata.commons>3.5.10</springdata.commons>
+		<springdata.commons>4.1.0-RC1</springdata.commons>
 
 		<!-- version of the ElasticsearchClient	-->
-		<elasticsearch-java>8.18.8</elasticsearch-java>
+		<elasticsearch-java>9.3.4</elasticsearch-java>
+		<elasticsearch-rest-client>9.3.3</elasticsearch-rest-client>
 
-		<hoverfly>0.19.0</hoverfly>
-		<log4j>2.23.1</log4j>
+		<hoverfly>0.20.2</hoverfly>
+		<log4j>2.25.4</log4j>
 		<jsonassert>1.5.3</jsonassert>
-		<testcontainers>1.20.0</testcontainers>
-		<wiremock>3.9.1</wiremock>
+		<wiremock>3.9.2</wiremock>
 
 		<java-module-name>spring.data.elasticsearch</java-module-name>
 
@@ -91,6 +91,27 @@
 		<url>https://github.com/spring-projects/spring-data-elasticsearch/issues</url>
 	</issueManagement>
 
+
+	<dependencyManagement>
+		<dependencies>
+
+			<dependency>
+				<groupId>org.apache.commons</groupId>
+				<artifactId>commons-lang3</artifactId>
+				<version>3.19.0</version>
+				<scope>test</scope>
+			</dependency>
+
+			<dependency>
+				<groupId>commons-io</groupId>
+				<artifactId>commons-io</artifactId>
+				<version>2.20.0</version>
+				<scope>test</scope>
+			</dependency>
+
+		</dependencies>
+	</dependencyManagement>
+
 	<dependencies>
 
 		<!-- Spring -->
@@ -136,30 +157,52 @@
 			</exclusions>
 		</dependency>
 
+		<!-- the old RestCLient is an optional dependency for user that still want to use it-->
 		<dependency>
 			<groupId>org.elasticsearch.client</groupId>
 			<artifactId>elasticsearch-rest-client</artifactId>
-			<version>${elasticsearch-java}</version>
+			<version>${elasticsearch-rest-client}</version>
 			<exclusions>
 				<exclusion>
 					<groupId>commons-logging</groupId>
 					<artifactId>commons-logging</artifactId>
 				</exclusion>
 			</exclusions>
+			<optional>true</optional>
+		</dependency>
+
+		<dependency>
+			<groupId>com.querydsl</groupId>
+			<artifactId>querydsl-core</artifactId>
+			<version>${querydsl}</version>
+			<optional>true</optional>
 		</dependency>
 
 		<!-- Jackson JSON Mapper -->
+		<dependency>
+			<groupId>tools.jackson.core</groupId>
+			<artifactId>jackson-core</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>tools.jackson.core</groupId>
+			<artifactId>jackson-databind</artifactId>
+		</dependency>
+
+        <!-- Version 2 to use with the legacy RestClient -->
 		<dependency>
 			<groupId>com.fasterxml.jackson.core</groupId>
 			<artifactId>jackson-core</artifactId>
+            <scope>provided</scope>
+            <optional>true</optional>
 		</dependency>
 		<dependency>
 			<groupId>com.fasterxml.jackson.core</groupId>
 			<artifactId>jackson-databind</artifactId>
+            <scope>provided</scope>
+            <optional>true</optional>
 		</dependency>
 
 		<!-- CDI -->
-
 		<dependency>
 			<groupId>javax.interceptor</groupId>
 			<artifactId>javax.interceptor-api</artifactId>
@@ -233,6 +276,14 @@
 			<optional>true</optional>
 		</dependency>
 
+		<dependency>
+			<groupId>org.jetbrains</groupId>
+			<artifactId>annotations</artifactId>
+			<version>26.0.2-1</version>
+			<scope>test</scope>
+			<optional>true</optional>
+		</dependency>
+
 		<dependency>
 			<groupId>org.slf4j</groupId>
 			<artifactId>log4j-over-slf4j</artifactId>
@@ -284,21 +335,6 @@
 			<scope>test</scope>
 		</dependency>
 
-		<!-- Upgrade xbean to 4.5 to prevent incompatibilities due to ASM versions -->
-		<dependency>
-			<groupId>org.apache.xbean</groupId>
-			<artifactId>xbean-asm5-shaded</artifactId>
-			<version>4.5</version>
-			<scope>test</scope>
-		</dependency>
-
-		<dependency>
-			<groupId>javax.servlet</groupId>
-			<artifactId>javax.servlet-api</artifactId>
-			<version>3.1.0</version>
-			<scope>test</scope>
-		</dependency>
-
 		<dependency>
 			<groupId>org.mockito</groupId>
 			<artifactId>mockito-junit-jupiter</artifactId>
@@ -308,16 +344,7 @@
 
 		<dependency>
 			<groupId>org.testcontainers</groupId>
-			<artifactId>elasticsearch</artifactId>
-			<version>${testcontainers}</version>
-			<scope>test</scope>
-		</dependency>
-
-		<!--we need Murmur3Hash in a test, before 5.2 we had it from the old Elasticsearch dependency	-->
-		<dependency>
-			<groupId>commons-codec</groupId>
-			<artifactId>commons-codec</artifactId>
-			<version>1.15</version>
+			<artifactId>testcontainers-elasticsearch</artifactId>
 			<scope>test</scope>
 		</dependency>
 
@@ -328,7 +355,13 @@
 			<scope>test</scope>
 		</dependency>
 
-	</dependencies>
+        <dependency>
+            <groupId>io.micrometer</groupId>
+            <artifactId>micrometer-observation-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
 
 	<build>
 		<resources>

src/main/antora/antora-playbook.yml

@@ -17,7 +17,7 @@ content:
     - url: https://github.com/spring-projects/spring-data-commons
       # Refname matching:
       # https://docs.antora.org/antora/latest/playbook/content-refname-matching/
-      branches: [ main, 3.4.x, 3.3.x ]
+      branches: [ main ]
       start_path: src/main/antora
 asciidoc:
   attributes:

src/main/antora/modules/ROOT/nav.adoc

@@ -12,6 +12,7 @@
 *** xref:migration-guides/migration-guide-5.2-5.3.adoc[]
 *** xref:migration-guides/migration-guide-5.3-5.4.adoc[]
 *** xref:migration-guides/migration-guide-5.4-5.5.adoc[]
+*** xref:migration-guides/migration-guide-5.5-6.0.adoc[]
 
 
 * xref:elasticsearch.adoc[]

src/main/antora/modules/ROOT/pages/elasticsearch.adoc

@@ -5,7 +5,7 @@
 Spring Data support for Elasticsearch contains a wide range of features:
 
 * Spring configuration support for various xref:elasticsearch/clients.adoc[Elasticsearch clients].
-* The xref:elasticsearch/template.adoc[`ElasticsearchTemplate` and `ReactiveElasticsearchTemplate`] helper classes that provide object mapping between ES index operations and POJOs.
+* The xref:elasticsearch/template.adoc[`ElasticsearchTemplate` and `ReactiveElasticsearchTemplate`] helper classes that provide object mapping between Elasticsearch index operations and POJOs.
 * xref:elasticsearch/template.adoc#exception-translation[Exception translation] into Spring's portable {springDocsUrl}data-access.html#dao-exceptions[Data Access Exception Hierarchy].
 * Feature rich xref:elasticsearch/object-mapping.adoc[object mapping] integrated with _Spring's_ {springDocsUrl}core.html#core-convert[Conversion Service].
 * xref:elasticsearch/object-mapping.adoc#elasticsearch.mapping.meta-model.annotations[Annotation-based mapping] metadata that is extensible to support other metadata formats.

src/main/antora/modules/ROOT/pages/elasticsearch/auditing.adoc

@@ -10,7 +10,7 @@ In order for the auditing code to be able to decide whether an entity instance i
 ----
 package org.springframework.data.domain;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 public interface Persistable<ID> {
     @Nullable
@@ -81,5 +81,5 @@ class MyConfiguration {
 }
 ----
 
-If your code contains more than one `AuditorAware` bean for different types, you must provide the name of the bean to use as an argument to the `auditorAwareRef` parameter of the 
- `@EnableElasticsearchAuditing` annotation. 
+If your code contains more than one `AuditorAware` bean for different types, you must provide the name of the bean to use as an argument to the `auditorAwareRef` parameter of the
+ `@EnableElasticsearchAuditing` annotation.

src/main/antora/modules/ROOT/pages/elasticsearch/clients.adoc

@@ -6,10 +6,10 @@ This chapter illustrates configuration and usage of supported Elasticsearch clie
 Spring Data Elasticsearch operates upon an Elasticsearch client (provided by Elasticsearch client libraries) that is connected to a single Elasticsearch node or a cluster.
 Although the Elasticsearch Client can be used directly to work with the cluster, applications using Spring Data Elasticsearch normally use the higher level abstractions of xref:elasticsearch/template.adoc[Elasticsearch Operations] and xref:elasticsearch/repositories/elasticsearch-repositories.adoc[Elasticsearch Repositories].
 
-[[elasticsearch.clients.restclient]]
-== Imperative Rest Client
+[[elasticsearch.clients.rest5client]]
+== Imperative Rest5Client
 
-To use the imperative (non-reactive) client, a configuration bean must be configured like this:
+To use the imperative (non-reactive) Rest5Client - the default client provided by the Elasticsearch Java client library from version 9 on -, a configuration bean must be configured like this:
 
 ====
 [source,java]
@@ -31,7 +31,7 @@ public class MyClientConfig extends ElasticsearchConfiguration {
 <.> for a detailed description of the builder methods see xref:elasticsearch/clients.adoc#elasticsearch.clients.configuration[Client Configuration]
 ====
 
-The javadoc:org.springframework.data.elasticsearch.client.elc.ElasticsearchConfiguration[]] class allows further configuration by overriding for example the `jsonpMapper()` or `transportOptions()` methods.
+The javadoc:org.springframework.data.elasticsearch.client.elc.ElasticsearchConfiguration[] class allows further configuration by overriding for example the `jsonpMapper()` or `transportOptions()` methods.
 
 
 The following beans can then be injected in other Spring components:
@@ -39,7 +39,85 @@ The following beans can then be injected in other Spring components:
 ====
 [source,java]
 ----
-import org.springframework.beans.factory.annotation.Autowired;@Autowired
+import org.springframework.beans.factory.annotation.Autowired;
+
+@Autowired
+ElasticsearchOperations operations;      <.>
+
+@Autowired
+ElasticsearchClient elasticsearchClient; <.>
+
+@Autowired
+Rest5Client rest5Client;                 <.>
+
+@Autowired
+JsonpMapper jsonpMapper;                 <.>
+----
+
+<.> an implementation of javadoc:org.springframework.data.elasticsearch.core.ElasticsearchOperations[]
+<.> the `co.elastic.clients.elasticsearch.ElasticsearchClient` that is used.
+<.> the low level `Rest5Client` from the Elasticsearch libraries
+<.> the `JsonpMapper` user by the Elasticsearch `Transport`
+====
+
+Basically one should just use the javadoc:org.springframework.data.elasticsearch.core.ElasticsearchOperations[] to interact with the Elasticsearch cluster.
+When using repositories, this instance is used under the hood as well.
+
+[[elasticsearch.clients.restclient]]
+== Deprecated Imperative RestClient
+
+To use the imperative (non-reactive) RestClient - deprecated since version 6 - , the following dependency needs to be added, adapt the correct version. The exclusion is needed in a Spring Boot application:
+====
+[source,xml]
+----
+        <dependency>
+            <groupId>org.elasticsearch.client</groupId>
+            <artifactId>elasticsearch-rest-client</artifactId>
+            <version>${elasticsearch-client.version}</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>commons-logging</groupId>
+                    <artifactId>commons-logging</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+
+----
+====
+
+The configuration bean must then be configured like this:
+
+====
+[source,java]
+----
+import org.springframework.data.elasticsearch.client.elc.ElasticsearchLegacyRestClientConfiguration;
+
+@Configuration
+public class MyClientConfig extends ElasticsearchLegacyRestClientConfiguration {
+
+	@Override
+	public ClientConfiguration clientConfiguration() {
+		return ClientConfiguration.builder()           <.>
+			.connectedTo("localhost:9200")
+			.build();
+	}
+}
+----
+
+<.> for a detailed description of the builder methods see xref:elasticsearch/clients.adoc#elasticsearch.clients.configuration[Client Configuration]
+====
+
+The javadoc:org.springframework.data.elasticsearch.client.elc.ElasticsearchConfiguration[] class allows further configuration by overriding for example the `jsonpMapper()` or `transportOptions()` methods.
+
+
+The following beans can then be injected in other Spring components:
+
+====
+[source,java]
+----
+import org.springframework.beans.factory.annotation.Autowired;
+
+@Autowired
 ElasticsearchOperations operations;      <.>
 
 @Autowired
@@ -61,8 +139,8 @@ JsonpMapper jsonpMapper;                 <.>
 Basically one should just use the javadoc:org.springframework.data.elasticsearch.core.ElasticsearchOperations[] to interact with the Elasticsearch cluster.
 When using repositories, this instance is used under the hood as well.
 
-[[elasticsearch.clients.reactiverestclient]]
-== Reactive Rest Client
+[[elasticsearch.clients.reactiverest5client]]
+== Reactive Rest5Client
 
 When working with the reactive stack, the configuration must be derived from a different class:
 
@@ -93,6 +171,69 @@ The following beans can then be injected in other Spring components:
 ====
 [source,java]
 ----
+import org.springframework.beans.factory.annotation.Autowired;
+
+@Autowired
+ReactiveElasticsearchOperations operations;      <.>
+
+@Autowired
+ReactiveElasticsearchClient elasticsearchClient; <.>
+
+@Autowired
+Rest5Client rest5Client;                           <.>
+
+@Autowired
+JsonpMapper jsonpMapper;                         <.>
+----
+
+the following can be injected:
+
+<.> an implementation of javadoc:org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations[]
+<.> the `org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchClient` that is used.
+This is a reactive implementation based on the Elasticsearch client implementation.
+<.> the low level `RestClient` from the Elasticsearch libraries
+<.> the `JsonpMapper` user by the Elasticsearch `Transport`
+====
+
+Basically one should just use the javadoc:org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations[] to interact with the Elasticsearch cluster.
+When using repositories, this instance is used under the hood as well.
+
+[[elasticsearch.clients.reactiverestclient]]
+== Deprecated Reactive RestClient
+
+See the section above for the imperative code to use the deprecated RestClient for the necessary dependencies to include.
+
+When working with the reactive stack, the configuration must be derived from a different class:
+
+====
+[source,java]
+----
+import org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchLegacyRestClientConfiguration;
+
+@Configuration
+public class MyClientConfig extends ReactiveElasticsearchLegacyRestClientConfiguration {
+
+	@Override
+	public ClientConfiguration clientConfiguration() {
+		return ClientConfiguration.builder()           <.>
+			.connectedTo("localhost:9200")
+			.build();
+	}
+}
+----
+
+<.> for a detailed description of the builder methods see xref:elasticsearch/clients.adoc#elasticsearch.clients.configuration[Client Configuration]
+====
+
+The javadoc:org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchConfiguration[] class allows further configuration by overriding for example the `jsonpMapper()` or `transportOptions()` methods.
+
+The following beans can then be injected in other Spring components:
+
+====
+[source,java]
+----
+import org.springframework.beans.factory.annotation.Autowired;
+
 @Autowired
 ReactiveElasticsearchOperations operations;      <.>
 
@@ -161,7 +302,7 @@ ClientConfiguration clientConfiguration = ClientConfiguration.builder()
 
 <.> Define default headers, if they need to be customized
 <.> Use the builder to provide cluster addresses, set default `HttpHeaders` or enable SSL.
-<.> Optionally enable SSL.There exist overloads of this function that can take a `SSLContext` or as an alternative the fingerprint of the certificate as it is output by Elasticsearch 8 on startup.
+<.> Optionally enable SSL.There exist overloads of this function that can take a `SSLContext` or as an alternative the fingerprint of the certificate as it is output by Elasticsearch on startup (since version 8).
 <.> Optionally set a proxy.
 <.> Optionally set a path prefix, mostly used when different clusters a behind some reverse proxy.
 <.> Set the connection timeout.
@@ -183,8 +324,25 @@ In the case this is not enough, the user can add callback functions by using the
 
 The following callbacks are provided:
 
+[[elasticsearch.clients.configuration.callbacks.rest5]]
+==== Configuration of the low level Elasticsearch `Rest5Client`:
+
+This callback provides a `org.elasticsearch.client.RestClientBuilder` that can be used to configure the Elasticsearch
+`Rest5Client`:
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .connectedTo("localhost:9200", "localhost:9291")
+    .withClientConfigurer(Rest5Clients.ElasticsearchRest5ClientConfigurationCallback.from(restClientBuilder -> {
+        // configure the Elasticsearch Rest5Client
+        return restClientBuilder;
+    }))
+    .build();
+----
+====
 [[elasticsearch.clients.configuration.callbacks.rest]]
-==== Configuration of the low level Elasticsearch `RestClient`:
+==== Configuration of the deprecated low level Elasticsearch `RestClient`:
 
 This callback provides a `org.elasticsearch.client.RestClientBuilder` that can be used to configure the Elasticsearch
 `RestClient`:
@@ -193,7 +351,7 @@ This callback provides a `org.elasticsearch.client.RestClientBuilder` that can b
 ----
 ClientConfiguration.builder()
     .connectedTo("localhost:9200", "localhost:9291")
-    .withClientConfigurer(ElasticsearchClients.ElasticsearchRestClientConfigurationCallback.from(restClientBuilder -> {
+    .withClientConfigurer(RestClients.ElasticsearchRestClientConfigurationCallback.from(restClientBuilder -> {
         // configure the Elasticsearch RestClient
         return restClientBuilder;
     }))
@@ -201,10 +359,29 @@ ClientConfiguration.builder()
 ----
 ====
 
-[[elasticsearch.clients.configurationcallbacks.httpasync]]
-==== Configuration of the HttpAsyncClient used by the low level Elasticsearch `RestClient`:
+[[elasticsearch.clients.configurationcallbacks.httpasync5]]
+==== Configuration of the HttpAsyncClient used by the low level Elasticsearch `Rest5Client`:
 
-This callback provides a `org.apache.http.impl.nio.client.HttpAsyncClientBuilder` to configure the HttpCLient that is
+This callback provides a `org.apache.hc.client5.http.impl.async.HttpAsyncClientBuilder` to configure the HttpClient that is
+used by the `Rest5Client`.
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .connectedTo("localhost:9200", "localhost:9291")
+    .withClientConfigurer(Rest5Clients.ElasticsearchHttpClientConfigurationCallback.from(httpAsyncClientBuilder -> {
+        // configure the HttpAsyncClient
+        return httpAsyncClientBuilder;
+    }))
+    .build();
+----
+====
+
+[[elasticsearch.clients.configurationcallbacks.httpasync]]
+==== Configuration of the HttpAsyncClient used by the deprecated low level Elasticsearch `RestClient`:
+
+This callback provides a `org.apache.http.impl.nio.client.HttpAsyncClientBuilder` to configure the HttpClient that is
 used by the `RestClient`.
 
 ====
@@ -212,7 +389,7 @@ used by the `RestClient`.
 ----
 ClientConfiguration.builder()
     .connectedTo("localhost:9200", "localhost:9291")
-    .withClientConfigurer(ElasticsearchClients.ElasticsearchHttpClientConfigurationCallback.from(httpAsyncClientBuilder -> {
+    .withClientConfigurer(RestClients.ElasticsearchHttpClientConfigurationCallback.from(httpAsyncClientBuilder -> {
         // configure the HttpAsyncClient
         return httpAsyncClientBuilder;
     }))
@@ -220,15 +397,92 @@ ClientConfiguration.builder()
 ----
 ====
 
+[[elasticsearch.clients.configurationcallbacks.connectionconfig]]
+==== Configuration of the ConnectionConfig used by the low level Elasticsearch `Rest5Client`:
+
+This callback provides a `org.apache.hc.client5.http.config.ConnectionConfig` to configure the connection that is
+used by the `Rest5Client`.
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .connectedTo("localhost:9200", "localhost:9291")
+    .withClientConfigurer(Rest5Clients.ElasticsearchConnectionConfigurationCallback.from(connectionConfigBuilder -> {
+        // configure the connection
+        return connectionConfigBuilder;
+    }))
+    .build();
+----
+====
+
+[[elasticsearch.clients.configurationcallbacks.connectioncmanager]]
+==== Configuration of the ConnectionManager used by the low level Elasticsearch `Rest5Client`:
+
+This callback provides a `org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder` to configure the connection manager that is
+used by the `Rest5Client`.
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .connectedTo("localhost:9200", "localhost:9291")
+    .withClientConfigurer(Rest5Clients.ElasticsearchConnectionManagerCallback.from(connectionManagerBuilder -> {
+        // configure the connection manager
+        return connectionManagerBuilder;
+    }))
+    .build();
+----
+====
+
+[[elasticsearch.clients.configurationcallbacks.requestconfig]]
+==== Configuration of the RequestConfig used by the low level Elasticsearch `Rest5Client`:
+
+This callback provides a `org.apache.hc.client5.http.config.RequestConfig` to configure the RequestConfig that is
+used by the `Rest5Client`.
+
+====
+[source,java]
+----
+ClientConfiguration.builder()
+    .connectedTo("localhost:9200", "localhost:9291")
+    .withClientConfigurer(Rest5Clients.ElasticsearchRequestConfigCallback.from(requestConfigBuilder -> {
+        // configure the request config
+        return requestConfigBuilder;
+    }))
+    .build();
+----
+====
+
 [[elasticsearch.clients.logging]]
 == Client Logging
 
 To see what is actually sent to and received from the server `Request` / `Response` logging on the transport level needs to be turned on as outlined in the snippet below.
-This can be enabled in the Elasticsearch client by setting the level of the `tracer` package to "trace" (see
-https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/current/java-rest-low-usage-logging.html)
+This can be enabled in the Elasticsearch client by setting the level of the `co.elastic.clients.transport.rest5_client.low_level.Request` package to "trace" (see
+https://www.elastic.co/docs/reference/elasticsearch/clients/java/transport/rest5-client/usage/logging)
 
 .Enable transport layer logging
+[tabs]
+======
+XML::
++
 [source,xml]
 ----
-<logger name="tracer" level="trace"/>
+<logger name="co.elastic.clients.transport.rest5_client.low_level.Request" level="trace"/>
 ----
+
+yml::
++
+[source,yml]
+----
+logging.level:
+  co.elastic.clients.transport.rest5_client.low_level.Request: trace
+----
+
+ini::
++
+[source,ini]
+----
+logging.level.co.elastic.clients.transport.rest5_client.low_level.Request=trace
+----
+======

src/main/antora/modules/ROOT/pages/elasticsearch/elasticsearch-new.adoc

@@ -1,6 +1,24 @@
 [[new-features]]
 = What's new
 
+[[new-features.6-1-0]]
+== New in Spring Data Elasticsearch 6.1
+
+* Upgrade to Elasticsearch 9.3.3/ Client 9.3.4
+* Add support to use `IndexCoordinates` as repository query parameter
+* Add support for includeNamedQueriesScore in Query
+* Add support for Micrometer observation.
+
+[[new-features.6-0-0]]
+== New in Spring Data Elasticsearch 6.0
+
+* Upgrade to Spring 7
+* Switch to jspecify nullability annotations
+* Upgrade to Elasticsearch 9.2.1
+* Use the new Elasticsearch Rest5Client as default
+* Add support for SpEL expressions in the `settingPath` parameter of the `@Setting` annotation
+
+
 [[new-features.5-5-0]]
 == New in Spring Data Elasticsearch 5.5
 

src/main/antora/modules/ROOT/pages/elasticsearch/misc.adoc

@@ -11,7 +11,7 @@ When creating Elasticsearch indices with Spring Data Elasticsearch different ind
 The following arguments are available:
 
 * `useServerConfiguration` does not send any settings parameters, so the Elasticsearch server configuration determines them.
-* `settingPath` refers to a JSON file defining the settings that must be resolvable in the classpath
+* `settingPath` refers to a JSON file defining the settings that must be resolvable in the classpath, it is possible to use a SpEL expression here
 * `shards` the number of shards to use, defaults to _1_
 * `replicas` the number of replicas, defaults to _1_
 * `refreshIntervall`, defaults to _"1s"_

src/main/antora/modules/ROOT/pages/elasticsearch/scripted-and-runtime-fields.adoc

@@ -20,12 +20,12 @@ Whereas the birthdate is fix, the age depends on the time when a query is issued
 ====
 [source,java]
 ----
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.annotation.Id;
 import org.springframework.data.elasticsearch.annotations.DateFormat;
 import org.springframework.data.elasticsearch.annotations.Document;
 import org.springframework.data.elasticsearch.annotations.Field;
 import org.springframework.data.elasticsearch.annotations.ScriptedField;
-import org.springframework.lang.Nullable;
 
 import java.time.LocalDate;
 import java.time.format.DateTimeFormatter;

src/main/antora/modules/ROOT/pages/elasticsearch/versions.adoc

@@ -6,9 +6,11 @@ The following table shows the Elasticsearch and Spring versions that are used by
 [cols="^,^,^,^",options="header"]
 |===
 | Spring Data Release Train | Spring Data Elasticsearch | Elasticsearch | Spring Framework
-| 2025.0 | 5.5.x | 8.18.8 | 6.2.x
-| 2024.1 | 5.4.x | 8.15.5 | 6.1.x
-| 2024.0 | 5.3.xfootnote:oom[Out of maintenance] | 8.13.4 | 6.1.x
+| 2026.0 | 6.1.x | 9.3.4 | 7.0.x
+| 2025.1 | 6.0.x | 9.2.2 | 7.0.x
+| 2025.0 | 5.5.x | 8.18.1 | 6.2.x
+| 2024.1 | 5.4.xfootnote:oom[Out of maintenance] | 8.15.5 | 6.1.x
+| 2024.0 | 5.3.xfootnote:oom[] | 8.13.4 | 6.1.x
 | 2023.1 (Vaughan) | 5.2.xfootnote:oom[] | 8.11.1 | 6.1.x
 | 2023.0 (Ullmann) | 5.1.xfootnote:oom[] | 8.7.1 | 6.0.x
 | 2022.0 (Turing) | 5.0.xfootnote:oom[] | 8.5.3 | 6.0.x

src/main/antora/modules/ROOT/pages/migration-guides/migration-guide-5.5-6.0.adoc

@@ -0,0 +1,27 @@
+[[elasticsearch-migration-guide-5.5-6.0]]
+= Upgrading from 5.5.x to 6.0.x
+
+This section describes breaking changes from version 5.5.x to 6.0.x and how removed features can be replaced by new introduced features.
+
+[[elasticsearch-migration-guide-5.5-6.0.breaking-changes]]
+== Breaking Changes
+
+From version 6.0 on, Spring Data Elasticsearch uses the Elasticsearch 9 libraries and as default the new `Rest5Client` provided by these libraries. It is still possible to use the old `RestClient`, check xref:elasticsearch/clients.adoc[Elasticsearch clients] for information. The configuration callbacks for this `RestClient` have been moved from `org.springframework.data.elasticsearch.client.elc.ElasticsearchClients` to the `org.springframework.data.elasticsearch.client.elc.rest_client.RestClients` class.
+
+In the `org.springframework.data.elasticsearch.core.query.UpdateQuery` class the type of the two fields `ifSeqNo` and `ifPrimaryTerm` has changed from `Integer` to `Long` to align with the normal query and the underlying Elasticsearch client.
+
+[[elasticsearch-migration-guide-5.5-6.0.deprecations]]
+== Deprecations
+
+All the code using the old `RestClient` has been moved to the `org.springframework.data.elasticsearch.client.elc.rest_client` package and has been deprecated. Users should switch to the classes from the `org.springframework.data.elasticsearch.client.elc.rest5_client` package.
+
+
+=== Removals
+
+The `org.springframework.data.elasticsearch.core.query.ScriptType` enum has been removed. To distinguish between an inline and a stored script set the appropriate values in the `org.springframework.data.elasticsearch.core.query.ScriptData` record.
+
+These methods have been removed because the Elasticsearch Client 9 does not support them anymore:
+```
+org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchIndicesClient.unfreeze(UnfreezeRequest)
+org.springframework.data.elasticsearch.client.elc.ReactiveElasticsearchIndicesClient.unfreeze(Function<UnfreezeRequest.Builder, ObjectBuilder<UnfreezeRequest>>)
+```

src/main/antora/modules/ROOT/pages/repositories/projections.adoc

@@ -1,4 +1,13 @@
 [[elasticsearch.projections]]
 = Projections
 
+[[elasticsearch.projections.limitations]]
+== Spring Data Elasticsearch Projection Limitations
+
+This chapter is pulled in from the Spring Data Commons documentation, but does not apply to Spring Data Elasticsearch.
+
+IMPORTANT: Interface-based projections are not supported in Spring Data Elasticsearch repository query methods.
+
+To limit the fields returned from Elasticsearch, use the xref:elasticsearch/repositories/elasticsearch-repositories.adoc#elasticsearch.repositories.annotations.sourcefilters[`@SourceFilters`] annotation on your repository methods instead.
+
 include::{commons}@data-commons::page$repositories/projections.adoc[leveloffset=+1]

src/main/java/org/springframework/data/elasticsearch/ElasticsearchErrorCause.java

@@ -15,10 +15,10 @@
  */
 package org.springframework.data.elasticsearch;
 
-import org.springframework.lang.Nullable;
-
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Object describing an Elasticsearch error
  *
@@ -26,8 +26,7 @@ import java.util.List;
  * @since 4.4
  */
 public class ElasticsearchErrorCause {
-	@Nullable
-	private final String type;
+	@Nullable private final String type;
 
 	private final String reason;
 

src/main/java/org/springframework/data/elasticsearch/UncategorizedElasticsearchException.java

@@ -15,8 +15,8 @@
  */
 package org.springframework.data.elasticsearch;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.dao.UncategorizedDataAccessException;
-import org.springframework.lang.Nullable;
 
 /**
  * @author Peter-Josef Meisch

src/main/java/org/springframework/data/elasticsearch/annotations/Document.java

@@ -107,17 +107,15 @@ public @interface Document {
 	 */
 	Alias[] aliases() default {};
 
-	/**
+    /**
+     * Note: the enum value FORCE, which was introduced in 4.4 has been removed
+     * again by Elasticsearch.
 	 * @since 4.3
 	 */
 	enum VersionType {
 		INTERNAL("internal"), //
 		EXTERNAL("external"), //
-		EXTERNAL_GTE("external_gte"), //
-		/**
-		 * @since 4.4
-		 */
-		FORCE("force");
+		EXTERNAL_GTE("external_gte"); //
 
 		private final String esName;
 

src/main/java/org/springframework/data/elasticsearch/annotations/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.annotations;

src/main/java/org/springframework/data/elasticsearch/aot/ElasticsearchAotPredicates.java

@@ -17,7 +17,7 @@ package org.springframework.data.elasticsearch.aot;
 
 import java.util.function.Predicate;
 
-import org.springframework.data.util.ReactiveWrappers;
+import org.springframework.data.core.ReactiveWrappers;
 
 /**
  * @author Peter-Josef Meisch

src/main/java/org/springframework/data/elasticsearch/aot/SpringDataElasticsearchRuntimeHints.java

@@ -19,6 +19,7 @@ import static org.springframework.data.elasticsearch.aot.ElasticsearchAotPredica
 
 import java.util.Arrays;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.aot.hint.MemberCategory;
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
@@ -32,7 +33,6 @@ import org.springframework.data.elasticsearch.core.event.ReactiveAfterConvertCal
 import org.springframework.data.elasticsearch.core.event.ReactiveAfterLoadCallback;
 import org.springframework.data.elasticsearch.core.event.ReactiveAfterSaveCallback;
 import org.springframework.data.elasticsearch.core.event.ReactiveBeforeConvertCallback;
-import org.springframework.lang.Nullable;
 
 /**
  * @author Peter-Josef Meisch

src/main/java/org/springframework/data/elasticsearch/aot/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.aot;

src/main/java/org/springframework/data/elasticsearch/client/ClientConfiguration.java

@@ -25,8 +25,8 @@ import java.util.function.Supplier;
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLContext;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.support.HttpHeaders;
-import org.springframework.lang.Nullable;
 
 /**
  * Configuration interface exposing common client configuration properties for Elasticsearch clients.
@@ -127,10 +127,16 @@ public interface ClientConfiguration {
 	Optional<String> getCaFingerprint();
 
 	/**
-	 * Returns the {@link HostnameVerifier} to use. Can be {@link Optional#empty()} if not configured.
+	 * Returns the {@link HostnameVerifier} to use. Must be {@link Optional#empty()} if not configured.
+	 * Cannot be used with the Rest5Client used from Elasticsearch 9 on as the underlying Apache http components 5 does not offer a way
+	 * to set this. Users that need a hostname verifier must integrate this in a SSLContext.
+	 * Returning a value here is ignored in this case
 	 *
 	 * @return the {@link HostnameVerifier} to use. Can be {@link Optional#empty()} if not configured.
+	 * @deprecated since 6.0
 	 */
+	// todo #3117 document this
+	@Deprecated(since = "6.0", forRemoval=true)
 	Optional<HostnameVerifier> getHostNameVerifier();
 
 	/**

src/main/java/org/springframework/data/elasticsearch/client/ClientConfigurationBuilder.java

@@ -25,11 +25,11 @@ import java.util.function.Supplier;
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLContext;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationBuilderWithRequiredEndpoint;
 import org.springframework.data.elasticsearch.client.ClientConfiguration.MaybeSecureClientConfigurationBuilder;
 import org.springframework.data.elasticsearch.client.ClientConfiguration.TerminalClientConfigurationBuilder;
 import org.springframework.data.elasticsearch.support.HttpHeaders;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/DefaultClientConfiguration.java

@@ -24,9 +24,8 @@ import java.util.function.Supplier;
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLContext;
 
-import org.elasticsearch.client.RestClientBuilder.HttpClientConfigCallback;
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.support.HttpHeaders;
-import org.springframework.lang.Nullable;
 
 /**
  * Default {@link ClientConfiguration} implementation.

src/main/java/org/springframework/data/elasticsearch/client/elc/AbstractQueryProcessor.java

@@ -17,10 +17,10 @@ package org.springframework.data.elasticsearch.client.elc;
 
 import java.util.function.Consumer;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.query.CriteriaQuery;
 import org.springframework.data.elasticsearch.core.query.Query;
 import org.springframework.data.elasticsearch.core.query.StringQuery;
-import org.springframework.lang.Nullable;
 
 /**
  * An abstract class that serves as a base for query processors. It provides a common interface and basic functionality
@@ -38,8 +38,8 @@ public abstract class AbstractQueryProcessor {
 	 * @param queryConverter correct mapped field names and the values to the converted values.
 	 * @return an Elasticsearch {@literal query}.
 	 */
-	@Nullable
-	static co.elastic.clients.elasticsearch._types.query_dsl.Query getEsQuery(@Nullable Query query,
+
+	static co.elastic.clients.elasticsearch._types.query_dsl.@Nullable Query getEsQuery(@Nullable Query query,
 			@Nullable Consumer<Query> queryConverter) {
 		if (query == null) {
 			return null;

src/main/java/org/springframework/data/elasticsearch/client/elc/CriteriaQueryProcessor.java

@@ -31,13 +31,13 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.annotations.FieldType;
 import org.springframework.data.elasticsearch.core.query.Criteria;
 import org.springframework.data.elasticsearch.core.query.Field;
 import org.springframework.data.elasticsearch.core.query.HasChildQuery;
 import org.springframework.data.elasticsearch.core.query.HasParentQuery;
 import org.springframework.data.elasticsearch.core.query.InnerHitsQuery;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/elc/DefaultElasticsearchObservationConvention.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import io.micrometer.common.KeyValues;
+
+/**
+ * Default {@link ElasticsearchObservationConvention} implementation.
+ *
+ * @author maryantocinn
+ * @since 6.1
+ */
+public class DefaultElasticsearchObservationConvention implements ElasticsearchObservationConvention {
+
+	public static final DefaultElasticsearchObservationConvention INSTANCE = new DefaultElasticsearchObservationConvention();
+
+	@Override
+	public String getName() {
+		return ElasticsearchObservation.ELASTICSEARCH_COMMAND_OBSERVATION.getName();
+	}
+
+	@Override
+	public String getContextualName(ElasticsearchObservationContext context) {
+
+		String indexName = context.getIndexName();
+		if (indexName != null) {
+			return context.getOperationName().getValue() + " " + indexName;
+		}
+		return context.getOperationName().getValue();
+	}
+
+	@Override
+	public KeyValues getLowCardinalityKeyValues(ElasticsearchObservationContext context) {
+
+		KeyValues keyValues = KeyValues.of(
+				ElasticsearchObservation.LowCardinalityKeyNames.OPERATION.withValue(context.getOperationName().getValue()));
+
+		String indexName = context.getIndexName();
+		if (indexName != null) {
+			keyValues = keyValues.and(ElasticsearchObservation.LowCardinalityKeyNames.COLLECTION.withValue(indexName));
+		}
+
+		return keyValues;
+	}
+
+	@Override
+	public KeyValues getHighCardinalityKeyValues(ElasticsearchObservationContext context) {
+
+		Integer batchSize = context.getBatchSize();
+		if (batchSize != null) {
+			return KeyValues.of(
+					ElasticsearchObservation.HighCardinalityKeyNames.BATCH_SIZE.withValue(String.valueOf(batchSize)));
+		}
+
+		return KeyValues.empty();
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/DocumentAdapters.java

@@ -24,16 +24,9 @@ import co.elastic.clients.elasticsearch.core.search.Hit;
 import co.elastic.clients.elasticsearch.core.search.NestedIdentity;
 import co.elastic.clients.json.JsonData;
 import co.elastic.clients.json.JsonpMapper;
-
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.function.Function;
-import java.util.stream.Collectors;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.MultiGetItem;
 import org.springframework.data.elasticsearch.core.document.Document;
 import org.springframework.data.elasticsearch.core.document.Explanation;
@@ -41,9 +34,15 @@ import org.springframework.data.elasticsearch.core.document.NestedMetaData;
 import org.springframework.data.elasticsearch.core.document.SearchDocument;
 import org.springframework.data.elasticsearch.core.document.SearchDocumentAdapter;
 import org.springframework.data.elasticsearch.core.document.SearchDocumentResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
 /**
  * Utility class to adapt different Elasticsearch responses to a
  * {@link org.springframework.data.elasticsearch.core.document.Document}
@@ -55,187 +54,188 @@ import org.springframework.util.Assert;
  */
 final class DocumentAdapters {
 
-	private static final Log LOGGER = LogFactory.getLog(DocumentAdapters.class);
+    private static final Log LOGGER = LogFactory.getLog(DocumentAdapters.class);
 
-	private DocumentAdapters() {}
+    private DocumentAdapters() {
+    }
 
-	/**
-	 * Creates a {@link SearchDocument} from a {@link Hit} returned by the Elasticsearch client.
-	 *
-	 * @param hit the hit object
-	 * @param jsonpMapper to map JsonData objects
-	 * @return the created {@link SearchDocument}
-	 */
-	public static SearchDocument from(Hit<?> hit, JsonpMapper jsonpMapper) {
+    /**
+     * Creates a {@link SearchDocument} from a {@link Hit} returned by the Elasticsearch client.
+     *
+     * @param hit         the hit object
+     * @param jsonpMapper to map JsonData objects
+     * @return the created {@link SearchDocument}
+     */
+    public static SearchDocument from(Hit<?> hit, JsonpMapper jsonpMapper) {
 
-		Assert.notNull(hit, "hit must not be null");
+        Assert.notNull(hit, "hit must not be null");
 
-		Map<String, List<String>> highlightFields = hit.highlight();
+        Map<String, List<String>> highlightFields = hit.highlight();
 
-		Map<String, SearchDocumentResponse> innerHits = new LinkedHashMap<>();
-		hit.innerHits().forEach((name, innerHitsResult) -> {
-			// noinspection ReturnOfNull
-			innerHits.put(name, SearchDocumentResponseBuilder.from(innerHitsResult.hits(), null, null, null, 0, null, null,
-					searchDocument -> null, jsonpMapper));
-		});
+        Map<String, SearchDocumentResponse> innerHits = new LinkedHashMap<>();
+        hit.innerHits().forEach((name, innerHitsResult) -> {
+            // noinspection ReturnOfNull
+            innerHits.put(name, SearchDocumentResponseBuilder.from(innerHitsResult.hits(), null, null, null, 0, null, null,
+                    searchDocument -> null, jsonpMapper));
+        });
 
-		NestedMetaData nestedMetaData = from(hit.nested());
+        NestedMetaData nestedMetaData = from(hit.nested());
 
-		Explanation explanation = from(hit.explanation());
+        Explanation explanation = from(hit.explanation());
 
-		List<String> matchedQueries = hit.matchedQueries();
+        Map<String, Double> matchedQueries = hit.matchedQueries();
 
-		Function<Map<String, JsonData>, EntityAsMap> fromFields = fields -> {
-			StringBuilder sb = new StringBuilder("{");
-			final boolean[] firstField = { true };
-			hit.fields().forEach((key, jsonData) -> {
-				if (!firstField[0]) {
-					sb.append(',');
-				}
-				sb.append('"').append(key).append("\":") //
-						.append(jsonData.toJson(jsonpMapper).toString());
-				firstField[0] = false;
-			});
-			sb.append('}');
-			return new EntityAsMap().fromJson(sb.toString());
-		};
+        Function<Map<String, JsonData>, EntityAsMap> fromFields = fields -> {
+            StringBuilder sb = new StringBuilder("{");
+            final boolean[] firstField = {true};
+            hit.fields().forEach((key, jsonData) -> {
+                if (!firstField[0]) {
+                    sb.append(',');
+                }
+                sb.append('"').append(key).append("\":") //
+                        .append(jsonData.toJson(jsonpMapper).toString());
+                firstField[0] = false;
+            });
+            sb.append('}');
+            return new EntityAsMap().fromJson(sb.toString());
+        };
 
-		EntityAsMap hitFieldsAsMap = fromFields.apply(hit.fields());
+        EntityAsMap hitFieldsAsMap = fromFields.apply(hit.fields());
 
-		Map<String, List<Object>> documentFields = new LinkedHashMap<>();
-		hitFieldsAsMap.forEach((key, value) -> {
-			if (value instanceof List) {
-				// noinspection unchecked
-				documentFields.put(key, (List<Object>) value);
-			} else {
-				documentFields.put(key, Collections.singletonList(value));
-			}
-		});
+        Map<String, List<Object>> documentFields = new LinkedHashMap<>();
+        hitFieldsAsMap.forEach((key, value) -> {
+            if (value instanceof List) {
+                // noinspection unchecked
+                documentFields.put(key, (List<Object>) value);
+            } else {
+                documentFields.put(key, Collections.singletonList(value));
+            }
+        });
 
-		Document document;
-		Object source = hit.source();
-		if (source == null) {
-			document = Document.from(hitFieldsAsMap);
-		} else {
-			if (source instanceof EntityAsMap entityAsMap) {
-				document = Document.from(entityAsMap);
-			} else if (source instanceof JsonData jsonData) {
-				document = Document.from(jsonData.to(EntityAsMap.class));
-			} else {
+        Document document;
+        Object source = hit.source();
+        if (source == null) {
+            document = Document.from(hitFieldsAsMap);
+        } else {
+            if (source instanceof EntityAsMap entityAsMap) {
+                document = Document.from(entityAsMap);
+            } else if (source instanceof JsonData jsonData) {
+                document = Document.from(jsonData.to(EntityAsMap.class));
+            } else {
 
-				if (LOGGER.isWarnEnabled()) {
-					LOGGER.warn(String.format("Cannot map from type " + source.getClass().getName()));
-				}
-				document = Document.create();
-			}
-		}
-		document.setIndex(hit.index());
-		document.setId(hit.id());
+                if (LOGGER.isWarnEnabled()) {
+                    LOGGER.warn(String.format("Cannot map from type " + source.getClass().getName()));
+                }
+                document = Document.create();
+            }
+        }
+        document.setIndex(hit.index());
+        document.setId(hit.id());
 
-		if (hit.version() != null) {
-			document.setVersion(hit.version());
-		}
-		document.setSeqNo(hit.seqNo() != null && hit.seqNo() >= 0 ? hit.seqNo() : -2); // -2 was the default value in the
-		// old client
-		document.setPrimaryTerm(hit.primaryTerm() != null && hit.primaryTerm() > 0 ? hit.primaryTerm() : 0);
+        if (hit.version() != null) {
+            document.setVersion(hit.version());
+        }
+        document.setSeqNo(hit.seqNo() != null && hit.seqNo() >= 0 ? hit.seqNo() : -2); // -2 was the default value in the
+        // old client
+        document.setPrimaryTerm(hit.primaryTerm() != null && hit.primaryTerm() > 0 ? hit.primaryTerm() : 0);
 
-		float score = hit.score() != null ? hit.score().floatValue() : Float.NaN;
-		return new SearchDocumentAdapter(document, score, hit.sort().stream().map(TypeUtils::toObject).toArray(),
-				documentFields, highlightFields, innerHits, nestedMetaData, explanation, matchedQueries, hit.routing());
-	}
+        float score = hit.score() != null ? hit.score().floatValue() : Float.NaN;
+        return new SearchDocumentAdapter(document, score, hit.sort().stream().map(TypeUtils::toObject).toArray(),
+                documentFields, highlightFields, innerHits, nestedMetaData, explanation, matchedQueries, hit.routing());
+    }
 
-	public static SearchDocument from(CompletionSuggestOption<EntityAsMap> completionSuggestOption) {
+    public static SearchDocument from(CompletionSuggestOption<EntityAsMap> completionSuggestOption) {
 
-		Document document = completionSuggestOption.source() != null ? Document.from(completionSuggestOption.source())
-				: Document.create();
-		document.setIndex(completionSuggestOption.index());
+        Document document = completionSuggestOption.source() != null ? Document.from(completionSuggestOption.source())
+                : Document.create();
+        document.setIndex(completionSuggestOption.index());
 
-		if (completionSuggestOption.id() != null) {
-			document.setId(completionSuggestOption.id());
-		}
+        if (completionSuggestOption.id() != null) {
+            document.setId(completionSuggestOption.id());
+        }
 
-		float score = completionSuggestOption.score() != null ? completionSuggestOption.score().floatValue() : Float.NaN;
-		return new SearchDocumentAdapter(document, score, new Object[] {}, Collections.emptyMap(), Collections.emptyMap(),
-				Collections.emptyMap(), null, null, null, completionSuggestOption.routing());
-	}
+        float score = completionSuggestOption.score() != null ? completionSuggestOption.score().floatValue() : Float.NaN;
+        return new SearchDocumentAdapter(document, score, new Object[]{}, Collections.emptyMap(), Collections.emptyMap(),
+                Collections.emptyMap(), null, null, null, completionSuggestOption.routing());
+    }
 
-	@Nullable
-	private static Explanation from(@Nullable co.elastic.clients.elasticsearch.core.explain.Explanation explanation) {
+    @Nullable
+    private static Explanation from(co.elastic.clients.elasticsearch.core.explain.@Nullable Explanation explanation) {
 
-		if (explanation == null) {
-			return null;
-		}
-		List<Explanation> details = explanation.details().stream().map(DocumentAdapters::from).collect(Collectors.toList());
-		return new Explanation(true, (double) explanation.value(), explanation.description(), details);
-	}
+        if (explanation == null) {
+            return null;
+        }
+        List<Explanation> details = explanation.details().stream().map(DocumentAdapters::from).collect(Collectors.toList());
+        return new Explanation(true, (double) explanation.value(), explanation.description(), details);
+    }
 
-	private static Explanation from(ExplanationDetail explanationDetail) {
+    private static Explanation from(ExplanationDetail explanationDetail) {
 
-		List<Explanation> details = explanationDetail.details().stream().map(DocumentAdapters::from)
-				.collect(Collectors.toList());
-		return new Explanation(null, (double) explanationDetail.value(), explanationDetail.description(), details);
-	}
+        List<Explanation> details = explanationDetail.details().stream().map(DocumentAdapters::from)
+                .collect(Collectors.toList());
+        return new Explanation(null, (double) explanationDetail.value(), explanationDetail.description(), details);
+    }
 
-	@Nullable
-	private static NestedMetaData from(@Nullable NestedIdentity nestedIdentity) {
+    @Nullable
+    private static NestedMetaData from(@Nullable NestedIdentity nestedIdentity) {
 
-		if (nestedIdentity == null) {
-			return null;
-		}
+        if (nestedIdentity == null) {
+            return null;
+        }
 
-		NestedMetaData child = from(nestedIdentity.nested());
-		return NestedMetaData.of(nestedIdentity.field(), nestedIdentity.offset(), child);
-	}
+        NestedMetaData child = from(nestedIdentity.nested());
+        return NestedMetaData.of(nestedIdentity.field(), nestedIdentity.offset(), child);
+    }
 
-	/**
-	 * Creates a {@link Document} from a {@link GetResponse} where the found document is contained as {@link EntityAsMap}.
-	 *
-	 * @param getResponse the response instance
-	 * @return the Document
-	 */
-	@Nullable
-	public static Document from(GetResult<EntityAsMap> getResponse) {
+    /**
+     * Creates a {@link Document} from a {@link GetResponse} where the found document is contained as {@link EntityAsMap}.
+     *
+     * @param getResponse the response instance
+     * @return the Document
+     */
+    @Nullable
+    public static Document from(GetResult<EntityAsMap> getResponse) {
 
-		Assert.notNull(getResponse, "getResponse must not be null");
+        Assert.notNull(getResponse, "getResponse must not be null");
 
-		if (!getResponse.found()) {
-			return null;
-		}
+        if (!getResponse.found()) {
+            return null;
+        }
 
-		Document document = getResponse.source() != null ? Document.from(getResponse.source()) : Document.create();
-		document.setIndex(getResponse.index());
-		document.setId(getResponse.id());
+        Document document = getResponse.source() != null ? Document.from(getResponse.source()) : Document.create();
+        document.setIndex(getResponse.index());
+        document.setId(getResponse.id());
 
-		if (getResponse.version() != null) {
-			document.setVersion(getResponse.version());
-		}
+        if (getResponse.version() != null) {
+            document.setVersion(getResponse.version());
+        }
 
-		if (getResponse.seqNo() != null) {
-			document.setSeqNo(getResponse.seqNo());
-		}
+        if (getResponse.seqNo() != null) {
+            document.setSeqNo(getResponse.seqNo());
+        }
 
-		if (getResponse.primaryTerm() != null) {
-			document.setPrimaryTerm(getResponse.primaryTerm());
-		}
+        if (getResponse.primaryTerm() != null) {
+            document.setPrimaryTerm(getResponse.primaryTerm());
+        }
 
-		return document;
-	}
+        return document;
+    }
 
-	/**
-	 * Creates a list of {@link MultiGetItem}s from a {@link MgetResponse} where the data is contained as
-	 * {@link EntityAsMap} instances.
-	 *
-	 * @param mgetResponse the response instance
-	 * @return list of multiget items
-	 */
-	public static List<MultiGetItem<Document>> from(MgetResponse<EntityAsMap> mgetResponse) {
+    /**
+     * Creates a list of {@link MultiGetItem}s from a {@link MgetResponse} where the data is contained as
+     * {@link EntityAsMap} instances.
+     *
+     * @param mgetResponse the response instance
+     * @return list of multiget items
+     */
+    public static List<MultiGetItem<Document>> from(MgetResponse<EntityAsMap> mgetResponse) {
 
-		Assert.notNull(mgetResponse, "mgetResponse must not be null");
+        Assert.notNull(mgetResponse, "mgetResponse must not be null");
 
-		return mgetResponse.docs().stream() //
-				.map(itemResponse -> MultiGetItem.of( //
-						itemResponse.isFailure() ? null : from(itemResponse.result()), //
-						ResponseConverter.getFailure(itemResponse)))
-				.collect(Collectors.toList());
-	}
+        return mgetResponse.docs().stream() //
+                .map(itemResponse -> MultiGetItem.of( //
+                        itemResponse.isFailure() ? null : from(itemResponse.result()), //
+                        ResponseConverter.getFailure(itemResponse)))
+                .collect(Collectors.toList());
+    }
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchAggregations.java

@@ -22,8 +22,8 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.AggregationsContainer;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchClientFactoryBean.java

@@ -19,12 +19,12 @@ import co.elastic.clients.elasticsearch.ElasticsearchClient;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.FactoryBeanNotInitializedException;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.data.elasticsearch.client.ClientConfiguration;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchClients.java

@@ -15,44 +15,38 @@
  */
 package org.springframework.data.elasticsearch.client.elc;
 
+import static org.springframework.data.elasticsearch.client.elc.rest5_client.Rest5Clients.*;
+import static org.springframework.data.elasticsearch.client.elc.rest_client.RestClients.*;
+
 import co.elastic.clients.elasticsearch.ElasticsearchClient;
 import co.elastic.clients.json.JsonpMapper;
 import co.elastic.clients.json.jackson.JacksonJsonpMapper;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.TransportOptions;
-import co.elastic.clients.transport.TransportUtils;
 import co.elastic.clients.transport.Version;
+import co.elastic.clients.transport.rest5_client.Rest5ClientOptions;
+import co.elastic.clients.transport.rest5_client.Rest5ClientTransport;
+import co.elastic.clients.transport.rest5_client.low_level.RequestOptions;
+import co.elastic.clients.transport.rest5_client.low_level.Rest5Client;
 import co.elastic.clients.transport.rest_client.RestClientOptions;
 import co.elastic.clients.transport.rest_client.RestClientTransport;
 
-import java.net.InetSocketAddress;
-import java.time.Duration;
-import java.util.Arrays;
-import java.util.List;
 import java.util.function.Consumer;
 import java.util.function.Function;
-import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
-import org.apache.http.HttpHost;
-import org.apache.http.HttpRequest;
-import org.apache.http.HttpRequestInterceptor;
-import org.apache.http.client.config.RequestConfig;
 import org.apache.http.entity.ContentType;
 import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
-import org.apache.http.message.BasicHeader;
 import org.apache.http.message.BasicNameValuePair;
-import org.apache.http.protocol.HttpContext;
-import org.elasticsearch.client.RequestOptions;
 import org.elasticsearch.client.RestClient;
-import org.elasticsearch.client.RestClientBuilder;
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.client.ClientConfiguration;
-import org.springframework.data.elasticsearch.support.HttpHeaders;
-import org.springframework.lang.Nullable;
+import org.springframework.data.elasticsearch.support.VersionInfo;
 import org.springframework.util.Assert;
 
 /**
- * Utility class to create the different Elasticsearch clients
+ * Utility class to create the different Elasticsearch clients. The RestClient class is the one used in Elasticsearch
+ * until version 9, it is still available, but it's use is deprecated. The Rest5Client class is the one that should be
+ * used from Elasticsearch 9 on.
  *
  * @author Peter-Josef Meisch
  * @since 4.4
@@ -119,18 +113,32 @@ public final class ElasticsearchClients {
 	 *
 	 * @param restClient the underlying {@link RestClient}
 	 * @return the {@link ReactiveElasticsearchClient}
+	 * @deprecated since 6.0, use the version with a Rest5Client.
 	 */
+	@Deprecated(since = "6.0", forRemoval = true)
 	public static ReactiveElasticsearchClient createReactive(RestClient restClient) {
 		return createReactive(restClient, null, DEFAULT_JSONP_MAPPER);
 	}
 
+	/**
+	 * Creates a new {@link ReactiveElasticsearchClient}.
+	 *
+	 * @param rest5Client the underlying {@link RestClient}
+	 * @return the {@link ReactiveElasticsearchClient}
+	 */
+	public static ReactiveElasticsearchClient createReactive(Rest5Client rest5Client) {
+		return createReactive(rest5Client, null, DEFAULT_JSONP_MAPPER);
+	}
+
 	/**
 	 * Creates a new {@link ReactiveElasticsearchClient}.
 	 *
 	 * @param restClient the underlying {@link RestClient}
 	 * @param transportOptions options to be added to each request.
 	 * @return the {@link ReactiveElasticsearchClient}
+	 * @deprecated since 6.0, use the version with a Rest5Client.
 	 */
+	@Deprecated(since = "6.0", forRemoval = true)
 	public static ReactiveElasticsearchClient createReactive(RestClient restClient,
 			@Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
 
@@ -139,6 +147,21 @@ public final class ElasticsearchClients {
 		var transport = getElasticsearchTransport(restClient, REACTIVE_CLIENT, transportOptions, jsonpMapper);
 		return createReactive(transport);
 	}
+	/**
+	 * Creates a new {@link ReactiveElasticsearchClient}.
+	 *
+	 * @param rest5Client the underlying {@link RestClient}
+	 * @param transportOptions options to be added to each request.
+	 * @return the {@link ReactiveElasticsearchClient}
+	 */
+	public static ReactiveElasticsearchClient createReactive(Rest5Client rest5Client,
+			@Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
+
+		Assert.notNull(rest5Client, "restClient must not be null");
+
+		var transport = getElasticsearchTransport(rest5Client, REACTIVE_CLIENT, transportOptions, jsonpMapper);
+		return createReactive(transport);
+	}
 
 	/**
 	 * Creates a new {@link ReactiveElasticsearchClient} that uses the given {@link ElasticsearchTransport}.
@@ -156,17 +179,21 @@ public final class ElasticsearchClients {
 
 	// region imperative client
 	/**
-	 * Creates a new imperative {@link ElasticsearchClient}
+	 * Creates a new imperative {@link ElasticsearchClient}. This uses a RestClient, if the old RestClient is needed, this
+	 * must be created with the {@link org.springframework.data.elasticsearch.client.elc.rest_client.RestClients} class
+	 * and passed in as parameter.
 	 *
 	 * @param clientConfiguration configuration options, must not be {@literal null}.
 	 * @return the {@link ElasticsearchClient}
 	 */
 	public static ElasticsearchClient createImperative(ClientConfiguration clientConfiguration) {
-		return createImperative(getRestClient(clientConfiguration), null, DEFAULT_JSONP_MAPPER);
+		return createImperative(getRest5Client(clientConfiguration), null, DEFAULT_JSONP_MAPPER);
 	}
 
 	/**
-	 * Creates a new imperative {@link ElasticsearchClient}
+	 * Creates a new imperative {@link ElasticsearchClient}. This uses a RestClient, if the old RestClient is needed, this
+	 * must be created with the {@link org.springframework.data.elasticsearch.client.elc.rest_client.RestClients} class
+	 * and passed in as parameter.
 	 *
 	 * @param clientConfiguration configuration options, must not be {@literal null}.
 	 * @param transportOptions options to be added to each request.
@@ -174,7 +201,7 @@ public final class ElasticsearchClients {
 	 */
 	public static ElasticsearchClient createImperative(ClientConfiguration clientConfiguration,
 			TransportOptions transportOptions) {
-		return createImperative(getRestClient(clientConfiguration), transportOptions, DEFAULT_JSONP_MAPPER);
+		return createImperative(getRest5Client(clientConfiguration), transportOptions, DEFAULT_JSONP_MAPPER);
 	}
 
 	/**
@@ -182,11 +209,23 @@ public final class ElasticsearchClients {
 	 *
 	 * @param restClient the RestClient to use
 	 * @return the {@link ElasticsearchClient}
+	 * @deprecated since 6.0, use the version with a Rest5Client.
 	 */
+	@Deprecated(since = "6.0", forRemoval = true)
 	public static ElasticsearchClient createImperative(RestClient restClient) {
 		return createImperative(restClient, null, DEFAULT_JSONP_MAPPER);
 	}
 
+	/**
+	 * Creates a new imperative {@link ElasticsearchClient}
+	 *
+	 * @param rest5Client the Rest5Client to use
+	 * @return the {@link ElasticsearchClient}
+	 */
+	public static ElasticsearchClient createImperative(Rest5Client rest5Client) {
+		return createImperative(rest5Client, null, DEFAULT_JSONP_MAPPER);
+	}
+
 	/**
 	 * Creates a new imperative {@link ElasticsearchClient}
 	 *
@@ -194,7 +233,9 @@ public final class ElasticsearchClients {
 	 * @param transportOptions options to be added to each request.
 	 * @param jsonpMapper the mapper for the transport to use
 	 * @return the {@link ElasticsearchClient}
+	 * @deprecated since 6.0, use the version with a Rest5Client.
 	 */
+	@Deprecated(since = "6.0", forRemoval = true)
 	public static ElasticsearchClient createImperative(RestClient restClient, @Nullable TransportOptions transportOptions,
 			JsonpMapper jsonpMapper) {
 
@@ -206,6 +247,27 @@ public final class ElasticsearchClients {
 		return createImperative(transport);
 	}
 
+	/**
+	 * Creates a new imperative {@link ElasticsearchClient}
+	 *
+	 * @param rest5Client the Rest5Client to use
+	 * @param transportOptions options to be added to each request.
+	 * @param jsonpMapper the mapper for the transport to use
+	 * @return the {@link ElasticsearchClient}
+	 * @since 6.0
+	 */
+	public static ElasticsearchClient createImperative(Rest5Client rest5Client,
+			@Nullable TransportOptions transportOptions,
+			JsonpMapper jsonpMapper) {
+
+		Assert.notNull(rest5Client, "restClient must not be null");
+
+		ElasticsearchTransport transport = getElasticsearchTransport(rest5Client, IMPERATIVE_CLIENT, transportOptions,
+				jsonpMapper);
+
+		return createImperative(transport);
+	}
+
 	/**
 	 * Creates a new {@link ElasticsearchClient} that uses the given {@link ElasticsearchTransport}.
 	 *
@@ -220,96 +282,6 @@ public final class ElasticsearchClients {
 	}
 	// endregion
 
-	// region low level RestClient
-	private static RestClientOptions.Builder getRestClientOptionsBuilder(@Nullable TransportOptions transportOptions) {
-
-		if (transportOptions instanceof RestClientOptions restClientOptions) {
-			return restClientOptions.toBuilder();
-		}
-
-		var builder = new RestClientOptions.Builder(RequestOptions.DEFAULT.toBuilder());
-
-		if (transportOptions != null) {
-			transportOptions.headers().forEach(header -> builder.addHeader(header.getKey(), header.getValue()));
-			transportOptions.queryParameters().forEach(builder::setParameter);
-			builder.onWarnings(transportOptions.onWarnings());
-		}
-
-		return builder;
-	}
-
-	/**
-	 * Creates a low level {@link RestClient} for the given configuration.
-	 *
-	 * @param clientConfiguration must not be {@literal null}
-	 * @return the {@link RestClient}
-	 */
-	public static RestClient getRestClient(ClientConfiguration clientConfiguration) {
-		return getRestClientBuilder(clientConfiguration).build();
-	}
-
-	private static RestClientBuilder getRestClientBuilder(ClientConfiguration clientConfiguration) {
-		HttpHost[] httpHosts = formattedHosts(clientConfiguration.getEndpoints(), clientConfiguration.useSsl()).stream()
-				.map(HttpHost::create).toArray(HttpHost[]::new);
-		RestClientBuilder builder = RestClient.builder(httpHosts);
-
-		if (clientConfiguration.getPathPrefix() != null) {
-			builder.setPathPrefix(clientConfiguration.getPathPrefix());
-		}
-
-		HttpHeaders headers = clientConfiguration.getDefaultHeaders();
-
-		if (!headers.isEmpty()) {
-			builder.setDefaultHeaders(toHeaderArray(headers));
-		}
-
-		builder.setHttpClientConfigCallback(clientBuilder -> {
-			if (clientConfiguration.getCaFingerprint().isPresent()) {
-				clientBuilder
-						.setSSLContext(TransportUtils.sslContextFromCaFingerprint(clientConfiguration.getCaFingerprint().get()));
-			}
-			clientConfiguration.getSslContext().ifPresent(clientBuilder::setSSLContext);
-			clientConfiguration.getHostNameVerifier().ifPresent(clientBuilder::setSSLHostnameVerifier);
-			clientBuilder.addInterceptorLast(new CustomHeaderInjector(clientConfiguration.getHeadersSupplier()));
-
-			RequestConfig.Builder requestConfigBuilder = RequestConfig.custom();
-			Duration connectTimeout = clientConfiguration.getConnectTimeout();
-
-			if (!connectTimeout.isNegative()) {
-				requestConfigBuilder.setConnectTimeout(Math.toIntExact(connectTimeout.toMillis()));
-			}
-
-			Duration socketTimeout = clientConfiguration.getSocketTimeout();
-
-			if (!socketTimeout.isNegative()) {
-				requestConfigBuilder.setSocketTimeout(Math.toIntExact(socketTimeout.toMillis()));
-				requestConfigBuilder.setConnectionRequestTimeout(Math.toIntExact(socketTimeout.toMillis()));
-			}
-
-			clientBuilder.setDefaultRequestConfig(requestConfigBuilder.build());
-
-			clientConfiguration.getProxy().map(HttpHost::create).ifPresent(clientBuilder::setProxy);
-
-			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
-					.getClientConfigurers()) {
-				if (clientConfigurer instanceof ElasticsearchHttpClientConfigurationCallback restClientConfigurationCallback) {
-					clientBuilder = restClientConfigurationCallback.configure(clientBuilder);
-				}
-			}
-
-			return clientBuilder;
-		});
-
-		for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurationCallback : clientConfiguration
-				.getClientConfigurers()) {
-			if (clientConfigurationCallback instanceof ElasticsearchRestClientConfigurationCallback configurationCallback) {
-				builder = configurationCallback.configure(builder);
-			}
-		}
-		return builder;
-	}
-	// endregion
-
 	// region Elasticsearch transport
 	/**
 	 * Creates an {@link ElasticsearchTransport} that will use the given client that additionally is customized with a
@@ -320,7 +292,9 @@ public final class ElasticsearchClients {
 	 * @param transportOptions options for the transport
 	 * @param jsonpMapper mapper for the transport
 	 * @return ElasticsearchTransport
+	 * @deprecated since 6.0, use the version taking a Rest5Client
 	 */
+	@Deprecated(since = "6.0", forRemoval = true)
 	public static ElasticsearchTransport getElasticsearchTransport(RestClient restClient, String clientType,
 			@Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
 
@@ -329,7 +303,7 @@ public final class ElasticsearchClients {
 		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
 
 		TransportOptions.Builder transportOptionsBuilder = transportOptions != null ? transportOptions.toBuilder()
-				: new RestClientOptions(RequestOptions.DEFAULT, false).toBuilder();
+				: new RestClientOptions(org.elasticsearch.client.RequestOptions.DEFAULT, false).toBuilder();
 
 		RestClientOptions.Builder restClientOptionsBuilder = getRestClientOptionsBuilder(transportOptions);
 
@@ -353,70 +327,35 @@ public final class ElasticsearchClients {
 
 		return new RestClientTransport(restClient, jsonpMapper, restClientOptionsBuilder.build());
 	}
+
+	/**
+	 * Creates an {@link ElasticsearchTransport} that will use the given client that additionally is customized with a
+	 * header to contain the clientType
+	 *
+	 * @param rest5Client the client to use
+	 * @param clientType the client type to pass in each request as header
+	 * @param transportOptions options for the transport
+	 * @param jsonpMapper mapper for the transport
+	 * @return ElasticsearchTransport
+	 */
+	public static ElasticsearchTransport getElasticsearchTransport(Rest5Client rest5Client, String clientType,
+			@Nullable TransportOptions transportOptions, JsonpMapper jsonpMapper) {
+
+		Assert.notNull(rest5Client, "restClient must not be null");
+		Assert.notNull(clientType, "clientType must not be null");
+		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
+
+		TransportOptions.Builder transportOptionsBuilder = transportOptions != null ? transportOptions.toBuilder()
+				: new Rest5ClientOptions(RequestOptions.DEFAULT, false).toBuilder();
+
+		Rest5ClientOptions.Builder rest5ClientOptionsBuilder = getRest5ClientOptionsBuilder(transportOptions);
+
+		rest5ClientOptionsBuilder.addHeader(X_SPRING_DATA_ELASTICSEARCH_CLIENT,
+				VersionInfo.clientVersions() + " / " + clientType);
+
+		return new Rest5ClientTransport(rest5Client, jsonpMapper, rest5ClientOptionsBuilder.build());
+	}
 	// endregion
 
-	private static List<String> formattedHosts(List<InetSocketAddress> hosts, boolean useSsl) {
-		return hosts.stream().map(it -> (useSsl ? "https" : "http") + "://" + it.getHostString() + ':' + it.getPort())
-				.collect(Collectors.toList());
-	}
-
-	private static org.apache.http.Header[] toHeaderArray(HttpHeaders headers) {
-		return headers.entrySet().stream() //
-				.flatMap(entry -> entry.getValue().stream() //
-						.map(value -> new BasicHeader(entry.getKey(), value))) //
-				.toArray(org.apache.http.Header[]::new);
-	}
-
-	/**
-	 * Interceptor to inject custom supplied headers.
-	 *
-	 * @since 4.4
-	 */
-	private record CustomHeaderInjector(Supplier<HttpHeaders> headersSupplier) implements HttpRequestInterceptor {
-
-		@Override
-		public void process(HttpRequest request, HttpContext context) {
-			HttpHeaders httpHeaders = headersSupplier.get();
-
-			if (httpHeaders != null && !httpHeaders.isEmpty()) {
-				Arrays.stream(toHeaderArray(httpHeaders)).forEach(request::addHeader);
-			}
-		}
-	}
-
-	/**
-	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
-	 * the Elasticsearch RestClient's Http client with a {@link HttpAsyncClientBuilder}
-	 *
-	 * @since 4.4
-	 */
-	public interface ElasticsearchHttpClientConfigurationCallback
-			extends ClientConfiguration.ClientConfigurationCallback<HttpAsyncClientBuilder> {
-
-		static ElasticsearchHttpClientConfigurationCallback from(
-				Function<HttpAsyncClientBuilder, HttpAsyncClientBuilder> httpClientBuilderCallback) {
-
-			Assert.notNull(httpClientBuilderCallback, "httpClientBuilderCallback must not be null");
-
-			return httpClientBuilderCallback::apply;
-		}
-	}
-
-	/**
-	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
-	 * the RestClient client with a {@link RestClientBuilder}
-	 *
-	 * @since 5.0
-	 */
-	public interface ElasticsearchRestClientConfigurationCallback
-			extends ClientConfiguration.ClientConfigurationCallback<RestClientBuilder> {
-
-		static ElasticsearchRestClientConfigurationCallback from(
-				Function<RestClientBuilder, RestClientBuilder> restClientBuilderCallback) {
-
-			Assert.notNull(restClientBuilderCallback, "restClientBuilderCallback must not be null");
-
-			return restClientBuilderCallback::apply;
-		}
-	}
+	// todo #3117 remove and document that ElasticsearchHttpClientConfigurationCallback has been move to RestClients.
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchConfiguration.java

@@ -17,28 +17,29 @@ package org.springframework.data.elasticsearch.client.elc;
 
 import co.elastic.clients.elasticsearch.ElasticsearchClient;
 import co.elastic.clients.json.JsonpMapper;
-import co.elastic.clients.json.jackson.JacksonJsonpMapper;
+import co.elastic.clients.json.jackson.Jackson3JsonpMapper;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.TransportOptions;
-import co.elastic.clients.transport.rest_client.RestClientOptions;
+import co.elastic.clients.transport.rest5_client.Rest5ClientOptions;
+import co.elastic.clients.transport.rest5_client.low_level.RequestOptions;
+import co.elastic.clients.transport.rest5_client.low_level.Rest5Client;
+import tools.jackson.databind.cfg.JsonNodeFeature;
+import tools.jackson.databind.json.JsonMapper;
 
-import org.elasticsearch.client.RequestOptions;
-import org.elasticsearch.client.RestClient;
 import org.springframework.context.annotation.Bean;
 import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.client.elc.rest5_client.Rest5Clients;
 import org.springframework.data.elasticsearch.config.ElasticsearchConfigurationSupport;
 import org.springframework.data.elasticsearch.core.ElasticsearchOperations;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.util.Assert;
 
-import com.fasterxml.jackson.annotation.JsonInclude;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.SerializationFeature;
-
 /**
  * Base class for a @{@link org.springframework.context.annotation.Configuration} class to set up the Elasticsearch
  * connection using the Elasticsearch Client. This class exposes different parts of the setup as Spring beans. Deriving
- * classes must provide the {@link ClientConfiguration} to use.
+ * classes must provide the {@link ClientConfiguration} to use. From Version 6.0 on, this class uses the new Rest5Client
+ * from Elasticsearch 9. The old implementation using the RestClient is still available under the name
+ * {@link ElasticsearchLegacyRestClientConfiguration}.
  *
  * @author Peter-Josef Meisch
  * @since 4.4
@@ -60,27 +61,27 @@ public abstract class ElasticsearchConfiguration extends ElasticsearchConfigurat
 	 * @return RestClient
 	 */
 	@Bean
-	public RestClient elasticsearchRestClient(ClientConfiguration clientConfiguration) {
+	public Rest5Client elasticsearchRest5Client(ClientConfiguration clientConfiguration) {
 
 		Assert.notNull(clientConfiguration, "clientConfiguration must not be null");
 
-		return ElasticsearchClients.getRestClient(clientConfiguration);
+		return Rest5Clients.getRest5Client(clientConfiguration);
 	}
 
 	/**
-	 * Provides the Elasticsearch transport to be used. The default implementation uses the {@link RestClient} bean and
+	 * Provides the Elasticsearch transport to be used. The default implementation uses the {@link Rest5Client} bean and
 	 * the {@link JsonpMapper} bean provided in this class.
 	 *
 	 * @return the {@link ElasticsearchTransport}
 	 * @since 5.2
 	 */
 	@Bean
-	public ElasticsearchTransport elasticsearchTransport(RestClient restClient, JsonpMapper jsonpMapper) {
+	public ElasticsearchTransport elasticsearchTransport(Rest5Client rest5Client, JsonpMapper jsonpMapper) {
 
-		Assert.notNull(restClient, "restClient must not be null");
+		Assert.notNull(rest5Client, "restClient must not be null");
 		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
 
-		return ElasticsearchClients.getElasticsearchTransport(restClient, ElasticsearchClients.IMPERATIVE_CLIENT,
+		return ElasticsearchClients.getElasticsearchTransport(rest5Client, ElasticsearchClients.IMPERATIVE_CLIENT,
 				transportOptions(), jsonpMapper);
 	}
 
@@ -115,7 +116,7 @@ public abstract class ElasticsearchConfiguration extends ElasticsearchConfigurat
 	}
 
 	/**
-	 * Provides the JsonpMapper bean that is used in the {@link #elasticsearchTransport(RestClient, JsonpMapper)} method.
+	 * Provides the JsonpMapper bean that is used in the {@link #elasticsearchTransport(Rest5Client, JsonpMapper)} method.
 	 *
 	 * @return the {@link JsonpMapper} to use
 	 * @since 5.2
@@ -125,16 +126,17 @@ public abstract class ElasticsearchConfiguration extends ElasticsearchConfigurat
 		// we need to create our own objectMapper that keeps null values in order to provide the storeNullValue
 		// functionality. The one Elasticsearch would provide removes the nulls. We remove unwanted nulls before they get
 		// into this mapper, so we can safely keep them here.
-		var objectMapper = (new ObjectMapper())
-				.configure(SerializationFeature.INDENT_OUTPUT, false)
-				.setSerializationInclusion(JsonInclude.Include.ALWAYS);
-		return new JacksonJsonpMapper(objectMapper);
+		JsonMapper jsonMapper = JsonMapper.builder()
+				.enable(JsonNodeFeature.WRITE_NULL_PROPERTIES)
+				.enable(JsonNodeFeature.READ_NULL_PROPERTIES)
+				.build();
+		return new Jackson3JsonpMapper(jsonMapper);
 	}
 
 	/**
 	 * @return the options that should be added to every request. Must not be {@literal null}
 	 */
 	public TransportOptions transportOptions() {
-		return new RestClientOptions(RequestOptions.DEFAULT, false);
+		return new Rest5ClientOptions(RequestOptions.DEFAULT, false);
 	}
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchExceptionTranslator.java

@@ -24,6 +24,7 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 import org.elasticsearch.client.ResponseException;
+import org.jspecify.annotations.Nullable;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.DataAccessResourceFailureException;
 import org.springframework.dao.DataIntegrityViolationException;
@@ -33,6 +34,7 @@ import org.springframework.data.elasticsearch.NoSuchIndexException;
 import org.springframework.data.elasticsearch.ResourceNotFoundException;
 import org.springframework.data.elasticsearch.UncategorizedElasticsearchException;
 import org.springframework.data.elasticsearch.VersionConflictException;
+import org.springframework.util.ClassUtils;
 
 /**
  * Simple {@link PersistenceExceptionTranslator} for Elasticsearch. Convert the given runtime exception to an
@@ -45,6 +47,9 @@ import org.springframework.data.elasticsearch.VersionConflictException;
  */
 public class ElasticsearchExceptionTranslator implements PersistenceExceptionTranslator {
 
+	public static final boolean LEGACY_RESTCLIENT_PRESENT = ClassUtils
+			.isPresent("org.elasticsearch.client.ResponseException", ElasticsearchExceptionTranslator.class.getClassLoader());
+
 	private final JsonpMapper jsonpMapper;
 
 	public ElasticsearchExceptionTranslator(JsonpMapper jsonpMapper) {
@@ -68,7 +73,7 @@ public class ElasticsearchExceptionTranslator implements PersistenceExceptionTra
 	}
 
 	@Override
-	public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
+	public @Nullable DataAccessException translateExceptionIfPossible(RuntimeException ex) {
 
 		checkForConflictException(ex);
 
@@ -118,15 +123,20 @@ public class ElasticsearchExceptionTranslator implements PersistenceExceptionTra
 		Integer status = null;
 		String message = null;
 
-		if (exception instanceof ResponseException responseException) {
+		if (LEGACY_RESTCLIENT_PRESENT && exception instanceof ResponseException responseException) {
+			// this code is for the old RestClient
 			status = responseException.getResponse().getStatusLine().getStatusCode();
 			message = responseException.getMessage();
+		} else if (exception instanceof ElasticsearchException elasticsearchException) {
+			// using the RestClient throws this
+			status = elasticsearchException.status();
+			message = elasticsearchException.getMessage();
 		} else if (exception.getCause() != null) {
 			checkForConflictException(exception.getCause());
 		}
 
 		if (status != null && message != null) {
-			if (status == 409 && message.contains("type\":\"version_conflict_engine_exception"))
+			if (status == 409 && message.contains("version_conflict_engine_exception"))
 				if (message.contains("version conflict, required seqNo")) {
 					throw new OptimisticLockingFailureException("Cannot index a document due to seq_no+primary_term conflict",
 							exception);

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchLegacyRestClientConfiguration.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2021-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import co.elastic.clients.elasticsearch.ElasticsearchClient;
+import co.elastic.clients.json.JsonpMapper;
+import co.elastic.clients.json.jackson.JacksonJsonpMapper;
+import co.elastic.clients.transport.ElasticsearchTransport;
+import co.elastic.clients.transport.TransportOptions;
+import co.elastic.clients.transport.rest_client.RestClientOptions;
+
+import org.elasticsearch.client.RequestOptions;
+import org.elasticsearch.client.RestClient;
+import org.springframework.context.annotation.Bean;
+import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.client.elc.rest_client.RestClients;
+import org.springframework.data.elasticsearch.config.ElasticsearchConfigurationSupport;
+import org.springframework.data.elasticsearch.core.ElasticsearchOperations;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
+import org.springframework.util.Assert;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+
+/**
+ * Base class for a @{@link org.springframework.context.annotation.Configuration} class to set up the Elasticsearch
+ * connection using the Elasticsearch Client. This class exposes different parts of the setup as Spring beans. Deriving
+ * classes must provide the {@link ClientConfiguration} to use. <br/>
+ * This class uses the Elasticsearch RestClient which was replaced by the Rest5Client in Elasticsearch 9. It is still
+ * available here but deprecated.
+ *
+ * @author Peter-Josef Meisch
+ * @since 4.4
+ * @deprecated since 6.0, use {@link ElasticsearchConfiguration}
+ */
+@Deprecated(since = "6.0", forRemoval = true)
+public abstract class ElasticsearchLegacyRestClientConfiguration extends ElasticsearchConfigurationSupport {
+
+	/**
+	 * Must be implemented by deriving classes to provide the {@link ClientConfiguration}.
+	 *
+	 * @return configuration, must not be {@literal null}
+	 */
+	@Bean(name = "elasticsearchClientConfiguration")
+	public abstract ClientConfiguration clientConfiguration();
+
+	/**
+	 * Provides the underlying low level Elasticsearch RestClient.
+	 *
+	 * @param clientConfiguration configuration for the client, must not be {@literal null}
+	 * @return RestClient
+	 */
+	@Bean
+	public RestClient elasticsearchRestClient(ClientConfiguration clientConfiguration) {
+
+		Assert.notNull(clientConfiguration, "clientConfiguration must not be null");
+
+		return RestClients.getRestClient(clientConfiguration);
+	}
+
+	/**
+	 * Provides the Elasticsearch transport to be used. The default implementation uses the {@link RestClient} bean and
+	 * the {@link JsonpMapper} bean provided in this class.
+	 *
+	 * @return the {@link ElasticsearchTransport}
+	 * @since 5.2
+	 */
+	@Bean
+	public ElasticsearchTransport elasticsearchTransport(RestClient restClient, JsonpMapper jsonpMapper) {
+
+		Assert.notNull(restClient, "restClient must not be null");
+		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
+
+		return ElasticsearchClients.getElasticsearchTransport(restClient, ElasticsearchClients.IMPERATIVE_CLIENT,
+				transportOptions(), jsonpMapper);
+	}
+
+	/**
+	 * Provides the {@link ElasticsearchClient} to be used.
+	 *
+	 * @param transport the {@link ElasticsearchTransport} to use
+	 * @return ElasticsearchClient instance
+	 */
+	@Bean
+	public ElasticsearchClient elasticsearchClient(ElasticsearchTransport transport) {
+
+		Assert.notNull(transport, "transport must not be null");
+
+		return ElasticsearchClients.createImperative(transport);
+	}
+
+	/**
+	 * Creates a {@link ElasticsearchOperations} implementation using an {@link ElasticsearchClient}.
+	 *
+	 * @return never {@literal null}.
+	 */
+	@Bean(name = { "elasticsearchOperations", "elasticsearchTemplate" })
+	public ElasticsearchOperations elasticsearchOperations(ElasticsearchConverter elasticsearchConverter,
+			ElasticsearchClient elasticsearchClient) {
+
+		ElasticsearchTemplate template = new ElasticsearchTemplate(elasticsearchClient, elasticsearchConverter);
+		template.setRefreshPolicy(refreshPolicy());
+
+		return template;
+	}
+
+	/**
+	 * Provides the JsonpMapper bean that is used in the {@link #elasticsearchTransport(RestClient, JsonpMapper)} method.
+	 *
+	 * @return the {@link JsonpMapper} to use
+	 * @since 5.2
+	 */
+	@Bean
+	public JsonpMapper jsonpMapper() {
+		// we need to create our own objectMapper that keeps null values in order to provide the storeNullValue
+		// functionality. The one Elasticsearch would provide removes the nulls. We remove unwanted nulls before they get
+		// into this mapper, so we can safely keep them here.
+		var objectMapper = (new ObjectMapper())
+				.configure(SerializationFeature.INDENT_OUTPUT, false)
+				.setSerializationInclusion(JsonInclude.Include.ALWAYS);
+		return new JacksonJsonpMapper(objectMapper);
+	}
+
+	/**
+	 * @return the options that should be added to every request. Must not be {@literal null}
+	 */
+	public TransportOptions transportOptions() {
+		return new RestClientOptions(RequestOptions.DEFAULT, false);
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchObservation.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import io.micrometer.common.docs.KeyName;
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationConvention;
+import io.micrometer.observation.docs.ObservationDocumentation;
+
+/**
+ * {@link ObservationDocumentation} for Spring Data Elasticsearch template operations.
+ *
+ * @author maryantocinn
+ * @since 6.1
+ */
+public enum ElasticsearchObservation implements ObservationDocumentation {
+
+	/**
+	 * Timer created around a Spring Data Elasticsearch template operation.
+	 */
+	ELASTICSEARCH_COMMAND_OBSERVATION {
+		@Override
+		public String getName() {
+			return "spring.data.elasticsearch.command";
+		}
+
+		@Override
+		public Class<? extends ObservationConvention<? extends Observation.Context>> getDefaultConvention() {
+			return DefaultElasticsearchObservationConvention.class;
+		}
+
+		@Override
+		public KeyName[] getLowCardinalityKeyNames() {
+			return LowCardinalityKeyNames.values();
+		}
+
+		@Override
+		public KeyName[] getHighCardinalityKeyNames() {
+			return HighCardinalityKeyNames.values();
+		}
+	};
+
+	/**
+	 * Low cardinality key names for Spring Data Elasticsearch observations. These become metric dimensions and MUST be
+	 * present on every observation to satisfy backends like Prometheus that require consistent tag key sets.
+	 */
+	enum LowCardinalityKeyNames implements KeyName {
+
+		/**
+		 * The Spring Data operation being performed (e.g., save, search, delete, bulk).
+		 */
+		OPERATION {
+			@Override
+			public String asString() {
+				return "spring.data.operation";
+			}
+		},
+
+		/**
+		 * The target collection (index) name. Only present when the operation targets a specific index.
+		 */
+		COLLECTION {
+			@Override
+			public String asString() {
+				return "spring.data.collection";
+			}
+		}
+	}
+
+	/**
+	 * High cardinality key names for Spring Data Elasticsearch observations. These appear only on traces/spans, not on
+	 * metrics, because their values are unbounded or optional per operation.
+	 */
+	enum HighCardinalityKeyNames implements KeyName {
+
+		/**
+		 * The number of operations included in a batch (bulk) request. Only present for bulk operations.
+		 */
+		BATCH_SIZE {
+			@Override
+			public String asString() {
+				return "spring.data.batch.size";
+			}
+		}
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchObservationContext.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import io.micrometer.observation.Observation;
+
+import org.jspecify.annotations.Nullable;
+import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
+
+/**
+ * {@link Observation.Context} for Spring Data Elasticsearch operations. One instance is created per observed operation.
+ * It carries contextual data that conventions use to produce observation names and key-values.
+ *
+ * @author maryantocinn
+ * @since 6.1
+ */
+public class ElasticsearchObservationContext extends Observation.Context {
+
+	private final ElasticsearchOperationName operationName;
+	@Nullable private final IndexCoordinates indexCoordinates;
+	@Nullable private Integer batchSize;
+
+	public ElasticsearchObservationContext(ElasticsearchOperationName operationName,
+			@Nullable IndexCoordinates indexCoordinates) {
+		this.operationName = operationName;
+		this.indexCoordinates = indexCoordinates;
+	}
+
+	/**
+	 * @return the Spring Data operation being performed.
+	 */
+	public ElasticsearchOperationName getOperationName() {
+		return operationName;
+	}
+
+	/**
+	 * @return the target index coordinates, or {@literal null} if the operation is not index-specific.
+	 */
+	@Nullable
+	public IndexCoordinates getIndexCoordinates() {
+		return indexCoordinates;
+	}
+
+	/**
+	 * @return the comma-joined index name(s), or {@literal null} if no index coordinates are set.
+	 */
+	@Nullable
+	public String getIndexName() {
+		return indexCoordinates != null ? String.join(",", indexCoordinates.getIndexNames()) : null;
+	}
+
+	/**
+	 * @return the batch size, or {@literal null} if not a batch operation.
+	 */
+	@Nullable
+	public Integer getBatchSize() {
+		return batchSize;
+	}
+
+	/**
+	 * Set the number of operations included in a batch (bulk) request.
+	 *
+	 * @param batchSize the batch size, can be {@literal null}
+	 */
+	public void setBatchSize(@Nullable Integer batchSize) {
+		this.batchSize = batchSize;
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchObservationConvention.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationConvention;
+
+/**
+ * {@link ObservationConvention} for Spring Data Elasticsearch operations. Implement this interface and register it as a
+ * bean to customize observation names and key-values.
+ *
+ * @author maryantocinn
+ * @since 6.1
+ */
+public interface ElasticsearchObservationConvention extends ObservationConvention<ElasticsearchObservationContext> {
+
+	@Override
+	default boolean supportsContext(Observation.Context context) {
+		return context instanceof ElasticsearchObservationContext;
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchOperationName.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2026-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+/**
+ * Enumeration of Spring Data Elasticsearch operation names used in observations.
+ *
+ * @author maryantocinn
+ * @since 6.1
+ */
+public enum ElasticsearchOperationName {
+
+	SAVE("save"), //
+	INDEX("index"), //
+	GET("get"), //
+	MULTI_GET("multiGet"), //
+	EXISTS("exists"), //
+	DELETE("delete"), //
+	DELETE_BY_QUERY("deleteByQuery"), //
+	BULK("bulk"), //
+	UPDATE("update"), //
+	UPDATE_BY_QUERY("updateByQuery"), //
+	COUNT("count"), //
+	SEARCH("search");
+
+	private final String value;
+
+	ElasticsearchOperationName(String value) {
+		this.value = value;
+	}
+
+	/**
+	 * @return the operation name as a string value used in observation key values.
+	 */
+	public String getValue() {
+		return value;
+	}
+
+	@Override
+	public String toString() {
+		return value;
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ElasticsearchTemplate.java

@@ -17,29 +17,11 @@ package org.springframework.data.elasticsearch.client.elc;
 
 import static org.springframework.data.elasticsearch.client.elc.TypeUtils.*;
 
-import co.elastic.clients.elasticsearch.ElasticsearchClient;
-import co.elastic.clients.elasticsearch._types.Time;
-import co.elastic.clients.elasticsearch.core.*;
-import co.elastic.clients.elasticsearch.core.bulk.BulkResponseItem;
-import co.elastic.clients.elasticsearch.core.msearch.MultiSearchResponseItem;
-import co.elastic.clients.elasticsearch.core.search.ResponseBody;
-import co.elastic.clients.elasticsearch.sql.ElasticsearchSqlClient;
-import co.elastic.clients.elasticsearch.sql.QueryResponse;
-import co.elastic.clients.json.JsonpMapper;
-import co.elastic.clients.transport.Version;
-
-import java.io.IOException;
-import java.time.Duration;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-import java.util.stream.Collectors;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
+import org.springframework.beans.BeansException;
+import org.springframework.context.ApplicationContext;
 import org.springframework.data.elasticsearch.BulkFailureException;
 import org.springframework.data.elasticsearch.client.UnsupportedBackendOperation;
 import org.springframework.data.elasticsearch.core.AbstractElasticsearchTemplate;
@@ -59,9 +41,32 @@ import org.springframework.data.elasticsearch.core.reindex.ReindexRequest;
 import org.springframework.data.elasticsearch.core.reindex.ReindexResponse;
 import org.springframework.data.elasticsearch.core.script.Script;
 import org.springframework.data.elasticsearch.core.sql.SqlResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import java.io.IOException;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+
+import co.elastic.clients.elasticsearch.ElasticsearchClient;
+import co.elastic.clients.elasticsearch._types.Time;
+import co.elastic.clients.elasticsearch.core.*;
+import co.elastic.clients.elasticsearch.core.bulk.BulkResponseItem;
+import co.elastic.clients.elasticsearch.core.msearch.MultiSearchResponseItem;
+import co.elastic.clients.elasticsearch.core.search.ResponseBody;
+import co.elastic.clients.elasticsearch.sql.ElasticsearchSqlClient;
+import co.elastic.clients.elasticsearch.sql.QueryResponse;
+import co.elastic.clients.json.JsonpMapper;
+import co.elastic.clients.transport.Version;
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationRegistry;
+
 /**
  * Implementation of {@link org.springframework.data.elasticsearch.core.ElasticsearchOperations} using the new
  * Elasticsearch client.
@@ -70,12 +75,15 @@ import org.springframework.util.Assert;
  * @author Hamid Rahimi
  * @author Illia Ulianov
  * @author Haibo Liu
+ * @author maryantocinn
  * @since 4.4
  */
 public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 
 	private static final Log LOGGER = LogFactory.getLog(ElasticsearchTemplate.class);
 
+	@Nullable private ElasticsearchObservationConvention observationConvention;
+
 	private final ElasticsearchClient client;
 	private final ElasticsearchSqlClient sqlClient;
 	private final RequestConverter requestConverter;
@@ -113,6 +121,61 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 	protected AbstractElasticsearchTemplate doCopy() {
 		return new ElasticsearchTemplate(client, elasticsearchConverter);
 	}
+
+	@Override
+	protected void customizeCopy(AbstractElasticsearchTemplate copy) {
+
+		if (copy instanceof ElasticsearchTemplate elasticsearchTemplate) {
+			elasticsearchTemplate.observationConvention = this.observationConvention;
+		}
+	}
+
+	@Override
+	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
+
+		super.setApplicationContext(applicationContext);
+
+		if (observationRegistry == ObservationRegistry.NOOP) {
+			applicationContext.getBeanProvider(ObservationRegistry.class).ifAvailable(this::setObservationRegistry);
+		}
+
+		if (observationConvention == null) {
+			applicationContext.getBeanProvider(ElasticsearchObservationConvention.class)
+					.ifAvailable(this::setObservationConvention);
+		}
+	}
+
+	/**
+	 * Set a custom {@link ElasticsearchObservationConvention} to override the default convention.
+	 *
+	 * @param observationConvention can be {@literal null}.
+	 * @since 6.1
+	 */
+	public void setObservationConvention(@Nullable ElasticsearchObservationConvention observationConvention) {
+		this.observationConvention = observationConvention;
+	}
+
+	private <T> T observe(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			Supplier<T> action) {
+		Observation observation = createObservation(operationName, index, null);
+		return observation.observe(action);
+	}
+
+	private <T> T observe(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index, int batchSize,
+			Supplier<T> action) {
+		Observation observation = createObservation(operationName, index, batchSize);
+		return observation.observe(action);
+	}
+
+	private Observation createObservation(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			@Nullable Integer batchSize) {
+
+		ElasticsearchObservationContext context = new ElasticsearchObservationContext(operationName, index);
+		context.setBatchSize(batchSize);
+
+		return ElasticsearchObservation.ELASTICSEARCH_COMMAND_OBSERVATION.observation(observationConvention,
+				DefaultElasticsearchObservationConvention.INSTANCE, () -> context, observationRegistry);
+	}
 	// endregion
 
 	// region child templates
@@ -137,16 +200,45 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 	// endregion
 
 	// region document operations
+	@Override
+	public <T> T save(T entity, IndexCoordinates index) {
+		return observe(ElasticsearchOperationName.SAVE, index, () -> super.save(entity, index));
+	}
+
+	@Override
+	public String index(IndexQuery query, IndexCoordinates index) {
+		return observe(ElasticsearchOperationName.INDEX, index, () -> super.index(query, index));
+	}
+
+	@Override
+	public boolean exists(String id, IndexCoordinates index) {
+		return observe(ElasticsearchOperationName.EXISTS, index, () -> super.exists(id, index));
+	}
+
+	@Override
+	public String delete(String id, IndexCoordinates index) {
+		return observe(ElasticsearchOperationName.DELETE, index, () -> super.delete(id, index));
+	}
+
+	@Override
+	public List<IndexedObjectInformation> bulkOperation(List<?> queries, BulkOptions bulkOptions,
+			IndexCoordinates index) {
+		return observe(ElasticsearchOperationName.BULK, index, queries.size(),
+				() -> super.bulkOperation(queries, bulkOptions, index));
+	}
+
 	@Override
 	@Nullable
 	public <T> T get(String id, Class<T> clazz, IndexCoordinates index) {
 
-		GetRequest getRequest = requestConverter.documentGetRequest(elasticsearchConverter.convertId(id),
-				routingResolver.getRouting(), index);
-		GetResponse<EntityAsMap> getResponse = execute(client -> client.get(getRequest, EntityAsMap.class));
+		return observe(ElasticsearchOperationName.GET, index, () -> {
+			GetRequest getRequest = requestConverter.documentGetRequest(elasticsearchConverter.convertId(id),
+					routingResolver.getRouting(), index);
+			GetResponse<EntityAsMap> getResponse = execute(client -> client.get(getRequest, EntityAsMap.class));
 
-		ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(elasticsearchConverter, clazz, index);
-		return callback.doWith(DocumentAdapters.from(getResponse));
+			ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(elasticsearchConverter, clazz, index);
+			return callback.doWith(DocumentAdapters.from(getResponse));
+		});
 	}
 
 	@Override
@@ -155,15 +247,17 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 		Assert.notNull(query, "query must not be null");
 		Assert.notNull(clazz, "clazz must not be null");
 
-		MgetRequest request = requestConverter.documentMgetRequest(query, clazz, index);
-		MgetResponse<EntityAsMap> result = execute(client -> client.mget(request, EntityAsMap.class));
+		return observe(ElasticsearchOperationName.MULTI_GET, index, () -> {
+			MgetRequest request = requestConverter.documentMgetRequest(query, clazz, index);
+			MgetResponse<EntityAsMap> result = execute(client -> client.mget(request, EntityAsMap.class));
 
-		ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(elasticsearchConverter, clazz, index);
+			ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(elasticsearchConverter, clazz, index);
 
-		return DocumentAdapters.from(result).stream() //
-				.map(multiGetItem -> MultiGetItem.of( //
-						multiGetItem.isFailed() ? null : callback.doWith(multiGetItem.getItem()), multiGetItem.getFailure())) //
-				.collect(Collectors.toList());
+			return DocumentAdapters.from(result).stream() //
+					.map(multiGetItem -> MultiGetItem.of( //
+							multiGetItem.isFailed() ? null : callback.doWith(multiGetItem.getItem()), multiGetItem.getFailure())) //
+					.collect(Collectors.toList());
+		});
 	}
 
 	@Override
@@ -185,22 +279,26 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 	public ByQueryResponse delete(DeleteQuery query, Class<?> clazz, IndexCoordinates index) {
 		Assert.notNull(query, "query must not be null");
 
-		DeleteByQueryRequest request = requestConverter.documentDeleteByQueryRequest(query, routingResolver.getRouting(),
-				clazz, index, getRefreshPolicy());
+		return observe(ElasticsearchOperationName.DELETE_BY_QUERY, index, () -> {
+			DeleteByQueryRequest request = requestConverter.documentDeleteByQueryRequest(query, routingResolver.getRouting(),
+					clazz, index, getRefreshPolicy());
 
-		DeleteByQueryResponse response = execute(client -> client.deleteByQuery(request));
+			DeleteByQueryResponse response = execute(client -> client.deleteByQuery(request));
 
-		return responseConverter.byQueryResponse(response);
+			return responseConverter.byQueryResponse(response);
+		});
 	}
 
 	@Override
 	public UpdateResponse update(UpdateQuery updateQuery, IndexCoordinates index) {
 
-		UpdateRequest<Document, ?> request = requestConverter.documentUpdateRequest(updateQuery, index, getRefreshPolicy(),
-				routingResolver.getRouting());
-		co.elastic.clients.elasticsearch.core.UpdateResponse<Document> response = execute(
-				client -> client.update(request, Document.class));
-		return UpdateResponse.of(result(response.result()));
+		return observe(ElasticsearchOperationName.UPDATE, index, () -> {
+			UpdateRequest<Document, ?> request = requestConverter.documentUpdateRequest(updateQuery, index,
+					getRefreshPolicy(), routingResolver.getRouting());
+			co.elastic.clients.elasticsearch.core.UpdateResponse<Document> response = execute(
+					client -> client.update(request, Document.class));
+			return UpdateResponse.of(result(response.result()));
+		});
 	}
 
 	@Override
@@ -209,11 +307,13 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 		Assert.notNull(updateQuery, "updateQuery must not be null");
 		Assert.notNull(index, "index must not be null");
 
-		UpdateByQueryRequest request = requestConverter.documentUpdateByQueryRequest(updateQuery, index,
-				getRefreshPolicy());
+		return observe(ElasticsearchOperationName.UPDATE_BY_QUERY, index, () -> {
+			UpdateByQueryRequest request = requestConverter.documentUpdateByQueryRequest(updateQuery, index,
+					getRefreshPolicy());
 
-		UpdateByQueryResponse byQueryResponse = execute(client -> client.updateByQuery(request));
-		return responseConverter.byQueryResponse(byQueryResponse);
+			UpdateByQueryResponse byQueryResponse = execute(client -> client.updateByQuery(request));
+			return responseConverter.byQueryResponse(byQueryResponse);
+		});
 	}
 
 	@Override
@@ -328,12 +428,14 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 		Assert.notNull(query, "query must not be null");
 		Assert.notNull(index, "index must not be null");
 
-		SearchRequest searchRequest = requestConverter.searchRequest(query, routingResolver.getRouting(), clazz, index,
-				true);
+		return observe(ElasticsearchOperationName.COUNT, index, () -> {
+			SearchRequest searchRequest = requestConverter.searchRequest(query, routingResolver.getRouting(), clazz, index,
+					true);
 
-		SearchResponse<EntityAsMap> searchResponse = execute(client -> client.search(searchRequest, EntityAsMap.class));
+			SearchResponse<EntityAsMap> searchResponse = execute(client -> client.search(searchRequest, EntityAsMap.class));
 
-		return searchResponse.hits().total().value();
+			return searchResponse.hits().total().value();
+		});
 	}
 
 	@Override
@@ -343,11 +445,13 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 		Assert.notNull(clazz, "clazz must not be null");
 		Assert.notNull(index, "index must not be null");
 
-		if (query instanceof SearchTemplateQuery searchTemplateQuery) {
-			return doSearch(searchTemplateQuery, clazz, index);
-		} else {
-			return doSearch(query, clazz, index);
-		}
+		return observe(ElasticsearchOperationName.SEARCH, index, () -> {
+			if (query instanceof SearchTemplateQuery searchTemplateQuery) {
+				return doSearch(searchTemplateQuery, clazz, index);
+			} else {
+				return doSearch(query, clazz, index);
+			}
+		});
 	}
 
 	protected <T> SearchHits<T> doSearch(Query query, Class<T> clazz, IndexCoordinates index) {
@@ -658,7 +762,7 @@ public class ElasticsearchTemplate extends AbstractElasticsearchTemplate {
 			QueryResponse response = sqlClient.query(requestConverter.sqlQueryRequest(query));
 
 			return responseConverter.sqlResponse(response);
-		} catch (IOException e) {
+		} catch (Exception e) {
 			throw exceptionTranslator.translateException(e);
 		}
 	}

src/main/java/org/springframework/data/elasticsearch/client/elc/HighlightQueryBuilder.java

@@ -17,9 +17,12 @@ package org.springframework.data.elasticsearch.client.elc;
 
 import static org.springframework.data.elasticsearch.client.elc.TypeUtils.*;
 
+import co.elastic.clients.util.NamedValue;
+
 import java.util.Arrays;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentProperty;
 import org.springframework.data.elasticsearch.core.query.highlight.Highlight;
@@ -27,7 +30,6 @@ import org.springframework.data.elasticsearch.core.query.highlight.HighlightFiel
 import org.springframework.data.elasticsearch.core.query.highlight.HighlightFieldParameters;
 import org.springframework.data.elasticsearch.core.query.highlight.HighlightParameters;
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -43,7 +45,8 @@ class HighlightQueryBuilder {
 	private final RequestConverter requestConverter;
 
 	HighlightQueryBuilder(
-			MappingContext<? extends ElasticsearchPersistentEntity<?>, ElasticsearchPersistentProperty> mappingContext, RequestConverter requestConverter) {
+			MappingContext<? extends ElasticsearchPersistentEntity<?>, ElasticsearchPersistentProperty> mappingContext,
+			RequestConverter requestConverter) {
 		this.mappingContext = mappingContext;
 		this.requestConverter = requestConverter;
 	}
@@ -59,10 +62,11 @@ class HighlightQueryBuilder {
 
 		for (HighlightField highlightField : highlight.getFields()) {
 			String mappedName = mapFieldName(highlightField.getName(), type);
-			highlightBuilder.fields(mappedName, hf -> {
-				addParameters(highlightField.getParameters(), hf, type);
-				return hf;
-			});
+			highlightBuilder.fields(
+					NamedValue.of(mappedName, co.elastic.clients.elasticsearch.core.search.HighlightField.of(hf -> {
+						addParameters(highlightField.getParameters(), hf, type);
+						return hf;
+					})));
 		}
 
 		return highlightBuilder.build();

src/main/java/org/springframework/data/elasticsearch/client/elc/IndicesTemplate.java

@@ -27,8 +27,10 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
+import org.springframework.data.elasticsearch.ResourceNotFoundException;
 import org.springframework.data.elasticsearch.UncategorizedElasticsearchException;
 import org.springframework.data.elasticsearch.annotations.Mapping;
 import org.springframework.data.elasticsearch.core.IndexInformation;
@@ -49,7 +51,6 @@ import org.springframework.data.elasticsearch.core.mapping.Alias;
 import org.springframework.data.elasticsearch.core.mapping.CreateIndexSettings;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -315,15 +316,20 @@ public class IndicesTemplate extends ChildTemplate<ElasticsearchTransport, Elast
 	}
 
 	@Override
-	public TemplateData getTemplate(GetTemplateRequest getTemplateRequest) {
+	public @Nullable TemplateData getTemplate(GetTemplateRequest getTemplateRequest) {
 
 		Assert.notNull(getTemplateRequest, "getTemplateRequest must not be null");
 
 		co.elastic.clients.elasticsearch.indices.GetTemplateRequest getTemplateRequestES = requestConverter
 				.indicesGetTemplateRequest(getTemplateRequest);
-		GetTemplateResponse getTemplateResponse = execute(client -> client.getTemplate(getTemplateRequestES));
 
-		return responseConverter.indicesGetTemplateData(getTemplateResponse, getTemplateRequest.getTemplateName());
+		try {
+			GetTemplateResponse getTemplateResponse = execute(client -> client.getTemplate(getTemplateRequestES));
+			return responseConverter.indicesGetTemplateData(getTemplateResponse, getTemplateRequest.getTemplateName());
+		} catch (ResourceNotFoundException e) {
+			// since Elasticsearch 9.1.0 we get an exception (404) instead of an empty result
+			return null;
+		}
 	}
 
 	@Override

src/main/java/org/springframework/data/elasticsearch/client/elc/JsonUtils.java

@@ -23,7 +23,7 @@ import java.nio.charset.StandardCharsets;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * @author Peter-Josef Meisch
@@ -48,7 +48,7 @@ final class JsonUtils {
 	}
 
 	@Nullable
-	public static String queryToJson(@Nullable co.elastic.clients.elasticsearch._types.query_dsl.Query query,
+	public static String queryToJson(co.elastic.clients.elasticsearch._types.query_dsl.@Nullable Query query,
 			JsonpMapper mapper) {
 
 		if (query == null) {

src/main/java/org/springframework/data/elasticsearch/client/elc/NativeQuery.java

@@ -28,8 +28,8 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.query.BaseQuery;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -44,7 +44,7 @@ import org.springframework.util.Assert;
 public class NativeQuery extends BaseQuery {
 
 	@Nullable private final Query query;
-	@Nullable private org.springframework.data.elasticsearch.core.query.Query springDataQuery;
+	private org.springframework.data.elasticsearch.core.query.@Nullable Query springDataQuery;
 	@Nullable private Query filter;
 	// note: the new client does not have pipeline aggs, these are just set up as normal aggs
 	private final Map<String, Aggregation> aggregations = new LinkedHashMap<>();
@@ -117,7 +117,7 @@ public class NativeQuery extends BaseQuery {
 	 * @see NativeQueryBuilder#withQuery(org.springframework.data.elasticsearch.core.query.Query).
 	 * @since 5.1
 	 */
-	public void setSpringDataQuery(@Nullable org.springframework.data.elasticsearch.core.query.Query springDataQuery) {
+	public void setSpringDataQuery(org.springframework.data.elasticsearch.core.query.@Nullable Query springDataQuery) {
 		this.springDataQuery = springDataQuery;
 	}
 
@@ -129,8 +129,7 @@ public class NativeQuery extends BaseQuery {
 		return knnSearches;
 	}
 
-	@Nullable
-	public org.springframework.data.elasticsearch.core.query.Query getSpringDataQuery() {
+	public org.springframework.data.elasticsearch.core.query.@Nullable Query getSpringDataQuery() {
 		return springDataQuery;
 	}
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/NativeQueryBuilder.java

@@ -33,8 +33,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.query.BaseQueryBuilder;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -53,7 +53,7 @@ public class NativeQueryBuilder extends BaseQueryBuilder<NativeQuery, NativeQuer
 	private final List<SortOptions> sortOptions = new ArrayList<>();
 	private final Map<String, JsonData> searchExtensions = new LinkedHashMap<>();
 
-	@Nullable private org.springframework.data.elasticsearch.core.query.Query springDataQuery;
+	private org.springframework.data.elasticsearch.core.query.@Nullable Query springDataQuery;
 	@Nullable private KnnQuery knnQuery;
 	@Nullable private List<KnnSearch> knnSearches = Collections.emptyList();
 
@@ -104,8 +104,7 @@ public class NativeQueryBuilder extends BaseQueryBuilder<NativeQuery, NativeQuer
 		return knnSearches;
 	}
 
-	@Nullable
-	public org.springframework.data.elasticsearch.core.query.Query getSpringDataQuery() {
+	public org.springframework.data.elasticsearch.core.query.@Nullable Query getSpringDataQuery() {
 		return springDataQuery;
 	}
 

src/main/java/org/springframework/data/elasticsearch/client/elc/Queries.java

@@ -34,9 +34,9 @@ import java.util.Base64;
 import java.util.List;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.geo.GeoPoint;
 import org.springframework.data.elasticsearch.core.query.BaseQueryBuilder;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchClient.java

@@ -30,7 +30,7 @@ import reactor.core.publisher.Mono;
 import java.io.IOException;
 import java.util.function.Function;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchClusterClient.java

@@ -16,7 +16,15 @@
 package org.springframework.data.elasticsearch.client.elc;
 
 import co.elastic.clients.ApiClient;
-import co.elastic.clients.elasticsearch.cluster.*;
+import co.elastic.clients.elasticsearch.cluster.DeleteComponentTemplateRequest;
+import co.elastic.clients.elasticsearch.cluster.DeleteComponentTemplateResponse;
+import co.elastic.clients.elasticsearch.cluster.ExistsComponentTemplateRequest;
+import co.elastic.clients.elasticsearch.cluster.GetComponentTemplateRequest;
+import co.elastic.clients.elasticsearch.cluster.GetComponentTemplateResponse;
+import co.elastic.clients.elasticsearch.cluster.HealthRequest;
+import co.elastic.clients.elasticsearch.cluster.HealthResponse;
+import co.elastic.clients.elasticsearch.cluster.PutComponentTemplateRequest;
+import co.elastic.clients.elasticsearch.cluster.PutComponentTemplateResponse;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.TransportOptions;
 import co.elastic.clients.transport.endpoints.BooleanResponse;
@@ -25,7 +33,7 @@ import reactor.core.publisher.Mono;
 
 import java.util.function.Function;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Reactive version of the {@link co.elastic.clients.elasticsearch.cluster.ElasticsearchClusterClient}

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchConfiguration.java

@@ -16,15 +16,19 @@
 package org.springframework.data.elasticsearch.client.elc;
 
 import co.elastic.clients.json.JsonpMapper;
-import co.elastic.clients.json.jackson.JacksonJsonpMapper;
+import co.elastic.clients.json.jackson.Jackson3JsonpMapper;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.TransportOptions;
-import co.elastic.clients.transport.rest_client.RestClientOptions;
+import co.elastic.clients.transport.rest5_client.Rest5ClientOptions;
+import co.elastic.clients.transport.rest5_client.low_level.RequestOptions;
+import co.elastic.clients.transport.rest5_client.low_level.Rest5Client;
+import tools.jackson.databind.cfg.JsonNodeFeature;
+import tools.jackson.databind.json.JsonMapper;
 
-import org.elasticsearch.client.RequestOptions;
 import org.elasticsearch.client.RestClient;
 import org.springframework.context.annotation.Bean;
 import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.client.elc.rest5_client.Rest5Clients;
 import org.springframework.data.elasticsearch.config.ElasticsearchConfigurationSupport;
 import org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
@@ -55,11 +59,11 @@ public abstract class ReactiveElasticsearchConfiguration extends ElasticsearchCo
 	 * @return RestClient
 	 */
 	@Bean
-	public RestClient elasticsearchRestClient(ClientConfiguration clientConfiguration) {
+	public Rest5Client elasticsearchRestClient(ClientConfiguration clientConfiguration) {
 
 		Assert.notNull(clientConfiguration, "clientConfiguration must not be null");
 
-		return ElasticsearchClients.getRestClient(clientConfiguration);
+		return Rest5Clients.getRest5Client(clientConfiguration);
 	}
 
 	/**
@@ -70,12 +74,12 @@ public abstract class ReactiveElasticsearchConfiguration extends ElasticsearchCo
 	 * @since 5.2
 	 */
 	@Bean
-	public ElasticsearchTransport elasticsearchTransport(RestClient restClient, JsonpMapper jsonpMapper) {
+	public ElasticsearchTransport elasticsearchTransport(Rest5Client rest5Client, JsonpMapper jsonpMapper) {
 
-		Assert.notNull(restClient, "restClient must not be null");
+		Assert.notNull(rest5Client, "restClient must not be null");
 		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
 
-		return ElasticsearchClients.getElasticsearchTransport(restClient, ElasticsearchClients.REACTIVE_CLIENT,
+		return ElasticsearchClients.getElasticsearchTransport(rest5Client, ElasticsearchClients.REACTIVE_CLIENT,
 				transportOptions(), jsonpMapper);
 	}
 
@@ -110,7 +114,7 @@ public abstract class ReactiveElasticsearchConfiguration extends ElasticsearchCo
 	}
 
 	/**
-	 * Provides the JsonpMapper that is used in the {@link #elasticsearchTransport(RestClient, JsonpMapper)} method and
+	 * Provides the JsonpMapper that is used in the {@link #elasticsearchTransport(Rest5Client, JsonpMapper)} method and
 	 * exposes it as a bean.
 	 *
 	 * @return the {@link JsonpMapper} to use
@@ -118,13 +122,20 @@ public abstract class ReactiveElasticsearchConfiguration extends ElasticsearchCo
 	 */
 	@Bean
 	public JsonpMapper jsonpMapper() {
-		return new JacksonJsonpMapper();
+		// we need to create our own objectMapper that keeps null values in order to provide the storeNullValue
+		// functionality. The one Elasticsearch would provide removes the nulls. We remove unwanted nulls before they get
+		// into this mapper, so we can safely keep them here.
+		JsonMapper jsonMapper = JsonMapper.builder()
+				.enable(JsonNodeFeature.WRITE_NULL_PROPERTIES)
+				.enable(JsonNodeFeature.READ_NULL_PROPERTIES)
+				.build();
+		return new Jackson3JsonpMapper(jsonMapper);
 	}
 
 	/**
 	 * @return the options that should be added to every request. Must not be {@literal null}
 	 */
 	public TransportOptions transportOptions() {
-		return new RestClientOptions(RequestOptions.DEFAULT, false).toBuilder().build();
+		return new Rest5ClientOptions(RequestOptions.DEFAULT, false);
 	}
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchIndicesClient.java

@@ -25,7 +25,7 @@ import reactor.core.publisher.Mono;
 
 import java.util.function.Function;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Reactive version of the {@link co.elastic.clients.elasticsearch.indices.ElasticsearchIndicesClient}
@@ -539,14 +539,6 @@ public class ReactiveElasticsearchIndicesClient
 		return stats(builder -> builder);
 	}
 
-	public Mono<UnfreezeResponse> unfreeze(UnfreezeRequest request) {
-		return Mono.fromFuture(transport.performRequestAsync(request, UnfreezeRequest._ENDPOINT, transportOptions));
-	}
-
-	public Mono<UnfreezeResponse> unfreeze(Function<UnfreezeRequest.Builder, ObjectBuilder<UnfreezeRequest>> fn) {
-		return unfreeze(fn.apply(new UnfreezeRequest.Builder()).build());
-	}
-
 	public Mono<UpdateAliasesResponse> updateAliases(UpdateAliasesRequest request) {
 		return Mono.fromFuture(transport.performRequestAsync(request, UpdateAliasesRequest._ENDPOINT, transportOptions));
 	}

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchLegacyRestClientConfiguration.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2021-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.elasticsearch.client.elc;
+
+import co.elastic.clients.json.JsonpMapper;
+import co.elastic.clients.json.jackson.JacksonJsonpMapper;
+import co.elastic.clients.transport.ElasticsearchTransport;
+import co.elastic.clients.transport.TransportOptions;
+import co.elastic.clients.transport.rest_client.RestClientOptions;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import org.elasticsearch.client.RequestOptions;
+import org.elasticsearch.client.RestClient;
+import org.springframework.context.annotation.Bean;
+import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.client.elc.rest_client.RestClients;
+import org.springframework.data.elasticsearch.config.ElasticsearchConfigurationSupport;
+import org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations;
+import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
+import org.springframework.util.Assert;
+
+/**
+ * Base class for a @{@link org.springframework.context.annotation.Configuration} class to set up the Elasticsearch
+ * connection using the {@link ReactiveElasticsearchClient}. This class exposes different parts of the setup as Spring
+ * beans. Deriving * classes must provide the {@link ClientConfiguration} to use. <br/>
+ * This class uses the Elasticsearch RestClient which was replaced b y the Rest5Client in Elasticsearch 9. It is still
+ * available here but deprecated. *
+ *
+ * @author Peter-Josef Meisch
+ * @since 4.4
+ * @deprecated since 6.0 use {@link ReactiveElasticsearchConfiguration}
+ */
+@Deprecated(since = "6.0", forRemoval=true)
+public abstract class ReactiveElasticsearchLegacyRestClientConfiguration extends ElasticsearchConfigurationSupport {
+
+	/**
+	 * Must be implemented by deriving classes to provide the {@link ClientConfiguration}.
+	 *
+	 * @return configuration, must not be {@literal null}
+	 */
+	@Bean(name = "elasticsearchClientConfiguration")
+	public abstract ClientConfiguration clientConfiguration();
+
+	/**
+	 * Provides the underlying low level RestClient.
+	 *
+	 * @param clientConfiguration configuration for the client, must not be {@literal null}
+	 * @return RestClient
+	 */
+	@Bean
+	public RestClient elasticsearchRestClient(ClientConfiguration clientConfiguration) {
+
+		Assert.notNull(clientConfiguration, "clientConfiguration must not be null");
+
+		return RestClients.getRestClient(clientConfiguration);
+	}
+
+	/**
+	 * Provides the Elasticsearch transport to be used. The default implementation uses the {@link RestClient} bean and
+	 * the {@link JsonpMapper} bean provided in this class.
+	 *
+	 * @return the {@link ElasticsearchTransport}
+	 * @since 5.2
+	 */
+	@Bean
+	public ElasticsearchTransport elasticsearchTransport(RestClient restClient, JsonpMapper jsonpMapper) {
+
+		Assert.notNull(restClient, "restClient must not be null");
+		Assert.notNull(jsonpMapper, "jsonpMapper must not be null");
+
+		return ElasticsearchClients.getElasticsearchTransport(restClient, ElasticsearchClients.REACTIVE_CLIENT,
+				transportOptions(), jsonpMapper);
+	}
+
+	/**
+	 * Provides the {@link ReactiveElasticsearchClient} instance used.
+	 *
+	 * @param transport the ElasticsearchTransport to use
+	 * @return ReactiveElasticsearchClient instance.
+	 */
+	@Bean
+	public ReactiveElasticsearchClient reactiveElasticsearchClient(ElasticsearchTransport transport) {
+
+		Assert.notNull(transport, "transport must not be null");
+
+		return ElasticsearchClients.createReactive(transport);
+	}
+
+	/**
+	 * Creates {@link ReactiveElasticsearchOperations}.
+	 *
+	 * @return never {@literal null}.
+	 */
+	@Bean(name = { "reactiveElasticsearchOperations", "reactiveElasticsearchTemplate" })
+	public ReactiveElasticsearchOperations reactiveElasticsearchOperations(ElasticsearchConverter elasticsearchConverter,
+			ReactiveElasticsearchClient reactiveElasticsearchClient) {
+
+		ReactiveElasticsearchTemplate template = new ReactiveElasticsearchTemplate(reactiveElasticsearchClient,
+				elasticsearchConverter);
+		template.setRefreshPolicy(refreshPolicy());
+
+		return template;
+	}
+
+	/**
+	 * Provides the JsonpMapper that is used in the {@link #elasticsearchTransport(RestClient, JsonpMapper)} method and
+	 * exposes it as a bean.
+	 *
+	 * @return the {@link JsonpMapper} to use
+	 * @since 5.2
+	 */
+	@Bean
+	public JsonpMapper jsonpMapper() {
+		// we need to create our own objectMapper that keeps null values in order to provide the storeNullValue
+		// functionality. The one Elasticsearch would provide removes the nulls. We remove unwanted nulls before they get
+		// into this mapper, so we can safely keep them here.
+		var objectMapper = (new ObjectMapper())
+				.configure(SerializationFeature.INDENT_OUTPUT, false)
+				.setSerializationInclusion(JsonInclude.Include.ALWAYS);
+		return new JacksonJsonpMapper(objectMapper);
+	}
+
+	/**
+	 * @return the options that should be added to every request. Must not be {@literal null}
+	 */
+	public TransportOptions transportOptions() {
+		return new RestClientOptions(RequestOptions.DEFAULT, false).toBuilder().build();
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchSqlClient.java

@@ -27,7 +27,8 @@ import reactor.core.publisher.Mono;
 import java.io.IOException;
 import java.util.function.Function;
 
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
+
 
 /**
  * Reactive version of {@link co.elastic.clients.elasticsearch.sql.ElasticsearchSqlClient}.

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveElasticsearchTemplate.java

@@ -18,29 +18,13 @@ package org.springframework.data.elasticsearch.client.elc;
 import static co.elastic.clients.util.ApiTypeHelper.*;
 import static org.springframework.data.elasticsearch.client.elc.TypeUtils.*;
 
-import co.elastic.clients.elasticsearch._types.Result;
-import co.elastic.clients.elasticsearch.core.*;
-import co.elastic.clients.elasticsearch.core.bulk.BulkResponseItem;
-import co.elastic.clients.elasticsearch.core.search.ResponseBody;
-import co.elastic.clients.json.JsonpMapper;
-import co.elastic.clients.transport.Version;
-import co.elastic.clients.transport.endpoints.BooleanResponse;
-import reactor.core.publisher.Flux;
-import reactor.core.publisher.Mono;
-import reactor.util.function.Tuple2;
-
-import java.time.Duration;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.function.BiFunction;
-import java.util.function.Function;
-import java.util.stream.Collectors;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Publisher;
+import org.springframework.beans.BeansException;
+import org.springframework.context.ApplicationContext;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.elasticsearch.BulkFailureException;
 import org.springframework.data.elasticsearch.NoSuchIndexException;
@@ -51,6 +35,7 @@ import org.springframework.data.elasticsearch.core.AggregationContainer;
 import org.springframework.data.elasticsearch.core.IndexedObjectInformation;
 import org.springframework.data.elasticsearch.core.MultiGetItem;
 import org.springframework.data.elasticsearch.core.ReactiveIndexOperations;
+import org.springframework.data.elasticsearch.core.SearchHit;
 import org.springframework.data.elasticsearch.core.cluster.ReactiveClusterOperations;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.data.elasticsearch.core.document.Document;
@@ -63,11 +48,32 @@ import org.springframework.data.elasticsearch.core.reindex.ReindexRequest;
 import org.springframework.data.elasticsearch.core.reindex.ReindexResponse;
 import org.springframework.data.elasticsearch.core.script.Script;
 import org.springframework.data.elasticsearch.core.sql.SqlResponse;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 
+import java.time.Duration;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import co.elastic.clients.elasticsearch._types.Result;
+import co.elastic.clients.elasticsearch.core.*;
+import co.elastic.clients.elasticsearch.core.bulk.BulkResponseItem;
+import co.elastic.clients.elasticsearch.core.search.ResponseBody;
+import co.elastic.clients.json.JsonpMapper;
+import co.elastic.clients.transport.Version;
+import co.elastic.clients.transport.endpoints.BooleanResponse;
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationRegistry;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.util.function.Tuple2;
+
 /**
  * Implementation of {@link org.springframework.data.elasticsearch.core.ReactiveElasticsearchOperations} using the new
  * Elasticsearch client.
@@ -75,12 +81,15 @@ import org.springframework.util.StringUtils;
  * @author Peter-Josef Meisch
  * @author Illia Ulianov
  * @author Junghoon Ban
+ * @author maryantocinn
  * @since 4.4
  */
 public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearchTemplate {
 
 	private static final Log LOGGER = LogFactory.getLog(ReactiveElasticsearchTemplate.class);
 
+	@Nullable private ElasticsearchObservationConvention observationConvention;
+
 	private final ReactiveElasticsearchClient client;
 	private final ReactiveElasticsearchSqlClient sqlClient;
 	private final RequestConverter requestConverter;
@@ -101,7 +110,105 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		exceptionTranslator = new ElasticsearchExceptionTranslator(jsonpMapper);
 	}
 
+	@Override
+	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
+
+		super.setApplicationContext(applicationContext);
+
+		if (observationRegistry == ObservationRegistry.NOOP) {
+			applicationContext.getBeanProvider(ObservationRegistry.class).ifAvailable(this::setObservationRegistry);
+		}
+
+		if (observationConvention == null) {
+			applicationContext.getBeanProvider(ElasticsearchObservationConvention.class)
+					.ifAvailable(this::setObservationConvention);
+		}
+	}
+
+	/**
+	 * Set a custom {@link ElasticsearchObservationConvention} to override the default convention.
+	 *
+	 * @param observationConvention can be {@literal null}.
+	 * @since 6.1
+	 */
+	public void setObservationConvention(@Nullable ElasticsearchObservationConvention observationConvention) {
+		this.observationConvention = observationConvention;
+	}
+
+	private <T> Mono<T> observeMono(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			Mono<T> mono) {
+		return Mono.defer(() -> {
+			Observation observation = createObservation(operationName, index, null);
+			return mono.doOnError(observation::error) //
+					.doFinally(signalType -> observation.stop())
+					.contextWrite(context -> context.put(Observation.class, observation))
+					.doOnSubscribe(subscription -> observation.start());
+		});
+	}
+
+	private <T> Flux<T> observeFlux(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			Flux<T> flux) {
+		return Flux.defer(() -> {
+			Observation observation = createObservation(operationName, index, null);
+			return flux.doOnError(observation::error) //
+					.doFinally(signalType -> observation.stop())
+					.contextWrite(context -> context.put(Observation.class, observation))
+					.doOnSubscribe(subscription -> observation.start());
+		});
+	}
+
+	private <T> Mono<T> observeMono(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			int batchSize, Mono<T> mono) {
+		return Mono.defer(() -> {
+			Observation observation = createObservation(operationName, index, batchSize);
+			return mono.doOnError(observation::error) //
+					.doFinally(signalType -> observation.stop())
+					.contextWrite(context -> context.put(Observation.class, observation))
+					.doOnSubscribe(subscription -> observation.start());
+		});
+	}
+
+	private Observation createObservation(ElasticsearchOperationName operationName, @Nullable IndexCoordinates index,
+			@Nullable Integer batchSize) {
+
+		ElasticsearchObservationContext context = new ElasticsearchObservationContext(operationName, index);
+		context.setBatchSize(batchSize);
+
+		return ElasticsearchObservation.ELASTICSEARCH_COMMAND_OBSERVATION.observation(observationConvention,
+				DefaultElasticsearchObservationConvention.INSTANCE, () -> context, observationRegistry);
+	}
+
 	// region Document operations
+	@Override
+	public <T> Mono<T> save(T entity, IndexCoordinates index) {
+		return observeMono(ElasticsearchOperationName.SAVE, index, super.save(entity, index));
+	}
+
+	@Override
+	public Mono<Boolean> exists(String id, IndexCoordinates index) {
+		return observeMono(ElasticsearchOperationName.EXISTS, index, super.exists(id, index));
+	}
+
+	@Override
+	public Mono<String> delete(Object entity, IndexCoordinates index) {
+		return observeMono(ElasticsearchOperationName.DELETE, index, super.delete(entity, index));
+	}
+
+	@Override
+	public Mono<String> delete(String id, IndexCoordinates index) {
+		return observeMono(ElasticsearchOperationName.DELETE, index, super.delete(id, index));
+	}
+
+	@Override
+	public <T> Flux<SearchHit<T>> search(Query query, Class<?> entityType, Class<T> resultType, IndexCoordinates index) {
+		return observeFlux(ElasticsearchOperationName.SEARCH, index, super.search(query, entityType, resultType, index));
+	}
+
+	@Override
+	public Mono<Long> count(Query query, Class<?> entityType, IndexCoordinates index) {
+		return observeMono(ElasticsearchOperationName.COUNT, index, super.count(query, entityType, index));
+	}
+
 	@Override
 	protected <T> Mono<Tuple2<T, IndexResponseMetaData>> doIndex(T entity, IndexCoordinates index) {
 
@@ -123,7 +230,7 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 
 		Assert.notNull(entitiesPublisher, "entitiesPublisher must not be null!");
 
-		return entitiesPublisher //
+		return observeFlux(ElasticsearchOperationName.BULK, index, entitiesPublisher //
 				.flatMapMany(entities -> Flux.fromIterable(entities) //
 						.concatMap(entity -> maybeCallbackBeforeConvert(entity, index)) //
 				).collectList() //
@@ -145,12 +252,12 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 												response.index(), //
 												response.seqNo(), //
 												response.primaryTerm(), //
-												response.version()),
-										converter,
+												response.version()), //
+										converter, //
 										routingResolver);
 								return maybeCallbackAfterSave(updatedEntity, index);
 							});
-				});
+				}));
 	}
 
 	@Override
@@ -162,7 +269,7 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		ExistsRequest existsRequest = requestConverter.documentExistsRequest(id, routingResolver.getRouting(), index);
 
 		return Mono.from(execute(
-				((ClientCallback<Publisher<BooleanResponse>>) client -> client.exists(existsRequest))))
+				((ClientCallback<@NonNull Publisher<BooleanResponse>>) client -> client.exists(existsRequest))))
 				.map(BooleanResponse::value) //
 				.onErrorReturn(NoSuchIndexException.class, false);
 	}
@@ -171,9 +278,11 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 	public Mono<ByQueryResponse> delete(DeleteQuery query, Class<?> entityType, IndexCoordinates index) {
 		Assert.notNull(query, "query must not be null");
 
-		DeleteByQueryRequest request = requestConverter.documentDeleteByQueryRequest(query, routingResolver.getRouting(),
-				entityType, index, getRefreshPolicy());
-		return Mono.from(execute(client -> client.deleteByQuery(request))).map(responseConverter::byQueryResponse);
+		return observeMono(ElasticsearchOperationName.DELETE_BY_QUERY, index, Mono.defer(() -> {
+			DeleteByQueryRequest request = requestConverter.documentDeleteByQueryRequest(query, routingResolver.getRouting(),
+					entityType, index, getRefreshPolicy());
+			return Mono.from(execute(client -> client.deleteByQuery(request))).map(responseConverter::byQueryResponse);
+		}));
 	}
 
 	@Override
@@ -183,13 +292,15 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		Assert.notNull(entityType, "entityType must not be null");
 		Assert.notNull(index, "index must not be null");
 
-		GetRequest getRequest = requestConverter.documentGetRequest(id, routingResolver.getRouting(), index);
+		return observeMono(ElasticsearchOperationName.GET, index, Mono.defer(() -> {
+			GetRequest getRequest = requestConverter.documentGetRequest(id, routingResolver.getRouting(), index);
 
-		Mono<GetResponse<EntityAsMap>> getResponse = Mono
-				.from(execute(client -> client.get(getRequest, EntityAsMap.class)));
+			Mono<GetResponse<EntityAsMap>> getResponse = Mono //
+					.from(execute(client -> client.get(getRequest, EntityAsMap.class)));
 
-		ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(converter, entityType, index);
-		return getResponse.flatMap(response -> callback.toEntity(DocumentAdapters.from(response)));
+			ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(converter, entityType, index);
+			return getResponse.flatMap(response -> callback.toEntity(DocumentAdapters.from(response)));
+		}));
 	}
 
 	@Override
@@ -226,13 +337,15 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		Assert.notNull(updateQuery, "UpdateQuery must not be null");
 		Assert.notNull(index, "Index must not be null");
 
-		UpdateRequest<Document, ?> request = requestConverter.documentUpdateRequest(updateQuery, index, getRefreshPolicy(),
-				routingResolver.getRouting());
+		return observeMono(ElasticsearchOperationName.UPDATE, index, Mono.defer(() -> {
+			UpdateRequest<Document, ?> request = requestConverter.documentUpdateRequest(updateQuery, index,
+					getRefreshPolicy(), routingResolver.getRouting());
 
-		return Mono.from(execute(client -> client.update(request, Document.class))).flatMap(response -> {
-			UpdateResponse.Result result = result(response.result());
-			return result == null ? Mono.empty() : Mono.just(UpdateResponse.of(result));
-		});
+			return Mono.from(execute(client -> client.update(request, Document.class))).flatMap(response -> {
+				UpdateResponse.Result result = result(response.result());
+				return result == null ? Mono.empty() : Mono.just(UpdateResponse.of(result));
+			});
+		}));
 	}
 
 	@Override
@@ -247,7 +360,8 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		Assert.notNull(bulkOptions, "BulkOptions must not be null");
 		Assert.notNull(index, "Index must not be null");
 
-		return doBulkOperation(queries, bulkOptions, index).then();
+		return observeMono(ElasticsearchOperationName.BULK, index, queries.size(),
+				doBulkOperation(queries, bulkOptions, index).then());
 	}
 
 	private Flux<BulkResponseItem> doBulkOperation(List<?> queries, BulkOptions bulkOptions, IndexCoordinates index) {
@@ -310,22 +424,24 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		Assert.notNull(query, "query must not be null");
 		Assert.notNull(clazz, "clazz must not be null");
 
-		MgetRequest request = requestConverter.documentMgetRequest(query, clazz, index);
+		return observeFlux(ElasticsearchOperationName.MULTI_GET, index, Flux.defer(() -> {
+			MgetRequest request = requestConverter.documentMgetRequest(query, clazz, index);
 
-		ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(converter, clazz, index);
+			ReadDocumentCallback<T> callback = new ReadDocumentCallback<>(converter, clazz, index);
 
-		Publisher<MgetResponse<EntityAsMap>> response = execute(client -> client.mget(request, EntityAsMap.class));
+			Publisher<MgetResponse<EntityAsMap>> response = execute(client -> client.mget(request, EntityAsMap.class));
 
-		return Mono.from(response)//
-				.flatMapMany(it -> Flux.fromIterable(DocumentAdapters.from(it))) //
-				.flatMap(multiGetItem -> {
-					if (multiGetItem.isFailed()) {
-						return Mono.just(MultiGetItem.of(null, multiGetItem.getFailure()));
-					} else {
-						return callback.toEntity(multiGetItem.getItem()) //
-								.map(t -> MultiGetItem.of(t, multiGetItem.getFailure()));
-					}
-				});
+			return Mono.from(response)//
+					.flatMapMany(it -> Flux.fromIterable(DocumentAdapters.from(it))) //
+					.flatMap(multiGetItem -> {
+						if (multiGetItem.isFailed()) {
+							return Mono.just(MultiGetItem.of(null, multiGetItem.getFailure()));
+						} else {
+							return callback.toEntity(multiGetItem.getItem()) //
+									.map(t -> MultiGetItem.of(t, multiGetItem.getFailure()));
+						}
+					});
+		}));
 	}
 
 	// endregion
@@ -335,6 +451,14 @@ public class ReactiveElasticsearchTemplate extends AbstractReactiveElasticsearch
 		return new ReactiveElasticsearchTemplate(client, converter);
 	}
 
+	@Override
+	protected void customizeCopy(AbstractReactiveElasticsearchTemplate copy) {
+
+		if (copy instanceof ReactiveElasticsearchTemplate reactiveTemplate) {
+			reactiveTemplate.observationConvention = this.observationConvention;
+		}
+	}
+
 	// region search operations
 
 	@Override

src/main/java/org/springframework/data/elasticsearch/client/elc/ReactiveIndicesTemplate.java

@@ -21,6 +21,7 @@ import co.elastic.clients.elasticsearch._types.AcknowledgedResponseBase;
 import co.elastic.clients.elasticsearch.indices.*;
 import co.elastic.clients.transport.ElasticsearchTransport;
 import co.elastic.clients.transport.endpoints.BooleanResponse;
+import org.springframework.data.elasticsearch.ResourceNotFoundException;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -29,6 +30,7 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.elasticsearch.NoSuchIndexException;
@@ -51,7 +53,6 @@ import org.springframework.data.elasticsearch.core.mapping.Alias;
 import org.springframework.data.elasticsearch.core.mapping.CreateIndexSettings;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -389,7 +390,8 @@ public class ReactiveIndicesTemplate
 		co.elastic.clients.elasticsearch.indices.GetTemplateRequest getTemplateRequestES = requestConverter
 				.indicesGetTemplateRequest(getTemplateRequest);
 		Mono<GetTemplateResponse> getTemplateResponse = Mono
-				.from(execute(client -> client.getTemplate(getTemplateRequestES)));
+				.from(execute(client -> client.getTemplate(getTemplateRequestES)))
+                .onErrorComplete(ResourceNotFoundException.class);
 
 		return getTemplateResponse.flatMap(response -> {
 			if (response != null) {

src/main/java/org/springframework/data/elasticsearch/client/elc/RequestConverter.java

@@ -42,10 +42,10 @@ import co.elastic.clients.elasticsearch.core.bulk.CreateOperation;
 import co.elastic.clients.elasticsearch.core.bulk.IndexOperation;
 import co.elastic.clients.elasticsearch.core.bulk.UpdateOperation;
 import co.elastic.clients.elasticsearch.core.mget.MultiGetOperation;
-import co.elastic.clients.elasticsearch.core.msearch.MultisearchBody;
 import co.elastic.clients.elasticsearch.core.msearch.MultisearchHeader;
 import co.elastic.clients.elasticsearch.core.search.Highlight;
 import co.elastic.clients.elasticsearch.core.search.Rescore;
+import co.elastic.clients.elasticsearch.core.search.SearchRequestBody;
 import co.elastic.clients.elasticsearch.core.search.SourceConfig;
 import co.elastic.clients.elasticsearch.indices.*;
 import co.elastic.clients.elasticsearch.indices.ExistsIndexTemplateRequest;
@@ -77,7 +77,7 @@ import java.util.stream.Stream;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.elasticsearch.core.RefreshPolicy;
@@ -101,7 +101,6 @@ import org.springframework.data.elasticsearch.core.reindex.ReindexRequest;
 import org.springframework.data.elasticsearch.core.reindex.Remote;
 import org.springframework.data.elasticsearch.core.script.Script;
 import org.springframework.data.elasticsearch.support.DefaultStringObjectMap;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
@@ -310,7 +309,6 @@ class RequestConverter extends AbstractQueryProcessor {
 		return updateAliasRequestBuilder.build();
 	}
 
-	@NotNull
 	private Action.Builder getBuilder(AliasAction aliasAction) {
 		Action.Builder actionBuilder = new Action.Builder();
 
@@ -723,20 +721,18 @@ class RequestConverter extends AbstractQueryProcessor {
 			return a;
 		});
 
-		uob //
-				.routing(query.getRouting()) //
-				.ifSeqNo(query.getIfSeqNo() != null ? Long.valueOf(query.getIfSeqNo()) : null) //
-				.ifPrimaryTerm(query.getIfPrimaryTerm() != null ? Long.valueOf(query.getIfPrimaryTerm()) : null) //
-				.retryOnConflict(query.getRetryOnConflict()) //
-		;
+		uob
+				.routing(query.getRouting())
+				.ifSeqNo(query.getIfSeqNo())
+				.ifPrimaryTerm(query.getIfPrimaryTerm())
+				.retryOnConflict(query.getRetryOnConflict());
 
 		// no refresh, timeout, waitForActiveShards on UpdateOperation or UpdateAction
 
 		return uob.build();
 	}
 
-	@Nullable
-	private co.elastic.clients.elasticsearch._types.Script getScript(@Nullable ScriptData scriptData) {
+	private co.elastic.clients.elasticsearch._types.@Nullable Script getScript(@Nullable ScriptData scriptData) {
 
 		if (scriptData == null) {
 			return null;
@@ -749,11 +745,10 @@ class RequestConverter extends AbstractQueryProcessor {
 		}
 		return co.elastic.clients.elasticsearch._types.Script.of(sb -> {
 			sb.lang(scriptData.language())
-					.params(params);
-			if (scriptData.type() == ScriptType.INLINE) {
-				sb.source(scriptData.script());
-			} else if (scriptData.type() == ScriptType.STORED) {
-				sb.id(scriptData.script());
+					.params(params)
+					.id(scriptData.scriptName());
+			if (scriptData.script() != null) {
+				sb.source(s -> s.scriptString(scriptData.script()));
 			}
 			return sb;
 		});
@@ -905,8 +900,17 @@ class RequestConverter extends AbstractQueryProcessor {
 					}
 
 					SourceFilter sourceFilter = source.getSourceFilter();
-					if (sourceFilter != null && sourceFilter.getIncludes() != null) {
-						s.sourceFields(Arrays.asList(sourceFilter.getIncludes()));
+					if (sourceFilter != null && (sourceFilter.getIncludes() != null || sourceFilter.getExcludes() != null)) {
+						s.sourceFields(cfg -> cfg
+								.filter(f -> {
+									if (sourceFilter.getIncludes() != null) {
+										f.includes(Arrays.asList(sourceFilter.getIncludes()));
+									}
+									if (sourceFilter.getExcludes() != null) {
+										f.excludes(Arrays.asList(sourceFilter.getExcludes()));
+									}
+									return f;
+								}));
 					}
 					return s;
 				}) //
@@ -925,9 +929,13 @@ class RequestConverter extends AbstractQueryProcessor {
 
 		ReindexRequest.Script script = reindexRequest.getScript();
 		if (script != null) {
-			builder.script(sb -> sb
-					.lang(script.getLang())
-					.source(script.getSource()));
+			builder.script(sb -> {
+				if (script.getSource() != null) {
+					sb.source(s -> s.scriptString(script.getSource()));
+				}
+				sb.lang(script.getLang());
+				return sb;
+			});
 		}
 
 		builder.timeout(time(reindexRequest.getTimeout())) //
@@ -1064,7 +1072,10 @@ class RequestConverter extends AbstractQueryProcessor {
 		return UpdateRequest.of(uqb -> {
 			uqb.index(indexName).id(query.getId());
 
-			if (query.getScript() != null) {
+			var scriptData = query.getScriptData();
+			var script = scriptData != null ? scriptData.script() : null;
+
+			if (script != null) {
 				Map<String, JsonData> params = new HashMap<>();
 
 				if (query.getParams() != null) {
@@ -1072,28 +1083,29 @@ class RequestConverter extends AbstractQueryProcessor {
 				}
 
 				uqb.script(sb -> {
-					sb.lang(query.getLang()).params(params);
+					sb
+							.lang(scriptData.language())
+							.params(params);
 
-					if (query.getScriptType() == ScriptType.INLINE) {
-						sb.source(query.getScript()); //
-					} else if (query.getScriptType() == ScriptType.STORED) {
-						sb.id(query.getScript());
+					if (script != null) {
+						sb.source(s -> s.scriptString(script));
 					}
+					sb.id(scriptData.scriptName());
+
 					return sb;
 				});
 			}
 
-			uqb //
-					.doc(query.getDocument()) //
-					.upsert(query.getUpsert()) //
-					.routing(query.getRouting() != null ? query.getRouting() : routing) //
-					.scriptedUpsert(query.getScriptedUpsert()) //
-					.docAsUpsert(query.getDocAsUpsert()) //
-					.ifSeqNo(query.getIfSeqNo() != null ? Long.valueOf(query.getIfSeqNo()) : null) //
-					.ifPrimaryTerm(query.getIfPrimaryTerm() != null ? Long.valueOf(query.getIfPrimaryTerm()) : null) //
-					.refresh(query.getRefreshPolicy() != null ? refresh(query.getRefreshPolicy()) : refresh(refreshPolicy)) //
-					.retryOnConflict(query.getRetryOnConflict()) //
-			;
+			uqb
+					.doc(query.getDocument())
+					.upsert(query.getUpsert())
+					.routing(query.getRouting() != null ? query.getRouting() : routing)
+					.scriptedUpsert(query.getScriptedUpsert())
+					.docAsUpsert(query.getDocAsUpsert())
+					.ifSeqNo(query.getIfSeqNo())
+					.ifPrimaryTerm(query.getIfPrimaryTerm())
+					.refresh(query.getRefreshPolicy() != null ? refresh(query.getRefreshPolicy()) : refresh(refreshPolicy))
+					.retryOnConflict(query.getRetryOnConflict());
 
 			if (query.getFetchSource() != null) {
 				uqb.source(sc -> sc.fetch(query.getFetchSource()));
@@ -1127,8 +1139,7 @@ class RequestConverter extends AbstractQueryProcessor {
 			}
 
 			return uqb;
-		} //
-		);
+		});
 	}
 
 	public UpdateByQueryRequest documentUpdateByQueryRequest(UpdateQuery updateQuery, IndexCoordinates index,
@@ -1241,11 +1252,11 @@ class RequestConverter extends AbstractQueryProcessor {
 				mtrb.searchTemplates(stb -> stb
 						.header(msearchHeaderBuilder(query, param.index(), routing))
 						.body(bb -> {
-							bb //
-									.explain(query.getExplain()) //
-									.id(query.getId()) //
-									.source(query.getSource()) //
-							;
+							bb.explain(query.getExplain()) //
+									.id(query.getId()); //
+							if (query.getSource() != null) {
+								bb.source(s -> s.scriptString(query.getSource()));
+							}
 
 							if (!CollectionUtils.isEmpty(query.getParams())) {
 								Map<String, JsonData> params = getTemplateParams(query.getParams().entrySet());
@@ -1329,7 +1340,9 @@ class RequestConverter extends AbstractQueryProcessor {
 
 										if (script != null) {
 											rfb.script(s -> {
-												s.source(script);
+												if (script != null) {
+													s.source(so -> so.scriptString(script));
+												}
 
 												if (runtimeField.getParams() != null) {
 													s.params(TypeUtils.paramsMap(runtimeField.getParams()));
@@ -1422,6 +1435,7 @@ class RequestConverter extends AbstractQueryProcessor {
 				.searchType(searchType) //
 				.timeout(timeStringMs(query.getTimeout())) //
 				.requestCache(query.getRequestCache()) //
+				.includeNamedQueriesScore(query.getIncludeNamedQueriesScore()) //
 		;
 
 		var pointInTime = query.getPointInTime();
@@ -1525,7 +1539,9 @@ class RequestConverter extends AbstractQueryProcessor {
 						String script = runtimeField.getScript();
 						if (script != null) {
 							rfb.script(s -> {
-								s.source(script);
+								if (script != null) {
+									s.source(so -> so.scriptString(script));
+								}
 
 								if (runtimeField.getParams() != null) {
 									s.params(TypeUtils.paramsMap(runtimeField.getParams()));
@@ -1622,7 +1638,7 @@ class RequestConverter extends AbstractQueryProcessor {
 		builder.highlight(highlight);
 	}
 
-	private void addHighlight(Query query, MultisearchBody.Builder builder) {
+	private void addHighlight(Query query, SearchRequestBody.Builder builder) {
 
 		Highlight highlight = query.getHighlightQuery()
 				.map(highlightQuery -> new HighlightQueryBuilder(elasticsearchConverter.getMappingContext(), this)
@@ -1702,7 +1718,7 @@ class RequestConverter extends AbstractQueryProcessor {
 	}
 
 	@Nullable
-	private NestedSortValue getNestedSort(@Nullable Order.Nested nested,
+	private NestedSortValue getNestedSort(Order.@Nullable Nested nested,
 			@Nullable ElasticsearchPersistentEntity<?> persistentEntity) {
 		return (nested == null || persistentEntity == null) ? null
 				: NestedSortValue.of(b -> b //
@@ -1746,7 +1762,7 @@ class RequestConverter extends AbstractQueryProcessor {
 	}
 
 	@SuppressWarnings("DuplicatedCode")
-	private void prepareNativeSearch(NativeQuery query, MultisearchBody.Builder builder) {
+	private void prepareNativeSearch(NativeQuery query, SearchRequestBody.Builder builder) {
 
 		builder //
 				.suggest(query.getSuggester()) //
@@ -1766,8 +1782,7 @@ class RequestConverter extends AbstractQueryProcessor {
 		}
 	}
 
-	@Nullable
-	co.elastic.clients.elasticsearch._types.query_dsl.Query getQuery(@Nullable Query query,
+	co.elastic.clients.elasticsearch._types.query_dsl.@Nullable Query getQuery(@Nullable Query query,
 			@Nullable Class<?> clazz) {
 		return getEsQuery(query, (q) -> elasticsearchConverter.updateQuery(q, clazz));
 	}
@@ -1866,10 +1881,11 @@ class RequestConverter extends AbstractQueryProcessor {
 					.id(query.getId()) //
 					.index(Arrays.asList(index.getIndexNames())) //
 					.preference(query.getPreference()) //
-					.searchType(searchType(query.getSearchType())) //
-					.source(query.getSource()) //
-			;
+					.searchType(searchType(query.getSearchType())); //
 
+			if (query.getSource() != null) {
+				builder.source(so -> so.scriptString(query.getSource()));
+			}
 			if (query.getRoute() != null) {
 				builder.routing(query.getRoute());
 			} else if (StringUtils.hasText(routing)) {
@@ -1894,7 +1910,6 @@ class RequestConverter extends AbstractQueryProcessor {
 		});
 	}
 
-	@NotNull
 	private Map<String, JsonData> getTemplateParams(Set<Map.Entry<String, Object>> query) {
 		Function<Map.Entry<String, Object>, String> keyMapper = Map.Entry::getKey;
 		Function<Map.Entry<String, Object>, JsonData> valueMapper = entry -> JsonData.of(entry.getValue(), jsonpMapper);
@@ -1912,7 +1927,7 @@ class RequestConverter extends AbstractQueryProcessor {
 				.id(script.id()) //
 				.script(sb -> sb //
 						.lang(script.language()) //
-						.source(script.source())));
+						.source(s -> s.scriptString(script.source()))));
 	}
 
 	public GetScriptRequest scriptGet(String name) {
@@ -1990,7 +2005,6 @@ class RequestConverter extends AbstractQueryProcessor {
 					case INTERNAL -> VersionType.Internal;
 					case EXTERNAL -> VersionType.External;
 					case EXTERNAL_GTE -> VersionType.ExternalGte;
-					case FORCE -> VersionType.Force;
 				};
 			}
 		}

src/main/java/org/springframework/data/elasticsearch/client/elc/ResponseConverter.java

@@ -48,6 +48,7 @@ import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.ElasticsearchErrorCause;
 import org.springframework.data.elasticsearch.core.IndexInformation;
 import org.springframework.data.elasticsearch.core.MultiGetItem;
@@ -65,7 +66,6 @@ import org.springframework.data.elasticsearch.core.reindex.ReindexResponse;
 import org.springframework.data.elasticsearch.core.script.Script;
 import org.springframework.data.elasticsearch.core.sql.SqlResponse;
 import org.springframework.data.elasticsearch.support.DefaultStringObjectMap;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -191,7 +191,7 @@ class ResponseConverter {
 		Assert.notNull(getMappingResponse, "getMappingResponse must not be null");
 		Assert.notNull(indexCoordinates, "indexCoordinates must not be null");
 
-		Map<String, IndexMappingRecord> mappings = getMappingResponse.result();
+		Map<String, IndexMappingRecord> mappings = getMappingResponse.mappings();
 
 		if (mappings == null || mappings.isEmpty()) {
 			return Document.create();
@@ -219,7 +219,7 @@ class ResponseConverter {
 
 		List<IndexInformation> indexInformationList = new ArrayList<>();
 
-		getIndexResponse.result().forEach((indexName, indexState) -> {
+		getIndexResponse.indices().forEach((indexName, indexState) -> {
 			Settings settings = indexState.settings() != null ? Settings.parse(toJson(indexState.settings(), jsonpMapper))
 					: new Settings();
 			Document mappings = indexState.mappings() != null ? Document.parse(toJson(indexState.mappings(), jsonpMapper))
@@ -239,7 +239,7 @@ class ResponseConverter {
 		Assert.notNull(getAliasResponse, "getAliasResponse must not be null");
 
 		Map<String, Set<AliasData>> aliasDataMap = new HashMap<>();
-		getAliasResponse.result().forEach((indexName, alias) -> {
+		getAliasResponse.aliases().forEach((indexName, alias) -> {
 			Set<AliasData> aliasDataSet = new HashSet<>();
 			alias.aliases()
 					.forEach((aliasName, aliasDefinition) -> aliasDataSet.add(indicesGetAliasData(aliasName, aliasDefinition)));
@@ -415,8 +415,7 @@ class ResponseConverter {
 				.withErrorCause(toErrorCause(failure.cause())).build();
 	}
 
-	@Nullable
-	public static MultiGetItem.Failure getFailure(MultiGetResponseItem<EntityAsMap> itemResponse) {
+	public static MultiGetItem.@Nullable Failure getFailure(MultiGetResponseItem<EntityAsMap> itemResponse) {
 
 		MultiGetError responseFailure = itemResponse.isFailure() ? itemResponse.failure() : null;
 
@@ -536,7 +535,7 @@ class ResponseConverter {
 				? Script.builder() //
 						.withId(response.id()) //
 						.withLanguage(response.script().lang()) //
-						.withSource(response.script().source()).build() //
+						.withSource(response.script().source().scriptString()).build() //
 				: null;
 	}
 	// endregion

src/main/java/org/springframework/data/elasticsearch/client/elc/SearchDocumentResponseBuilder.java

@@ -39,6 +39,7 @@ import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.SearchShardStatistics;
 import org.springframework.data.elasticsearch.core.TotalHitsRelation;
 import org.springframework.data.elasticsearch.core.document.SearchDocument;
@@ -48,7 +49,6 @@ import org.springframework.data.elasticsearch.core.suggest.response.PhraseSugges
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
 import org.springframework.data.elasticsearch.core.suggest.response.TermSuggestion;
 import org.springframework.data.elasticsearch.support.ScoreDoc;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 
@@ -133,7 +133,8 @@ class SearchDocumentResponseBuilder {
 	 * @return the {@link SearchDocumentResponse}
 	 */
 	public static <T> SearchDocumentResponse from(HitsMetadata<?> hitsMetadata, @Nullable ShardStatistics shards,
-			@Nullable String scrollId, @Nullable String pointInTimeId, long executionDurationInMillis, @Nullable Map<String, Aggregate> aggregations,
+			@Nullable String scrollId, @Nullable String pointInTimeId, long executionDurationInMillis,
+			@Nullable Map<String, Aggregate> aggregations,
 			Map<String, List<Suggestion<EntityAsMap>>> suggestES, SearchDocumentResponse.EntityCreator<T> entityCreator,
 			JsonpMapper jsonpMapper) {
 
@@ -171,7 +172,8 @@ class SearchDocumentResponseBuilder {
 
 		SearchShardStatistics shardStatistics = shards != null ? shardsFrom(shards) : null;
 
-		return new SearchDocumentResponse(totalHits, totalHitsRelation, maxScore, executionDuration, scrollId, pointInTimeId, searchDocuments,
+		return new SearchDocumentResponse(totalHits, totalHitsRelation, maxScore, executionDuration, scrollId,
+				pointInTimeId, searchDocuments,
 				aggregationsContainer, suggest, shardStatistics);
 	}
 

src/main/java/org/springframework/data/elasticsearch/client/elc/TypeUtils.java

@@ -38,6 +38,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.elasticsearch.core.RefreshPolicy;
 import org.springframework.data.elasticsearch.core.document.Document;
@@ -52,7 +53,6 @@ import org.springframework.data.elasticsearch.core.query.UpdateResponse;
 import org.springframework.data.elasticsearch.core.query.types.ConflictsType;
 import org.springframework.data.elasticsearch.core.query.types.OperatorType;
 import org.springframework.data.elasticsearch.core.reindex.ReindexRequest;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -220,7 +220,7 @@ final class TypeUtils {
 	}
 
 	@Nullable
-	static SortOrder sortOrder(@Nullable Sort.Direction direction) {
+	static SortOrder sortOrder(Sort.@Nullable Direction direction) {
 
 		if (direction == null) {
 			return null;
@@ -301,7 +301,7 @@ final class TypeUtils {
 	}
 
 	@Nullable
-	static OpType opType(@Nullable IndexQuery.OpType opType) {
+	static OpType opType(IndexQuery.@Nullable OpType opType) {
 
 		if (opType != null) {
 			return switch (opType) {
@@ -325,8 +325,7 @@ final class TypeUtils {
 		};
 	}
 
-	@Nullable
-	static UpdateResponse.Result result(@Nullable Result result) {
+	static UpdateResponse.@Nullable Result result(@Nullable Result result) {
 
 		if (result == null) {
 			return null;
@@ -343,7 +342,7 @@ final class TypeUtils {
 	}
 
 	@Nullable
-	static ScoreMode scoreMode(@Nullable RescorerQuery.ScoreMode scoreMode) {
+	static ScoreMode scoreMode(RescorerQuery.@Nullable ScoreMode scoreMode) {
 
 		if (scoreMode == null) {
 			return null;
@@ -361,7 +360,7 @@ final class TypeUtils {
 	}
 
 	@Nullable
-	static SearchType searchType(@Nullable Query.SearchType searchType) {
+	static SearchType searchType(Query.@Nullable SearchType searchType) {
 
 		if (searchType == null) {
 			return null;
@@ -418,14 +417,13 @@ final class TypeUtils {
 
 	@Nullable
 	static VersionType versionType(
-			@Nullable org.springframework.data.elasticsearch.annotations.Document.VersionType versionType) {
+			org.springframework.data.elasticsearch.annotations.Document.@Nullable VersionType versionType) {
 
 		if (versionType != null) {
 			return switch (versionType) {
 				case INTERNAL -> VersionType.Internal;
 				case EXTERNAL -> VersionType.External;
 				case EXTERNAL_GTE -> VersionType.ExternalGte;
-				case FORCE -> VersionType.Force;
 			};
 		}
 
@@ -536,7 +534,7 @@ final class TypeUtils {
 	 * @param scoreMode spring-data-elasticsearch {@literal scoreMode}.
 	 * @return an Elasticsearch {@literal scoreMode}.
 	 */
-	static ChildScoreMode scoreMode(@Nullable HasChildQuery.ScoreMode scoreMode) {
+	static ChildScoreMode scoreMode(HasChildQuery.@Nullable ScoreMode scoreMode) {
 		if (scoreMode == null) {
 			return ChildScoreMode.None;
 		}

src/main/java/org/springframework/data/elasticsearch/client/elc/aot/ElasticsearchClientRuntimeHints.java

@@ -15,15 +15,10 @@
  */
 package org.springframework.data.elasticsearch.client.elc.aot;
 
-import co.elastic.clients.elasticsearch._types.mapping.RuntimeFieldType;
-import co.elastic.clients.elasticsearch._types.mapping.TypeMapping;
-import co.elastic.clients.elasticsearch.indices.IndexSettings;
-import co.elastic.clients.elasticsearch.indices.PutMappingRequest;
-import org.springframework.aot.hint.MemberCategory;
+import org.jspecify.annotations.Nullable;
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
-import org.springframework.aot.hint.TypeReference;
-import org.springframework.lang.Nullable;
+import org.springframework.util.ClassUtils;
 
 /**
  * runtime hints for the Elasticsearch client libraries, as these do not provide any of their own.
@@ -37,20 +32,24 @@ public class ElasticsearchClientRuntimeHints implements RuntimeHintsRegistrar {
 	public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 
 		hints.reflection()
-				.registerType(TypeReference.of(IndexSettings.class), builder -> builder.withField("_DESERIALIZER")) //
-				.registerType(TypeReference.of(PutMappingRequest.class), builder -> builder.withField("_DESERIALIZER")) //
-				.registerType(TypeReference.of(RuntimeFieldType.class), builder -> builder.withField("_DESERIALIZER"))//
-				.registerType(TypeReference.of(TypeMapping.class), builder -> builder.withField("_DESERIALIZER")) //
-		;
+				.registerTypeIfPresent(classLoader, "co.elastic.clients.elasticsearch.indices.IndexSettings",
+						builder -> builder.withField("_DESERIALIZER"))
+				.registerTypeIfPresent(classLoader, "co.elastic.clients.elasticsearch.indices.PutMappingRequest",
+						builder -> builder.withField("_DESERIALIZER"))
+				.registerTypeIfPresent(classLoader, "co.elastic.clients.elasticsearch._types.mapping.RuntimeFieldType",
+						builder -> builder.withField("_DESERIALIZER"))
+				.registerTypeIfPresent(classLoader, "co.elastic.clients.elasticsearch._types.mapping.TypeMapping",
+						builder -> builder.withField("_DESERIALIZER"));
 
-		hints.serialization() //
-				.registerType(org.apache.http.impl.auth.BasicScheme.class) //
-				.registerType(org.apache.http.impl.auth.RFC2617Scheme.class) //
-				.registerType(java.util.HashMap.class) //
-		;
+		if (ClassUtils.isPresent("org.apache.http.impl.auth.BasicScheme",
+				ElasticsearchClientRuntimeHints.class.getClassLoader())) {
+			hints.serialization()
+					.registerType(org.apache.http.impl.auth.BasicScheme.class)
+					.registerType(org.apache.http.impl.auth.RFC2617Scheme.class)
+					.registerType(java.util.HashMap.class);
+		}
 
 		hints.resources() //
-				.registerPattern("co/elastic/clients/version.properties") //
-		;
+				.registerPattern("co/elastic/clients/version.properties");
 	}
 }

src/main/java/org/springframework/data/elasticsearch/client/elc/aot/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.client.elc.aot;

src/main/java/org/springframework/data/elasticsearch/client/elc/package-info.java

@@ -18,6 +18,5 @@
  * This package contains classes that use the new Elasticsearch client library (co.elastic.clients:elasticsearch-java)
  * to access Elasticsearch.
  */
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.client.elc;

src/main/java/org/springframework/data/elasticsearch/client/elc/rest5_client/Rest5Clients.java

@@ -0,0 +1,308 @@
+package org.springframework.data.elasticsearch.client.elc.rest5_client;
+
+import co.elastic.clients.transport.TransportOptions;
+import co.elastic.clients.transport.TransportUtils;
+import co.elastic.clients.transport.rest5_client.Rest5ClientOptions;
+import co.elastic.clients.transport.rest5_client.low_level.RequestOptions;
+import co.elastic.clients.transport.rest5_client.low_level.Rest5Client;
+import co.elastic.clients.transport.rest5_client.low_level.Rest5ClientBuilder;
+
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.security.NoSuchAlgorithmException;
+import java.time.Duration;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+import javax.net.ssl.SSLContext;
+
+import org.apache.hc.client5.http.config.ConnectionConfig;
+import org.apache.hc.client5.http.config.RequestConfig;
+import org.apache.hc.client5.http.impl.async.HttpAsyncClientBuilder;
+import org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder;
+import org.apache.hc.client5.http.impl.routing.DefaultProxyRoutePlanner;
+import org.apache.hc.core5.http.Header;
+import org.apache.hc.core5.http.HttpHost;
+import org.apache.hc.core5.http.message.BasicHeader;
+import org.apache.hc.core5.http.nio.ssl.BasicClientTlsStrategy;
+import org.apache.hc.core5.util.Timeout;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
+import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.support.HttpHeaders;
+import org.springframework.util.Assert;
+
+/**
+ * Utility class containing the functions to create the Elasticsearch Rest5Client used from Elasticsearch 9 on.
+ *
+ * @since 6.0
+ */
+public final class Rest5Clients {
+
+	// values copied from Rest5ClientBuilder
+	public static final int DEFAULT_SOCKET_TIMEOUT_MILLIS = 30000;
+	public static final int DEFAULT_RESPONSE_TIMEOUT_MILLIS = 0; // meaning infinite
+
+	private Rest5Clients() {}
+
+	/**
+	 * Creates a low level {@link Rest5Client} for the given configuration.
+	 *
+	 * @param clientConfiguration must not be {@literal null}
+	 * @return the {@link Rest5Client}
+	 */
+	public static Rest5Client getRest5Client(ClientConfiguration clientConfiguration) {
+		return getRest5ClientBuilder(clientConfiguration).build();
+	}
+
+	private static Rest5ClientBuilder getRest5ClientBuilder(ClientConfiguration clientConfiguration) {
+
+		HttpHost[] httpHosts = getHttpHosts(clientConfiguration);
+		Rest5ClientBuilder builder = Rest5Client.builder(httpHosts);
+
+		if (clientConfiguration.getPathPrefix() != null) {
+			builder.setPathPrefix(clientConfiguration.getPathPrefix());
+		}
+
+		HttpHeaders headers = clientConfiguration.getDefaultHeaders();
+
+		if (!headers.isEmpty()) {
+			builder.setDefaultHeaders(toHeaderArray(headers));
+		}
+
+		// RestClientBuilder configuration callbacks from the consumer
+		for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurationCallback : clientConfiguration
+				.getClientConfigurers()) {
+			if (clientConfigurationCallback instanceof ElasticsearchRest5ClientConfigurationCallback configurationCallback) {
+				builder = configurationCallback.configure(builder);
+			}
+		}
+
+		Duration connectTimeout = clientConfiguration.getConnectTimeout();
+		Duration socketTimeout = clientConfiguration.getSocketTimeout();
+
+		builder.setHttpClientConfigCallback(httpAsyncClientBuilder -> {
+
+			if (clientConfiguration.getProxy().isPresent()) {
+				var proxy = clientConfiguration.getProxy().get();
+				try {
+					var proxyRoutePlanner = new DefaultProxyRoutePlanner(HttpHost.create(proxy));
+					httpAsyncClientBuilder.setRoutePlanner(proxyRoutePlanner);
+				} catch (URISyntaxException e) {
+					throw new RuntimeException(e);
+				}
+			}
+			httpAsyncClientBuilder.addRequestInterceptorFirst((request, entity, context) -> {
+				clientConfiguration.getHeadersSupplier().get().forEach((header, values) -> {
+					// The accept and content-type headers are already put on the request, despite this being the first
+					// interceptor.
+					if ("Accept".equalsIgnoreCase(header) || " Content-Type".equalsIgnoreCase(header)) {
+						request.removeHeaders(header);
+					}
+					values.forEach(value -> request.addHeader(header, value));
+				});
+			});
+
+			// add httpclient configurator callbacks provided by the configuration
+			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
+					.getClientConfigurers()) {
+				if (clientConfigurer instanceof ElasticsearchHttpClientConfigurationCallback httpClientConfigurer) {
+					httpAsyncClientBuilder = httpClientConfigurer.configure(httpAsyncClientBuilder);
+				}
+			}
+		});
+
+		builder.setConnectionConfigCallback(connectionConfigBuilder -> {
+
+			if (!connectTimeout.isNegative()) {
+				connectionConfigBuilder.setConnectTimeout(
+						Timeout.of(Math.toIntExact(connectTimeout.toMillis()), TimeUnit.MILLISECONDS));
+			}
+			if (!socketTimeout.isNegative()) {
+				var soTimeout = Timeout.of(Math.toIntExact(socketTimeout.toMillis()), TimeUnit.MILLISECONDS);
+				connectionConfigBuilder.setSocketTimeout(soTimeout);
+			} else {
+				connectionConfigBuilder.setSocketTimeout(Timeout.of(DEFAULT_SOCKET_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS));
+			}
+
+			// add connectionConfig configurator callbacks provided by the configuration
+			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
+					.getClientConfigurers()) {
+				if (clientConfigurer instanceof ElasticsearchConnectionConfigurationCallback connectionConfigurationCallback) {
+					connectionConfigBuilder = connectionConfigurationCallback.configure(connectionConfigBuilder);
+				}
+			}
+		});
+
+		builder.setConnectionManagerCallback(poolingAsyncClientConnectionManagerBuilder -> {
+
+			SSLContext sslContext = null;
+			try {
+				sslContext = clientConfiguration.getCaFingerprint().isPresent()
+						? TransportUtils.sslContextFromCaFingerprint(clientConfiguration.getCaFingerprint().get())
+						: (clientConfiguration.getSslContext().isPresent()
+								? clientConfiguration.getSslContext().get()
+								: SSLContext.getDefault());
+			} catch (NoSuchAlgorithmException e) {
+				throw new IllegalStateException("could not create the default ssl context", e);
+			}
+			poolingAsyncClientConnectionManagerBuilder.setTlsStrategy(new BasicClientTlsStrategy(sslContext));
+
+			// add connectionManager configurator callbacks provided by the configuration
+			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
+					.getClientConfigurers()) {
+				if (clientConfigurer instanceof ElasticsearchConnectionManagerCallback connectionManagerCallback) {
+					poolingAsyncClientConnectionManagerBuilder = connectionManagerCallback
+							.configure(poolingAsyncClientConnectionManagerBuilder);
+				}
+			}
+		});
+
+		builder.setRequestConfigCallback(requestConfigBuilder -> {
+
+			if (!socketTimeout.isNegative()) {
+				var soTimeout = Timeout.of(Math.toIntExact(socketTimeout.toMillis()), TimeUnit.MILLISECONDS);
+				requestConfigBuilder.setConnectionRequestTimeout(soTimeout);
+			} else {
+				requestConfigBuilder
+						.setConnectionRequestTimeout(Timeout.of(DEFAULT_RESPONSE_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS));
+			}
+			// add connectionConfig configurator callbacks provided by the configuration
+			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
+					.getClientConfigurers()) {
+				if (clientConfigurer instanceof ElasticsearchRequestConfigCallback requestConfigCallback) {
+					requestConfigBuilder = requestConfigCallback.configure(requestConfigBuilder);
+				}
+			}
+		});
+
+		return builder;
+	}
+
+	private static HttpHost @NonNull [] getHttpHosts(ClientConfiguration clientConfiguration) {
+		List<InetSocketAddress> hosts = clientConfiguration.getEndpoints();
+		boolean useSsl = clientConfiguration.useSsl();
+		return hosts.stream()
+				.map(it -> (useSsl ? "https" : "http") + "://" + it.getHostString() + ':' + it.getPort())
+				.map(URI::create)
+				.map(HttpHost::create)
+				.toArray(HttpHost[]::new);
+	}
+
+	private static Header[] toHeaderArray(HttpHeaders headers) {
+		return headers.entrySet().stream() //
+				.flatMap(entry -> entry.getValue().stream() //
+						.map(value -> new BasicHeader(entry.getKey(), value))) //
+				.toList().toArray(new Header[0]);
+	}
+
+	/**
+	 * {@link ClientConfiguration.ClientConfigurationCallback} to configure the Rest5Client client with a
+	 * {@link Rest5ClientBuilder}
+	 *
+	 * @since 6.0
+	 */
+	public interface ElasticsearchRest5ClientConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<Rest5ClientBuilder> {
+
+		static ElasticsearchRest5ClientConfigurationCallback from(
+				Function<Rest5ClientBuilder, Rest5ClientBuilder> rest5ClientBuilderCallback) {
+
+			Assert.notNull(rest5ClientBuilderCallback, "rest5ClientBuilderCallback must not be null");
+
+			return rest5ClientBuilderCallback::apply;
+		}
+
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the Elasticsearch Rest5Client's Http client with a {@link HttpAsyncClientBuilder}
+	 *
+	 * @since 6.0
+	 */
+	public interface ElasticsearchHttpClientConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<HttpAsyncClientBuilder> {
+
+		static Rest5Clients.ElasticsearchHttpClientConfigurationCallback from(
+				Function<HttpAsyncClientBuilder, HttpAsyncClientBuilder> httpClientBuilderCallback) {
+
+			Assert.notNull(httpClientBuilderCallback, "httpClientBuilderCallback must not be null");
+
+			return httpClientBuilderCallback::apply;
+		}
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the Elasticsearch Rest5Client's connection with a {@link ConnectionConfig.Builder}
+	 *
+	 * @since 6.0
+	 */
+	public interface ElasticsearchConnectionConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<ConnectionConfig.Builder> {
+
+		static ElasticsearchConnectionConfigurationCallback from(
+				Function<ConnectionConfig.Builder, ConnectionConfig.Builder> connectionConfigBuilderCallback) {
+
+			Assert.notNull(connectionConfigBuilderCallback, "connectionConfigBuilderCallback must not be null");
+
+			return connectionConfigBuilderCallback::apply;
+		}
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the Elasticsearch Rest5Client's connection manager with a {@link PoolingAsyncClientConnectionManagerBuilder}
+	 *
+	 * @since 6.0
+	 */
+	public interface ElasticsearchConnectionManagerCallback
+			extends ClientConfiguration.ClientConfigurationCallback<PoolingAsyncClientConnectionManagerBuilder> {
+
+		static ElasticsearchConnectionManagerCallback from(
+				Function<PoolingAsyncClientConnectionManagerBuilder, PoolingAsyncClientConnectionManagerBuilder> connectionManagerBuilderCallback) {
+
+			Assert.notNull(connectionManagerBuilderCallback, "connectionManagerBuilderCallback must not be null");
+
+			return connectionManagerBuilderCallback::apply;
+		}
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the Elasticsearch Rest5Client's connection manager with a {@link RequestConfig.Builder}
+	 *
+	 * @since 6.0
+	 */
+	public interface ElasticsearchRequestConfigCallback
+			extends ClientConfiguration.ClientConfigurationCallback<RequestConfig.Builder> {
+
+		static ElasticsearchRequestConfigCallback from(
+				Function<RequestConfig.Builder, RequestConfig.Builder> requestConfigBuilderCallback) {
+
+			Assert.notNull(requestConfigBuilderCallback, "requestConfigBuilderCallback must not be null");
+
+			return requestConfigBuilderCallback::apply;
+		}
+	}
+
+	public static Rest5ClientOptions.Builder getRest5ClientOptionsBuilder(@Nullable TransportOptions transportOptions) {
+
+		if (transportOptions instanceof Rest5ClientOptions rest5ClientOptions) {
+			return rest5ClientOptions.toBuilder();
+		}
+
+		var builder = new Rest5ClientOptions.Builder(RequestOptions.DEFAULT.toBuilder());
+
+		if (transportOptions != null) {
+			transportOptions.headers().forEach(header -> builder.addHeader(header.getKey(), header.getValue()));
+			transportOptions.queryParameters().forEach(builder::setParameter);
+			builder.onWarnings(transportOptions.onWarnings());
+		}
+
+		return builder;
+	}
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/rest5_client/package-info.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2025-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * This package contains related to the new (from Elasticsearch 9 on) Rest5Client. There are also classes copied over from Elasticsearch in order to have a Rest5ClientBuilder that allows to configure the http client.
+ */
+@org.jspecify.annotations.NullMarked
+package org.springframework.data.elasticsearch.client.elc.rest5_client;

src/main/java/org/springframework/data/elasticsearch/client/elc/rest_client/RestClients.java

@@ -0,0 +1,195 @@
+package org.springframework.data.elasticsearch.client.elc.rest_client;
+
+import co.elastic.clients.transport.TransportOptions;
+import co.elastic.clients.transport.TransportUtils;
+import co.elastic.clients.transport.rest_client.RestClientOptions;
+
+import java.net.InetSocketAddress;
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import org.apache.http.HttpHost;
+import org.apache.http.HttpRequest;
+import org.apache.http.HttpRequestInterceptor;
+import org.apache.http.client.config.RequestConfig;
+import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
+import org.apache.http.message.BasicHeader;
+import org.apache.http.protocol.HttpContext;
+import org.elasticsearch.client.RequestOptions;
+import org.elasticsearch.client.RestClient;
+import org.elasticsearch.client.RestClientBuilder;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
+import org.springframework.data.elasticsearch.client.ClientConfiguration;
+import org.springframework.data.elasticsearch.client.elc.ElasticsearchClients;
+import org.springframework.data.elasticsearch.support.HttpHeaders;
+import org.springframework.util.Assert;
+
+/**
+ * Utility class containing the functions to create the Elasticsearch RestClient used up to Elasticsearch 9.
+ *
+ * @since 6.0
+ * @deprecated since 6.0, use the new Rest5Client the code for that is in the package ../rest_client.
+ */
+@Deprecated(since = "6.0", forRemoval = true)
+public final class RestClients {
+
+	/**
+	 * Creates a low level {@link RestClient} for the given configuration.
+	 *
+	 * @param clientConfiguration must not be {@literal null}
+	 * @return the {@link RestClient}
+	 */
+	public static RestClient getRestClient(ClientConfiguration clientConfiguration) {
+		return getRestClientBuilder(clientConfiguration).build();
+	}
+
+	private static RestClientBuilder getRestClientBuilder(ClientConfiguration clientConfiguration) {
+		HttpHost[] httpHosts = getHttpHosts(clientConfiguration);
+		RestClientBuilder builder = RestClient.builder(httpHosts);
+
+		if (clientConfiguration.getPathPrefix() != null) {
+			builder.setPathPrefix(clientConfiguration.getPathPrefix());
+		}
+
+		HttpHeaders headers = clientConfiguration.getDefaultHeaders();
+
+		if (!headers.isEmpty()) {
+			builder.setDefaultHeaders(toHeaderArray(headers));
+		}
+
+		builder.setHttpClientConfigCallback(clientBuilder -> {
+			if (clientConfiguration.getCaFingerprint().isPresent()) {
+				clientBuilder
+						.setSSLContext(TransportUtils.sslContextFromCaFingerprint(clientConfiguration.getCaFingerprint().get()));
+			}
+			clientConfiguration.getSslContext().ifPresent(clientBuilder::setSSLContext);
+			clientConfiguration.getHostNameVerifier().ifPresent(clientBuilder::setSSLHostnameVerifier);
+			clientBuilder.addInterceptorLast(new CustomHeaderInjector(clientConfiguration.getHeadersSupplier()));
+
+			RequestConfig.Builder requestConfigBuilder = RequestConfig.custom();
+			Duration connectTimeout = clientConfiguration.getConnectTimeout();
+
+			if (!connectTimeout.isNegative()) {
+				requestConfigBuilder.setConnectTimeout(Math.toIntExact(connectTimeout.toMillis()));
+			}
+
+			Duration socketTimeout = clientConfiguration.getSocketTimeout();
+
+			if (!socketTimeout.isNegative()) {
+				requestConfigBuilder.setSocketTimeout(Math.toIntExact(socketTimeout.toMillis()));
+				requestConfigBuilder.setConnectionRequestTimeout(Math.toIntExact(socketTimeout.toMillis()));
+			}
+
+			clientBuilder.setDefaultRequestConfig(requestConfigBuilder.build());
+
+			clientConfiguration.getProxy().map(HttpHost::create).ifPresent(clientBuilder::setProxy);
+
+			for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurer : clientConfiguration
+					.getClientConfigurers()) {
+				if (clientConfigurer instanceof RestClients.ElasticsearchHttpClientConfigurationCallback restClientConfigurationCallback) {
+					clientBuilder = restClientConfigurationCallback.configure(clientBuilder);
+				}
+			}
+
+			return clientBuilder;
+		});
+
+		for (ClientConfiguration.ClientConfigurationCallback<?> clientConfigurationCallback : clientConfiguration
+				.getClientConfigurers()) {
+			if (clientConfigurationCallback instanceof ElasticsearchRestClientConfigurationCallback configurationCallback) {
+				builder = configurationCallback.configure(builder);
+			}
+		}
+		return builder;
+	}
+
+	private static HttpHost @NonNull [] getHttpHosts(ClientConfiguration clientConfiguration) {
+		List<InetSocketAddress> hosts = clientConfiguration.getEndpoints();
+		boolean useSsl = clientConfiguration.useSsl();
+		return hosts.stream()
+				.map(it -> (useSsl ? "https" : "http") + "://" + it.getHostString() + ':' + it.getPort())
+				.map(HttpHost::create).toArray(HttpHost[]::new);
+	}
+
+	private static org.apache.http.Header[] toHeaderArray(HttpHeaders headers) {
+		return headers.entrySet().stream() //
+				.flatMap(entry -> entry.getValue().stream() //
+						.map(value -> new BasicHeader(entry.getKey(), value))) //
+				.toArray(org.apache.http.Header[]::new);
+	}
+
+	/**
+	 * Interceptor to inject custom supplied headers.
+	 *
+	 * @since 4.4
+	 */
+	record CustomHeaderInjector(Supplier<HttpHeaders> headersSupplier) implements HttpRequestInterceptor {
+
+		@Override
+		public void process(HttpRequest request, HttpContext context) {
+			HttpHeaders httpHeaders = headersSupplier.get();
+
+			if (httpHeaders != null && !httpHeaders.isEmpty()) {
+				Arrays.stream(toHeaderArray(httpHeaders)).forEach(request::addHeader);
+			}
+		}
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the Elasticsearch RestClient's Http client with a {@link HttpAsyncClientBuilder}
+	 *
+	 * @since 4.4
+	 */
+	public interface ElasticsearchHttpClientConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<HttpAsyncClientBuilder> {
+
+		static RestClients.ElasticsearchHttpClientConfigurationCallback from(
+				Function<HttpAsyncClientBuilder, HttpAsyncClientBuilder> httpClientBuilderCallback) {
+
+			Assert.notNull(httpClientBuilderCallback, "httpClientBuilderCallback must not be null");
+
+			return httpClientBuilderCallback::apply;
+		}
+	}
+
+	/**
+	 * {@link org.springframework.data.elasticsearch.client.ClientConfiguration.ClientConfigurationCallback} to configure
+	 * the RestClient client with a {@link RestClientBuilder}
+	 *
+	 * @since 5.0
+	 */
+	public interface ElasticsearchRestClientConfigurationCallback
+			extends ClientConfiguration.ClientConfigurationCallback<RestClientBuilder> {
+
+		static ElasticsearchRestClientConfigurationCallback from(
+				Function<RestClientBuilder, RestClientBuilder> restClientBuilderCallback) {
+
+			Assert.notNull(restClientBuilderCallback, "restClientBuilderCallback must not be null");
+
+			return restClientBuilderCallback::apply;
+		}
+	}
+
+	public static RestClientOptions.Builder getRestClientOptionsBuilder(@Nullable TransportOptions transportOptions) {
+
+		if (transportOptions instanceof RestClientOptions restClientOptions) {
+			return restClientOptions.toBuilder();
+		}
+
+		var builder = new RestClientOptions.Builder(RequestOptions.DEFAULT.toBuilder());
+
+		if (transportOptions != null) {
+			transportOptions.headers().forEach(header -> builder.addHeader(header.getKey(), header.getValue()));
+			transportOptions.queryParameters().forEach(builder::setParameter);
+			builder.onWarnings(transportOptions.onWarnings());
+		}
+
+		return builder;
+	}
+
+}

src/main/java/org/springframework/data/elasticsearch/client/elc/rest_client/package-info.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-present the original author or authors.
+ * Copyright 2022-present the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,15 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.springframework.data.elasticsearch.core.query;
 
 /**
- * Define script types for update queries.
- *
- * @author Farid Faoudi
- * @since 4.2
+ * This package contains related to the old (up to Elasticsearch 9) RestClient.
  */
-
-public enum ScriptType {
-	INLINE, STORED
-}
+@Deprecated(since = "6.0", forRemoval=true)
+@org.jspecify.annotations.NullMarked
+package org.springframework.data.elasticsearch.client.elc.rest_client;

src/main/java/org/springframework/data/elasticsearch/client/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.client;

src/main/java/org/springframework/data/elasticsearch/client/util/ScrollState.java

@@ -19,7 +19,7 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.StringUtils;
 
 /**

src/main/java/org/springframework/data/elasticsearch/client/util/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.client.util;

src/main/java/org/springframework/data/elasticsearch/config/ElasticsearchAuditingBeanDefinitionParser.java

@@ -17,6 +17,7 @@ package org.springframework.data.elasticsearch.config;
 
 import static org.springframework.data.config.ParsingUtils.*;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
@@ -28,7 +29,6 @@ import org.springframework.data.auditing.config.IsNewAwareAuditingHandlerBeanDef
 import org.springframework.data.elasticsearch.core.event.AuditingEntityCallback;
 import org.springframework.data.elasticsearch.core.event.ReactiveAuditingEntityCallback;
 import org.springframework.data.elasticsearch.core.mapping.SimpleElasticsearchMappingContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 import org.w3c.dom.Element;

src/main/java/org/springframework/data/elasticsearch/config/ElasticsearchConfigurationSupport.java

@@ -20,6 +20,7 @@ import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
@@ -34,7 +35,6 @@ import org.springframework.data.elasticsearch.core.convert.MappingElasticsearchC
 import org.springframework.data.elasticsearch.core.mapping.SimpleElasticsearchMappingContext;
 import org.springframework.data.mapping.model.FieldNamingStrategy;
 import org.springframework.data.mapping.model.PropertyNameFieldNamingStrategy;
-import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
 

src/main/java/org/springframework/data/elasticsearch/config/package-info.java

@@ -1,3 +1,2 @@
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.config;

src/main/java/org/springframework/data/elasticsearch/core/AbstractElasticsearchTemplate.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import io.micrometer.observation.ObservationRegistry;
+
 import java.time.Duration;
 import java.util.Arrays;
 import java.util.Collections;
@@ -24,6 +26,7 @@ import java.util.Objects;
 import java.util.concurrent.CompletableFuture;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -42,7 +45,6 @@ import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersiste
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
 import org.springframework.data.elasticsearch.core.mapping.SimpleElasticsearchMappingContext;
 import org.springframework.data.elasticsearch.core.query.BulkOptions;
-import org.springframework.data.elasticsearch.core.query.ByQueryResponse;
 import org.springframework.data.elasticsearch.core.query.IndexQuery;
 import org.springframework.data.elasticsearch.core.query.IndexQueryBuilder;
 import org.springframework.data.elasticsearch.core.query.MoreLikeThisQuery;
@@ -57,7 +59,6 @@ import org.springframework.data.elasticsearch.support.VersionInfo;
 import org.springframework.data.mapping.callback.EntityCallbacks;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.util.Streamable;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -85,6 +86,7 @@ public abstract class AbstractElasticsearchTemplate implements ElasticsearchOper
 	@Nullable protected EntityCallbacks entityCallbacks;
 	@Nullable protected RefreshPolicy refreshPolicy;
 	protected RoutingResolver routingResolver;
+	protected ObservationRegistry observationRegistry = ObservationRegistry.NOOP;
 
 	public AbstractElasticsearchTemplate() {
 		this(null);
@@ -117,6 +119,8 @@ public abstract class AbstractElasticsearchTemplate implements ElasticsearchOper
 
 		copy.setRoutingResolver(routingResolver);
 		copy.setRefreshPolicy(refreshPolicy);
+		copy.setObservationRegistry(observationRegistry);
+		customizeCopy(copy);
 
 		return copy;
 	}
@@ -171,6 +175,27 @@ public abstract class AbstractElasticsearchTemplate implements ElasticsearchOper
 		return refreshPolicy;
 	}
 
+	/**
+	 * Set the {@link ObservationRegistry} to use for recording observations.
+	 *
+	 * @param observationRegistry must not be {@literal null}.
+	 * @since 6.1
+	 */
+	public void setObservationRegistry(ObservationRegistry observationRegistry) {
+
+		Assert.notNull(observationRegistry, "observationRegistry must not be null");
+
+		this.observationRegistry = observationRegistry;
+	}
+
+	/**
+	 * Hook for subclasses to copy additional state during {@link #copy()}. Called after all common fields have been
+	 * copied. The default implementation does nothing.
+	 *
+	 * @param copy the new template instance to customize
+	 */
+	protected void customizeCopy(AbstractElasticsearchTemplate copy) {}
+
 	/**
 	 * logs the versions of the different Elasticsearch components.
 	 *

src/main/java/org/springframework/data/elasticsearch/core/AbstractReactiveElasticsearchTemplate.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import io.micrometer.observation.ObservationRegistry;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.publisher.Sinks;
@@ -26,6 +27,7 @@ import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Subscriber;
 import org.reactivestreams.Subscription;
 import org.springframework.beans.BeansException;
@@ -56,7 +58,6 @@ import org.springframework.data.elasticsearch.core.script.Script;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
 import org.springframework.data.elasticsearch.support.VersionInfo;
 import org.springframework.data.mapping.callback.ReactiveEntityCallbacks;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -77,6 +78,7 @@ abstract public class AbstractReactiveElasticsearchTemplate
 	protected RoutingResolver routingResolver;
 
 	protected @Nullable ReactiveEntityCallbacks entityCallbacks;
+	protected ObservationRegistry observationRegistry = ObservationRegistry.NOOP;
 
 	// region Initialization
 	protected AbstractReactiveElasticsearchTemplate(@Nullable ElasticsearchConverter converter) {
@@ -109,6 +111,8 @@ abstract public class AbstractReactiveElasticsearchTemplate
 		}
 
 		copy.setRoutingResolver(routingResolver);
+		copy.setObservationRegistry(observationRegistry);
+		customizeCopy(copy);
 		return copy;
 	}
 
@@ -162,6 +166,27 @@ abstract public class AbstractReactiveElasticsearchTemplate
 		this.entityCallbacks = entityCallbacks;
 	}
 
+	/**
+	 * Set the {@link ObservationRegistry} to use for recording observations.
+	 *
+	 * @param observationRegistry must not be {@literal null}.
+	 * @since 6.1
+	 */
+	public void setObservationRegistry(ObservationRegistry observationRegistry) {
+
+		Assert.notNull(observationRegistry, "observationRegistry must not be null");
+
+		this.observationRegistry = observationRegistry;
+	}
+
+	/**
+	 * Hook for subclasses to copy additional state during {@link #copy()}. Called after all common fields have been
+	 * copied. The default implementation does nothing.
+	 *
+	 * @param copy the new template instance to customize
+	 */
+	protected void customizeCopy(AbstractReactiveElasticsearchTemplate copy) {}
+
 	/**
 	 * logs the versions of the different Elasticsearch components.
 	 *
@@ -259,8 +284,7 @@ abstract public class AbstractReactiveElasticsearchTemplate
 											sink.tryEmitComplete();
 										}
 									})
-									.subscribe(v -> {
-									}, error -> {
+									.subscribe(v -> {}, error -> {
 										if (subscription != null) {
 											subscription.cancel();
 										}

src/main/java/org/springframework/data/elasticsearch/core/DocumentOperations.java

@@ -18,6 +18,7 @@ package org.springframework.data.elasticsearch.core;
 import java.util.Collection;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
 import org.springframework.data.elasticsearch.core.query.BulkOptions;
 import org.springframework.data.elasticsearch.core.query.ByQueryResponse;
@@ -28,7 +29,6 @@ import org.springframework.data.elasticsearch.core.query.UpdateQuery;
 import org.springframework.data.elasticsearch.core.query.UpdateResponse;
 import org.springframework.data.elasticsearch.core.reindex.ReindexRequest;
 import org.springframework.data.elasticsearch.core.reindex.ReindexResponse;
-import org.springframework.lang.Nullable;
 
 /**
  * The operations for the

src/main/java/org/springframework/data/elasticsearch/core/ElasticsearchOperations.java

@@ -15,13 +15,13 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.cluster.ClusterOperations;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
 import org.springframework.data.elasticsearch.core.routing.RoutingResolver;
 import org.springframework.data.elasticsearch.core.script.ScriptOperations;
 import org.springframework.data.elasticsearch.core.sql.SqlOperations;
-import org.springframework.lang.Nullable;
 
 /**
  * ElasticsearchOperations. Since 4.0 this interface only contains common helper functions, the other methods have been

src/main/java/org/springframework/data/elasticsearch/core/EntityOperations.java

@@ -17,6 +17,8 @@ package org.springframework.data.elasticsearch.core;
 
 import java.util.Map;
 
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.data.elasticsearch.core.join.JoinField;
@@ -29,7 +31,6 @@ import org.springframework.data.mapping.IdentifierAccessor;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -123,7 +124,7 @@ public class EntityOperations {
 
 			// Only deal with text because ES generated Ids are strings!
 			if (indexedObjectInformation.id() != null && idProperty != null
-					// isReadable from the base class is false in case of records
+			// isReadable from the base class is false in case of records
 					&& (idProperty.isReadable() || idProperty.getOwner().getType().isRecord())
 					&& idProperty.getType().isAssignableFrom(String.class)) {
 				propertyAccessor.setProperty(idProperty, indexedObjectInformation.id());
@@ -369,7 +370,7 @@ public class EntityOperations {
 		 * @see org.springframework.data.elasticsearch.core.EntityOperations.AdaptableEntity#initializeVersionProperty()
 		 */
 		@Override
-		public T initializeVersionProperty() {
+		public @NonNull T initializeVersionProperty() {
 			return map;
 		}
 
@@ -389,7 +390,7 @@ public class EntityOperations {
 		}
 
 		@Override
-		public SeqNoPrimaryTerm getSeqNoPrimaryTerm() {
+		public @Nullable SeqNoPrimaryTerm getSeqNoPrimaryTerm() {
 			return null;
 		}
 
@@ -398,7 +399,7 @@ public class EntityOperations {
 		 * @see org.springframework.data.elasticsearch.core.EntityOperations.AdaptableEntity#incrementVersion()
 		 */
 		@Override
-		public T incrementVersion() {
+		public @NonNull T incrementVersion() {
 			return map;
 		}
 
@@ -407,7 +408,7 @@ public class EntityOperations {
 		 * @see org.springframework.data.elasticsearch.core.EntityOperations.Entity#getBean()
 		 */
 		@Override
-		public T getBean() {
+		public @NonNull T getBean() {
 			return map;
 		}
 
@@ -425,12 +426,12 @@ public class EntityOperations {
 		 * @see org.springframework.data.elasticsearch.core.EntityOperations.Entity#getPersistentEntity()
 		 */
 		@Override
-		public ElasticsearchPersistentEntity<?> getPersistentEntity() {
+		public @Nullable ElasticsearchPersistentEntity<?> getPersistentEntity() {
 			return null;
 		}
 
 		@Override
-		public String getRouting() {
+		public @Nullable String getRouting() {
 			return null;
 		}
 	}
@@ -650,7 +651,7 @@ public class EntityOperations {
 		}
 
 		@Override
-		public String getRouting() {
+		public @Nullable String getRouting() {
 
 			String routing = routingResolver.getRouting(propertyAccessor.getBean());
 

src/main/java/org/springframework/data/elasticsearch/core/IndexInformation.java

@@ -18,10 +18,10 @@ package org.springframework.data.elasticsearch.core;
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.document.Document;
 import org.springframework.data.elasticsearch.core.index.AliasData;
 import org.springframework.data.elasticsearch.core.index.Settings;
-import org.springframework.lang.Nullable;
 
 /**
  * Immutable object that holds information(name, settings, mappings, aliases) about an Index

src/main/java/org/springframework/data/elasticsearch/core/IndexOperations.java

@@ -19,10 +19,10 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.document.Document;
 import org.springframework.data.elasticsearch.core.index.*;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
-import org.springframework.lang.Nullable;
 
 /**
  * The operations for the

src/main/java/org/springframework/data/elasticsearch/core/IndexOperationsAdapter.java

@@ -22,10 +22,10 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.document.Document;
 import org.springframework.data.elasticsearch.core.index.*;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/core/IndexedObjectInformation.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Value class capturing information about a newly indexed document in Elasticsearch.

src/main/java/org/springframework/data/elasticsearch/core/MultiGetItem.java

@@ -15,8 +15,8 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.ElasticsearchErrorCause;
-import org.springframework.lang.Nullable;
 
 /**
  * Response object for items returned from multiget requests, encapsulating the returned data and potential error

src/main/java/org/springframework/data/elasticsearch/core/ReactiveElasticsearchOperations.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.cluster.ReactiveClusterOperations;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
@@ -22,7 +23,6 @@ import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
 import org.springframework.data.elasticsearch.core.routing.RoutingResolver;
 import org.springframework.data.elasticsearch.core.script.ReactiveScriptOperations;
 import org.springframework.data.elasticsearch.core.sql.ReactiveSqlOperations;
-import org.springframework.lang.Nullable;
 
 /**
  * Interface that specifies a basic set of Elasticsearch operations executed in a reactive way.

src/main/java/org/springframework/data/elasticsearch/core/ReactiveSearchHits.java

@@ -19,8 +19,8 @@ import reactor.core.publisher.Flux;
 
 import java.time.Duration;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
-import org.springframework.lang.Nullable;
 
 /**
  * Encapsulates a Flux of {@link SearchHit}s with additional information from the search.

src/main/java/org/springframework/data/elasticsearch/core/ReactiveSearchHitsImpl.java

@@ -19,8 +19,8 @@ import reactor.core.publisher.Flux;
 
 import java.time.Duration;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
-import org.springframework.lang.Nullable;
 
 /**
  * @author Peter-Josef Meisch

src/main/java/org/springframework/data/elasticsearch/core/SearchHit.java

@@ -23,9 +23,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.document.Explanation;
 import org.springframework.data.elasticsearch.core.document.NestedMetaData;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -48,12 +48,12 @@ public class SearchHit<T> {
 	@Nullable private final NestedMetaData nestedMetaData;
 	@Nullable private final String routing;
 	@Nullable private final Explanation explanation;
-	private final List<String> matchedQueries = new ArrayList<>();
+	private final Map<String, Double> matchedQueries = new LinkedHashMap<>();
 
 	public SearchHit(@Nullable String index, @Nullable String id, @Nullable String routing, float score,
 			@Nullable Object[] sortValues, @Nullable Map<String, List<String>> highlightFields,
 			@Nullable Map<String, SearchHits<?>> innerHits, @Nullable NestedMetaData nestedMetaData,
-			@Nullable Explanation explanation, @Nullable List<String> matchedQueries, T content) {
+			@Nullable Explanation explanation, @Nullable Map<String, Double> matchedQueries, T content) {
 		this.index = index;
 		this.id = id;
 		this.routing = routing;
@@ -73,7 +73,7 @@ public class SearchHit<T> {
 		this.content = content;
 
 		if (matchedQueries != null) {
-			this.matchedQueries.addAll(matchedQueries);
+			this.matchedQueries.putAll(matchedQueries);
 		}
 	}
 
@@ -194,7 +194,7 @@ public class SearchHit<T> {
 	 * @return the matched queries for this SearchHit.
 	 */
 	@Nullable
-	public List<String> getMatchedQueries() {
+	public Map<String, Double> getMatchedQueries() {
 		return matchedQueries;
 	}
 }

src/main/java/org/springframework/data/elasticsearch/core/SearchHitMapping.java

@@ -23,6 +23,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.UncategorizedElasticsearchException;
 import org.springframework.data.elasticsearch.core.convert.ElasticsearchConverter;
 import org.springframework.data.elasticsearch.core.document.Document;
@@ -34,7 +35,6 @@ import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersiste
 import org.springframework.data.elasticsearch.core.suggest.response.CompletionSuggestion;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/core/SearchHitSupport.java

@@ -21,11 +21,12 @@ import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.data.core.ReactiveWrappers;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.util.CloseableIterator;
-import org.springframework.data.util.ReactiveWrappers;
-import org.springframework.lang.Nullable;
 
 /**
  * Utility class with helper methods for working with {@link SearchHit}.

src/main/java/org/springframework/data/elasticsearch/core/SearchHits.java

@@ -19,9 +19,9 @@ import java.time.Duration;
 import java.util.Iterator;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
 import org.springframework.data.util.Streamable;
-import org.springframework.lang.Nullable;
 
 /**
  * Encapsulates a list of {@link SearchHit}s with additional information from the search.

src/main/java/org/springframework/data/elasticsearch/core/SearchHitsImpl.java

@@ -19,9 +19,9 @@ import java.time.Duration;
 import java.util.Collections;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.suggest.response.Suggest;
 import org.springframework.data.util.Lazy;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/core/SearchHitsIterator.java

@@ -17,8 +17,8 @@ package org.springframework.data.elasticsearch.core;
 
 import java.time.Duration;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.util.CloseableIterator;
-import org.springframework.lang.Nullable;
 
 /**
  * A {@link SearchHitsIterator} encapsulates {@link SearchHit} results that can be wrapped in a Java 8

src/main/java/org/springframework/data/elasticsearch/core/SearchOperations.java

@@ -18,11 +18,11 @@ package org.springframework.data.elasticsearch.core;
 import java.time.Duration;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.core.mapping.IndexCoordinates;
 import org.springframework.data.elasticsearch.core.query.BaseQueryBuilder;
 import org.springframework.data.elasticsearch.core.query.MoreLikeThisQuery;
 import org.springframework.data.elasticsearch.core.query.Query;
-import org.springframework.lang.Nullable;
 
 /**
  * The operations for the
@@ -233,7 +233,8 @@ public interface SearchOperations {
 	Query idsQuery(List<String> ids);
 
 	/**
-	 * Creates a {@link BaseQueryBuilder} that has the given ids setto the parameter value. No other properties of the bulder are set.
+	 * Creates a {@link BaseQueryBuilder} that has the given ids setto the parameter value. No other properties of the
+	 * bulder are set.
 	 *
 	 * @param ids the list of ids must not be {@literal null}
 	 * @return query returning the documents with the given ids

src/main/java/org/springframework/data/elasticsearch/core/SearchScrollHits.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * This interface is used to expose the current {@code scrollId} from the underlying scroll context.

src/main/java/org/springframework/data/elasticsearch/core/SearchShardStatistics.java

@@ -17,8 +17,8 @@ package org.springframework.data.elasticsearch.core;
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.ElasticsearchErrorCause;
-import org.springframework.lang.Nullable;
 
 /**
  * @author Haibo Liu

src/main/java/org/springframework/data/elasticsearch/core/StreamQueries.java

@@ -23,8 +23,8 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.elasticsearch.client.util.ScrollState;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/core/cluster/package-info.java

@@ -1,6 +1,5 @@
 /**
  * Interfaces and classes related to Elasticsearch cluster information and management.
  */
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.data.elasticsearch.core.cluster;

src/main/java/org/springframework/data/elasticsearch/core/convert/DefaultElasticsearchTypeMapper.java

@@ -19,15 +19,16 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.data.convert.DefaultTypeMapper;
 import org.springframework.data.convert.SimpleTypeInformationMapper;
 import org.springframework.data.convert.TypeAliasAccessor;
 import org.springframework.data.convert.TypeInformationMapper;
+import org.springframework.data.core.TypeInformation;
 import org.springframework.data.mapping.Alias;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.data.util.TypeInformation;
-import org.springframework.lang.Nullable;
 
 /**
  * Elasticsearch specific {@link org.springframework.data.convert.TypeMapper} implementation.

src/main/java/org/springframework/data/elasticsearch/core/convert/ElasticsearchConverter.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core.convert;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.convert.EntityConverter;
 import org.springframework.data.elasticsearch.core.document.Document;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
@@ -23,7 +24,6 @@ import org.springframework.data.elasticsearch.core.mapping.PropertyValueConverte
 import org.springframework.data.elasticsearch.core.query.Query;
 import org.springframework.data.projection.ProjectionFactory;
 import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

src/main/java/org/springframework/data/elasticsearch/core/convert/ElasticsearchTypeMapper.java

@@ -17,11 +17,11 @@ package org.springframework.data.elasticsearch.core.convert;
 
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.data.convert.TypeMapper;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
 import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentProperty;
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.lang.Nullable;
 
 /**
  * Elasticsearch specific {@link TypeMapper} definition.

src/main/java/org/springframework/data/elasticsearch/core/convert/MappingConversionException.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.data.elasticsearch.core.convert;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * @since 5.3