Merge remote-tracking branch 'origin/PR-7145' into PR-7145

2023-10-28 21:11:34 +05:30
parent 462ddc7f02 6341e1844f
commit a01a1d720a
226 changed files with 1028 additions and 126 deletions
@@ -0,0 +1,24 @@
+## Axon
+
+This module contains articles about Axon
+
+## Profiles
+
+Optionally the code can be run with the 'mongo' profile to use Mongo to store the projection. Otherwise, an in-memory
+projection is used.
+
+## Scripts
+
+Two scripts are included to easily start middleware using Docker matching the properties files:
+
+- `start_axon_server.sh` to start an Axon Server instance
+- `start_mongo.sh` to start a MongoDB instance
+
+### Relevant articles
+
+- [A Guide to the Axon Framework](https://www.baeldung.com/axon-cqrs-event-sourcing)
+- [Multi-Entity Aggregates in Axon](https://www.baeldung.com/java-axon-multi-entity-aggregates)
+- [Snapshotting Aggregates in Axon](https://www.baeldung.com/axon-snapshotting-aggregates)
+- [Dispatching Queries in Axon Framework](https://www.baeldung.com/axon-query-dispatching)
+- [Persisting the Query Model](https://www.baeldung.com/axon-persisting-query-model)
+- [Using and Testing Axon Applications via REST](https://www.baeldung.com/axon-using-and-testing-rest)
@@ -0,0 +1,119 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>axon</artifactId>
+    <name>axon</name>
+    <description>Basic Axon Framework with Spring Boot configuration tutorial</description>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.axonframework</groupId>
+                <artifactId>axon-bom</artifactId>
+                <version>${axon-bom.version}</version>
+                <type>pom</type>
+                <scope>import</scope>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.axonframework</groupId>
+            <artifactId>axon-spring-boot-starter</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-autoconfigure</artifactId>
+            <scope>compile</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.axonframework.extensions.mongo</groupId>
+            <artifactId>axon-mongo</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.projectreactor</groupId>
+            <artifactId>reactor-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.axonframework</groupId>
+            <artifactId>axon-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.projectreactor</groupId>
+            <artifactId>reactor-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>de.flapdoodle.embed</groupId>
+            <artifactId>de.flapdoodle.embed.mongo</artifactId>
+            <version>${de.flapdoodle.embed.mongo.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-webflux</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.projectreactor.netty</groupId>
+            <artifactId>reactor-netty-http</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>
+                        --add-opens java.base/java.util=ALL-UNNAMED
+                        --add-opens
+                        java.base/java.util.concurrent=ALL-UNNAMED
+                    </argLine>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <axon-bom.version>4.6.3</axon-bom.version>
+        <de.flapdoodle.embed.mongo.version>3.4.8</de.flapdoodle.embed.mongo.version>
+    </properties>
+
+</project>
@@ -0,0 +1,12 @@
+package com.baeldung.axon;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrderApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(OrderApplication.class, args);
+    }
+}
@@ -0,0 +1,17 @@
+package com.baeldung.axon;
+
+import org.axonframework.eventsourcing.EventCountSnapshotTriggerDefinition;
+import org.axonframework.eventsourcing.SnapshotTriggerDefinition;
+import org.axonframework.eventsourcing.Snapshotter;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class OrderApplicationConfiguration {
+
+    @Bean
+    public SnapshotTriggerDefinition orderAggregateSnapshotTriggerDefinition(Snapshotter snapshotter, @Value("${axon.aggregate.order.snapshot-threshold:250}") int threshold) {
+        return new EventCountSnapshotTriggerDefinition(snapshotter, threshold);
+    }
+}
@@ -0,0 +1,99 @@
+package com.baeldung.axon.commandmodel.order;
+
+import com.baeldung.axon.coreapi.commands.AddProductCommand;
+import com.baeldung.axon.coreapi.commands.ConfirmOrderCommand;
+import com.baeldung.axon.coreapi.commands.CreateOrderCommand;
+import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.OrderCreatedEvent;
+import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+import com.baeldung.axon.coreapi.events.ProductAddedEvent;
+import com.baeldung.axon.coreapi.events.ProductRemovedEvent;
+import com.baeldung.axon.coreapi.exceptions.DuplicateOrderLineException;
+import com.baeldung.axon.coreapi.exceptions.OrderAlreadyConfirmedException;
+import com.baeldung.axon.coreapi.exceptions.UnconfirmedOrderException;
+
+import org.axonframework.commandhandling.CommandHandler;
+import org.axonframework.eventsourcing.EventSourcingHandler;
+import org.axonframework.modelling.command.AggregateIdentifier;
+import org.axonframework.modelling.command.AggregateMember;
+import org.axonframework.spring.stereotype.Aggregate;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.axonframework.modelling.command.AggregateLifecycle.apply;
+
+@Aggregate(snapshotTriggerDefinition = "orderAggregateSnapshotTriggerDefinition")
+public class OrderAggregate {
+
+    @AggregateIdentifier
+    private String orderId;
+    private boolean orderConfirmed;
+
+    @AggregateMember
+    private Map<String, OrderLine> orderLines;
+
+    @CommandHandler
+    public OrderAggregate(CreateOrderCommand command) {
+        apply(new OrderCreatedEvent(command.getOrderId()));
+    }
+
+    @CommandHandler
+    public void handle(AddProductCommand command) {
+        if (orderConfirmed) {
+            throw new OrderAlreadyConfirmedException(orderId);
+        }
+
+        String productId = command.getProductId();
+        if (orderLines.containsKey(productId)) {
+            throw new DuplicateOrderLineException(productId);
+        }
+        apply(new ProductAddedEvent(orderId, productId));
+    }
+
+    @CommandHandler
+    public void handle(ConfirmOrderCommand command) {
+        if (orderConfirmed) {
+            return;
+        }
+
+        apply(new OrderConfirmedEvent(orderId));
+    }
+
+    @CommandHandler
+    public void handle(ShipOrderCommand command) {
+        if (!orderConfirmed) {
+            throw new UnconfirmedOrderException();
+        }
+
+        apply(new OrderShippedEvent(orderId));
+    }
+
+    @EventSourcingHandler
+    public void on(OrderCreatedEvent event) {
+        this.orderId = event.getOrderId();
+        this.orderConfirmed = false;
+        this.orderLines = new HashMap<>();
+    }
+
+    @EventSourcingHandler
+    public void on(OrderConfirmedEvent event) {
+        this.orderConfirmed = true;
+    }
+
+    @EventSourcingHandler
+    public void on(ProductAddedEvent event) {
+        String productId = event.getProductId();
+        this.orderLines.put(productId, new OrderLine(productId));
+    }
+
+    @EventSourcingHandler
+    public void on(ProductRemovedEvent event) {
+        this.orderLines.remove(event.getProductId());
+    }
+
+    protected OrderAggregate() {
+        // Required by Axon to build a default Aggregate prior to Event Sourcing
+    }
+}
@@ -0,0 +1,84 @@
+package com.baeldung.axon.commandmodel.order;
+
+import com.baeldung.axon.coreapi.commands.DecrementProductCountCommand;
+import com.baeldung.axon.coreapi.commands.IncrementProductCountCommand;
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.ProductCountDecrementedEvent;
+import com.baeldung.axon.coreapi.events.ProductCountIncrementedEvent;
+import com.baeldung.axon.coreapi.events.ProductRemovedEvent;
+import com.baeldung.axon.coreapi.exceptions.OrderAlreadyConfirmedException;
+
+import org.axonframework.commandhandling.CommandHandler;
+import org.axonframework.eventsourcing.EventSourcingHandler;
+import org.axonframework.modelling.command.EntityId;
+
+import java.util.Objects;
+
+import static org.axonframework.modelling.command.AggregateLifecycle.apply;
+
+public class OrderLine {
+
+    @EntityId
+    private final String productId;
+    private Integer count;
+    private boolean orderConfirmed;
+
+    public OrderLine(String productId) {
+        this.productId = productId;
+        this.count = 1;
+    }
+
+    @CommandHandler
+    public void handle(IncrementProductCountCommand command) {
+        if (orderConfirmed) {
+            throw new OrderAlreadyConfirmedException(command.getOrderId());
+        }
+
+        apply(new ProductCountIncrementedEvent(command.getOrderId(), productId));
+    }
+
+    @CommandHandler
+    public void handle(DecrementProductCountCommand command) {
+        if (orderConfirmed) {
+            throw new OrderAlreadyConfirmedException(command.getOrderId());
+        }
+
+        if (count <= 1) {
+            apply(new ProductRemovedEvent(command.getOrderId(), productId));
+        } else {
+            apply(new ProductCountDecrementedEvent(command.getOrderId(), productId));
+        }
+    }
+
+    @EventSourcingHandler
+    public void on(ProductCountIncrementedEvent event) {
+        this.count++;
+    }
+
+    @EventSourcingHandler
+    public void on(ProductCountDecrementedEvent event) {
+        this.count--;
+    }
+
+    @EventSourcingHandler
+    public void on(OrderConfirmedEvent event) {
+        this.orderConfirmed = true;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        OrderLine orderLine = (OrderLine) o;
+        return Objects.equals(productId, orderLine.productId) && Objects.equals(count, orderLine.count);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(productId, count);
+    }
+}
@@ -0,0 +1,47 @@
+package com.baeldung.axon.coreapi.commands;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+import java.util.Objects;
+
+public class AddProductCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+    private final String productId;
+
+    public AddProductCommand(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        AddProductCommand that = (AddProductCommand) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "AddProductCommand{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,41 @@
+package com.baeldung.axon.coreapi.commands;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+import java.util.Objects;
+
+public class ConfirmOrderCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+
+    public ConfirmOrderCommand(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final ConfirmOrderCommand other = (ConfirmOrderCommand) obj;
+        return Objects.equals(this.orderId, other.orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "ConfirmOrderCommand{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,41 @@
+package com.baeldung.axon.coreapi.commands;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+import java.util.Objects;
+
+public class CreateOrderCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+
+    public CreateOrderCommand(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        CreateOrderCommand that = (CreateOrderCommand) o;
+        return Objects.equals(orderId, that.orderId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "CreateOrderCommand{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,47 @@
+package com.baeldung.axon.coreapi.commands;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+import java.util.Objects;
+
+public class DecrementProductCountCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+    private final String productId;
+
+    public DecrementProductCountCommand(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        DecrementProductCountCommand that = (DecrementProductCountCommand) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "DecrementProductCountCommand{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,47 @@
+package com.baeldung.axon.coreapi.commands;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+import java.util.Objects;
+
+public class IncrementProductCountCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+    private final String productId;
+
+    public IncrementProductCountCommand(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        IncrementProductCountCommand that = (IncrementProductCountCommand) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "IncrementProductCountCommand{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,41 @@
+package com.baeldung.axon.coreapi.commands;
+
+import java.util.Objects;
+
+import org.axonframework.modelling.command.TargetAggregateIdentifier;
+
+public class ShipOrderCommand {
+
+    @TargetAggregateIdentifier
+    private final String orderId;
+
+    public ShipOrderCommand(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final ShipOrderCommand other = (ShipOrderCommand) obj;
+        return Objects.equals(this.orderId, other.orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "ShipOrderCommand{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,38 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class OrderConfirmedEvent {
+
+    private final String orderId;
+
+    public OrderConfirmedEvent(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final OrderConfirmedEvent other = (OrderConfirmedEvent) obj;
+        return Objects.equals(this.orderId, other.orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "OrderConfirmedEvent{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,38 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class OrderCreatedEvent {
+
+    private final String orderId;
+
+    public OrderCreatedEvent(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        OrderCreatedEvent that = (OrderCreatedEvent) o;
+        return Objects.equals(orderId, that.orderId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "OrderCreatedEvent{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,38 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class OrderShippedEvent {
+
+    private final String orderId;
+
+    public OrderShippedEvent(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final OrderShippedEvent other = (OrderShippedEvent) obj;
+        return Objects.equals(this.orderId, other.orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "OrderShippedEvent{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class ProductAddedEvent {
+
+    private final String orderId;
+    private final String productId;
+
+    public ProductAddedEvent(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        ProductAddedEvent that = (ProductAddedEvent) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "ProductAddedEvent{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class ProductCountDecrementedEvent {
+
+    private final String orderId;
+    private final String productId;
+
+    public ProductCountDecrementedEvent(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        ProductCountDecrementedEvent that = (ProductCountDecrementedEvent) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "ProductCountDecrementedEvent{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class ProductCountIncrementedEvent {
+
+    private final String orderId;
+    private final String productId;
+
+    public ProductCountIncrementedEvent(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        ProductCountIncrementedEvent that = (ProductCountIncrementedEvent) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "ProductCountIncrementedEvent{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.axon.coreapi.events;
+
+import java.util.Objects;
+
+public class ProductRemovedEvent {
+
+    private final String orderId;
+    private final String productId;
+
+    public ProductRemovedEvent(String orderId, String productId) {
+        this.orderId = orderId;
+        this.productId = productId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        ProductRemovedEvent that = (ProductRemovedEvent) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, productId);
+    }
+
+    @Override
+    public String toString() {
+        return "ProductRemovedEvent{" + "orderId='" + orderId + '\'' + ", productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,8 @@
+package com.baeldung.axon.coreapi.exceptions;
+
+public class DuplicateOrderLineException extends IllegalStateException {
+
+    public DuplicateOrderLineException(String productId) {
+        super("Cannot duplicate order line for product identifier [" + productId + "]");
+    }
+}
@@ -0,0 +1,8 @@
+package com.baeldung.axon.coreapi.exceptions;
+
+public class OrderAlreadyConfirmedException extends IllegalStateException {
+
+    public OrderAlreadyConfirmedException(String orderId) {
+        super("Cannot perform operation because order [" + orderId + "] is already confirmed.");
+    }
+}
@@ -0,0 +1,8 @@
+package com.baeldung.axon.coreapi.exceptions;
+
+public class UnconfirmedOrderException extends IllegalStateException {
+
+    public UnconfirmedOrderException() {
+        super("Cannot ship an order which has not been confirmed yet.");
+    }
+}
@@ -0,0 +1,5 @@
+package com.baeldung.axon.coreapi.queries;
+
+public class FindAllOrderedProductsQuery {
+
+}
@@ -0,0 +1,76 @@
+package com.baeldung.axon.coreapi.queries;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+public class Order {
+
+    private final String orderId;
+    private final Map<String, Integer> products;
+    private OrderStatus orderStatus;
+
+    public Order(String orderId) {
+        this.orderId = orderId;
+        this.products = new HashMap<>();
+        orderStatus = OrderStatus.CREATED;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public Map<String, Integer> getProducts() {
+        return products;
+    }
+
+    public OrderStatus getOrderStatus() {
+        return orderStatus;
+    }
+
+    public void addProduct(String productId) {
+        products.putIfAbsent(productId, 1);
+    }
+
+    public void incrementProductInstance(String productId) {
+        products.computeIfPresent(productId, (id, count) -> ++count);
+    }
+
+    public void decrementProductInstance(String productId) {
+        products.computeIfPresent(productId, (id, count) -> --count);
+    }
+
+    public void removeProduct(String productId) {
+        products.remove(productId);
+    }
+
+    public void setOrderConfirmed() {
+        this.orderStatus = OrderStatus.CONFIRMED;
+    }
+
+    public void setOrderShipped() {
+        this.orderStatus = OrderStatus.SHIPPED;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Order that = (Order) o;
+        return Objects.equals(orderId, that.orderId) && Objects.equals(products, that.products) && orderStatus == that.orderStatus;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId, products, orderStatus);
+    }
+
+    @Override
+    public String toString() {
+        return "Order{" + "orderId='" + orderId + '\'' + ", products=" + products + ", orderStatus=" + orderStatus + '}';
+    }
+}
@@ -0,0 +1,6 @@
+package com.baeldung.axon.coreapi.queries;
+
+public enum OrderStatus {
+
+    CREATED, CONFIRMED, SHIPPED
+}
@@ -0,0 +1,37 @@
+package com.baeldung.axon.coreapi.queries;
+
+import java.util.Objects;
+
+public class OrderUpdatesQuery {
+
+    private final String orderId;
+
+    public OrderUpdatesQuery(String orderId) {
+        this.orderId = orderId;
+    }
+
+    public String getOrderId() {
+        return orderId;
+    }
+
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        OrderUpdatesQuery that = (OrderUpdatesQuery) o;
+        return Objects.equals(orderId, that.orderId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(orderId);
+    }
+
+    @Override
+    public String toString() {
+        return "OrderUpdatesQuery{" + "orderId='" + orderId + '\'' + '}';
+    }
+}
@@ -0,0 +1,37 @@
+package com.baeldung.axon.coreapi.queries;
+
+import java.util.Objects;
+
+public class TotalProductsShippedQuery {
+
+    private final String productId;
+
+    public TotalProductsShippedQuery(String productId) {
+        this.productId = productId;
+    }
+
+    public String getProductId() {
+        return productId;
+    }
+
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        TotalProductsShippedQuery that = (TotalProductsShippedQuery) o;
+        return Objects.equals(productId, that.productId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(productId);
+    }
+
+    @Override
+    public String toString() {
+        return "TotalProductsShippedQuery{" + "productId='" + productId + '\'' + '}';
+    }
+}
@@ -0,0 +1,111 @@
+package com.baeldung.axon.gui;
+
+import com.baeldung.axon.coreapi.commands.AddProductCommand;
+import com.baeldung.axon.coreapi.commands.ConfirmOrderCommand;
+import com.baeldung.axon.coreapi.commands.CreateOrderCommand;
+import com.baeldung.axon.coreapi.commands.DecrementProductCountCommand;
+import com.baeldung.axon.coreapi.commands.IncrementProductCountCommand;
+import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
+import com.baeldung.axon.querymodel.OrderQueryService;
+import com.baeldung.axon.querymodel.OrderResponse;
+
+import org.axonframework.commandhandling.gateway.CommandGateway;
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import reactor.core.publisher.Flux;
+
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+
+@RestController
+public class OrderRestEndpoint {
+
+    private final CommandGateway commandGateway;
+    private final OrderQueryService orderQueryService;
+
+    public OrderRestEndpoint(CommandGateway commandGateway, OrderQueryService orderQueryService) {
+        this.commandGateway = commandGateway;
+        this.orderQueryService = orderQueryService;
+    }
+
+    @PostMapping("/ship-order")
+    public CompletableFuture<Void> shipOrder() {
+        String orderId = UUID.randomUUID()
+          .toString();
+        return commandGateway.send(new CreateOrderCommand(orderId))
+          .thenCompose(result -> commandGateway.send(new AddProductCommand(orderId, "Deluxe Chair")))
+          .thenCompose(result -> commandGateway.send(new ConfirmOrderCommand(orderId)))
+          .thenCompose(result -> commandGateway.send(new ShipOrderCommand(orderId)));
+    }
+
+    @PostMapping("/ship-unconfirmed-order")
+    public CompletableFuture<Void> shipUnconfirmedOrder() {
+        String orderId = UUID.randomUUID()
+          .toString();
+        return commandGateway.send(new CreateOrderCommand(orderId))
+          .thenCompose(result -> commandGateway.send(new AddProductCommand(orderId, "Deluxe Chair")))
+          // This throws an exception, as an Order cannot be shipped if it has not been confirmed yet.
+          .thenCompose(result -> commandGateway.send(new ShipOrderCommand(orderId)));
+    }
+
+    @PostMapping("/order")
+    public CompletableFuture<String> createOrder() {
+        return createOrder(UUID.randomUUID()
+          .toString());
+    }
+
+    @PostMapping("/order/{order-id}")
+    public CompletableFuture<String> createOrder(@PathVariable("order-id") String orderId) {
+        return commandGateway.send(new CreateOrderCommand(orderId));
+    }
+
+    @PostMapping("/order/{order-id}/product/{product-id}")
+    public CompletableFuture<Void> addProduct(@PathVariable("order-id") String orderId, @PathVariable("product-id") String productId) {
+        return commandGateway.send(new AddProductCommand(orderId, productId));
+    }
+
+    @PostMapping("/order/{order-id}/product/{product-id}/increment")
+    public CompletableFuture<Void> incrementProduct(@PathVariable("order-id") String orderId, @PathVariable("product-id") String productId) {
+        return commandGateway.send(new IncrementProductCountCommand(orderId, productId));
+    }
+
+    @PostMapping("/order/{order-id}/product/{product-id}/decrement")
+    public CompletableFuture<Void> decrementProduct(@PathVariable("order-id") String orderId, @PathVariable("product-id") String productId) {
+        return commandGateway.send(new DecrementProductCountCommand(orderId, productId));
+    }
+
+    @PostMapping("/order/{order-id}/confirm")
+    public CompletableFuture<Void> confirmOrder(@PathVariable("order-id") String orderId) {
+        return commandGateway.send(new ConfirmOrderCommand(orderId));
+    }
+
+    @PostMapping("/order/{order-id}/ship")
+    public CompletableFuture<Void> shipOrder(@PathVariable("order-id") String orderId) {
+        return commandGateway.send(new ShipOrderCommand(orderId));
+    }
+
+    @GetMapping("/all-orders")
+    public CompletableFuture<List<OrderResponse>> findAllOrders() {
+        return orderQueryService.findAllOrders();
+    }
+
+    @GetMapping(path = "/all-orders-streaming", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
+    public Flux<OrderResponse> allOrdersStreaming() {
+        return orderQueryService.allOrdersStreaming();
+    }
+
+    @GetMapping("/total-shipped/{product-id}")
+    public Integer totalShipped(@PathVariable("product-id") String productId) {
+        return orderQueryService.totalShipped(productId);
+    }
+
+    @GetMapping(path = "/order-updates/{order-id}", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
+    public Flux<OrderResponse> orderUpdates(@PathVariable("order-id") String orderId) {
+        return orderQueryService.orderUpdates(orderId);
+    }
+}
@@ -0,0 +1,142 @@
+package com.baeldung.axon.querymodel;
+
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.OrderCreatedEvent;
+import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+import com.baeldung.axon.coreapi.events.ProductAddedEvent;
+import com.baeldung.axon.coreapi.events.ProductCountDecrementedEvent;
+import com.baeldung.axon.coreapi.events.ProductCountIncrementedEvent;
+import com.baeldung.axon.coreapi.events.ProductRemovedEvent;
+import com.baeldung.axon.coreapi.queries.FindAllOrderedProductsQuery;
+import com.baeldung.axon.coreapi.queries.Order;
+import com.baeldung.axon.coreapi.queries.OrderStatus;
+import com.baeldung.axon.coreapi.queries.OrderUpdatesQuery;
+import com.baeldung.axon.coreapi.queries.TotalProductsShippedQuery;
+
+import org.axonframework.config.ProcessingGroup;
+import org.axonframework.eventhandling.EventHandler;
+import org.axonframework.queryhandling.QueryHandler;
+import org.axonframework.queryhandling.QueryUpdateEmitter;
+import org.reactivestreams.Publisher;
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+@Service
+@ProcessingGroup("orders")
+@Profile("!mongo")
+public class InMemoryOrdersEventHandler implements OrdersEventHandler {
+
+    private final Map<String, Order> orders = new HashMap<>();
+    private final QueryUpdateEmitter emitter;
+
+    public InMemoryOrdersEventHandler(QueryUpdateEmitter emitter) {
+        this.emitter = emitter;
+    }
+
+    @EventHandler
+    public void on(OrderCreatedEvent event) {
+        String orderId = event.getOrderId();
+        orders.put(orderId, new Order(orderId));
+    }
+
+    @EventHandler
+    public void on(ProductAddedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.addProduct(event.getProductId());
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @EventHandler
+    public void on(ProductCountIncrementedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.incrementProductInstance(event.getProductId());
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @EventHandler
+    public void on(ProductCountDecrementedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.decrementProductInstance(event.getProductId());
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @EventHandler
+    public void on(ProductRemovedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.removeProduct(event.getProductId());
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @EventHandler
+    public void on(OrderConfirmedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.setOrderConfirmed();
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @EventHandler
+    public void on(OrderShippedEvent event) {
+        orders.computeIfPresent(event.getOrderId(), (orderId, order) -> {
+            order.setOrderShipped();
+            emitUpdate(order);
+            return order;
+        });
+    }
+
+    @QueryHandler
+    public List<Order> handle(FindAllOrderedProductsQuery query) {
+        return new ArrayList<>(orders.values());
+    }
+
+    @QueryHandler
+    public Publisher<Order> handleStreaming(FindAllOrderedProductsQuery query) {
+        return Mono.fromCallable(orders::values)
+          .flatMapMany(Flux::fromIterable);
+    }
+
+    @QueryHandler
+    public Integer handle(TotalProductsShippedQuery query) {
+        return orders.values()
+          .stream()
+          .filter(o -> o.getOrderStatus() == OrderStatus.SHIPPED)
+          .map(o -> Optional.ofNullable(o.getProducts()
+              .get(query.getProductId()))
+            .orElse(0))
+          .reduce(0, Integer::sum);
+    }
+
+    @QueryHandler
+    public Order handle(OrderUpdatesQuery query) {
+        return orders.get(query.getOrderId());
+    }
+
+    private void emitUpdate(Order order) {
+        emitter.emit(OrderUpdatesQuery.class, q -> order.getOrderId()
+          .equals(q.getOrderId()), order);
+    }
+
+    @Override
+    public void reset(List<Order> orderList) {
+        orders.clear();
+        orderList.forEach(o -> orders.put(o.getOrderId(), o));
+    }
+}
@@ -0,0 +1,22 @@
+package com.baeldung.axon.querymodel;
+
+import com.baeldung.axon.coreapi.queries.TotalProductsShippedQuery;
+
+import org.axonframework.queryhandling.QueryHandler;
+import org.springframework.stereotype.Service;
+
+@Service
+public class LegacyQueryHandler {
+
+    @QueryHandler
+    public Integer handle(TotalProductsShippedQuery query) {
+        switch (query.getProductId()) {
+        case "Deluxe Chair":
+            return 234;
+        case "a6aa01eb-4e38-4dfb-b53b-b5b82961fbf3":
+            return 10;
+        default:
+            return 0;
+        }
+    }
+}
--- a/Show More
+++ b/Show More