return auto generated ids

persistence-modules/java-jpa-3/src/main/java/com/baeldung/jpa/IdGeneration/User.java

@@ -0,0 +1,41 @@
+package com.baeldung.jpa.IdGeneration;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+
+@Entity
+public class User {
+
+    @Id
+//    @GeneratedValue(strategy = GenerationType.SEQUENCE)
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private long id;
+    private String username;
+    private String password;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+}

persistence-modules/java-jpa-3/src/main/java/com/baeldung/jpa/IdGeneration/UserService.java

@@ -0,0 +1,19 @@
+package com.baeldung.jpa.IdGeneration;
+
+import javax.persistence.EntityManager;
+import javax.transaction.Transactional;
+
+public class UserService {
+
+    EntityManager entityManager;
+
+    public UserService(EntityManager entityManager) {
+        this.entityManager = entityManager;
+    }
+
+    @Transactional
+    public long saveUser(User user){
+        entityManager.persist(user);
+        return user.getId();
+    }
+}

persistence-modules/java-jpa-3/src/main/resources/META-INF/persistence.xml

@@ -97,4 +97,20 @@
             <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>
         </properties>
     </persistence-unit>
+
+    <persistence-unit name="jpa-h2-id-generation">
+        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
+        <class>com.baeldung.jpa.IdGeneration.User</class>
+        <exclude-unlisted-classes>true</exclude-unlisted-classes>
+        <properties>
+            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
+            <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:idGen"/>
+            <property name="javax.persistence.jdbc.user" value="sa"/>
+            <property name="javax.persistence.jdbc.password" value=""/>
+            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
+            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
+            <property name="hibernate.format_sql" value="true"/>
+            <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>
+        </properties>
+    </persistence-unit>
 </persistence>