Demonstrating use of composite ids.

jdbc/composite-ids/README.adoc

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+== Spring Data JDBC Composite Id
+
+=== EmployeeTest
+
+Demonstrates saving an entity with composite id.
+
+Once by using a direct insert, via a custom `insert` method in the repository, backed by `JdbcAggregateTemplate.insert` and once by a custom id generating callback.
+See `CompositeConfiguration.idGeneration()`.

jdbc/composite-ids/pom.xml

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+<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 https://maven.apache.org/maven-v4_0_0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>spring-data-jdbc-composite-ids</artifactId>
+
+	<parent>
+		<groupId>org.springframework.data.examples</groupId>
+		<artifactId>spring-data-jdbc-examples</artifactId>
+		<version>2.0.0.BUILD-SNAPSHOT</version>
+		<relativePath>../pom.xml</relativePath>
+	</parent>
+
+	<name>Spring Data JDBC - Examples using composite ids</name>
+	<description>Sample project demonstrating Spring Data JDBCs support for custom ids</description>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.data</groupId>
+			<artifactId>spring-data-jdbc</artifactId>
+			<version>4.0.0-SNAPSHOT</version>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.data</groupId>
+			<artifactId>spring-data-relational</artifactId>
+			<version>4.0.0-SNAPSHOT</version>
+		</dependency>
+	</dependencies>
+
+</project>

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/CompositeConfiguration.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.jdbc.repository.config.AbstractJdbcConfiguration;
+import org.springframework.data.jdbc.repository.config.EnableJdbcRepositories;
+import org.springframework.data.relational.core.mapping.event.BeforeConvertCallback;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+
+/**
+ * Configuration for the demonstration of composite ids.
+ *
+ * Registers a {@link BeforeConvertCallback} for generating ids.
+ *
+ * @author Jens Schauder
+ */
+@Configuration
+@EnableJdbcRepositories
+public class CompositeConfiguration extends AbstractJdbcConfiguration {
+
+	@Bean
+	BeforeConvertCallback<Employee> idGeneration() {
+		return new BeforeConvertCallback<>() {
+			AtomicLong counter = new AtomicLong();
+
+			@Override
+			public Employee onBeforeConvert(Employee employee) {
+				if (employee.id == null) {
+					employee.id = new EmployeeId(Organization.RND, counter.addAndGet(1));
+				}
+				return employee;
+			}
+		};
+	}
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/Employee.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.PersistenceCreator;
+
+/**
+ * A simple entity sporting a compostite id.
+ *
+ * @author Jens Schauder
+ */
+class Employee {
+
+	@Id
+	EmployeeId id;
+
+	String name;
+
+	@PersistenceCreator
+	Employee(EmployeeId id, String name) {
+
+		this.id = id;
+		this.name = name;
+	}
+
+	Employee(String name) {
+		this.name = name;
+	}
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/EmployeeId.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+/**
+ * Composite id for {@link Employee} instances.
+ *
+ * @author Jens Schauder
+ */
+record EmployeeId(
+		Organization organization,
+		Long employeeNumber) {
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/EmployeeRepository.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+import org.springframework.data.repository.ListCrudRepository;
+
+
+/**
+ * Repositories for {@link Employee} instances.
+ *
+ * @author Jens Schauder
+ * @see InsertRepository
+ * @see InsertRepositoryImpl
+ */
+interface EmployeeRepository extends ListCrudRepository<Employee, EmployeeId>, InsertRepository<Employee> {
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/InsertRepository.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+
+/**
+ * Interface for repositories supporting an {@literal insert} operation, that always performs an insert on the database
+ * and does not check the instance.
+ *
+ * @author Jens Schauder
+ */
+interface InsertRepository<E> {
+	E insert(E employee);
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/InsertRepositoryImpl.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.jdbc.core.JdbcAggregateTemplate;
+
+/**
+ * Fragment implementing the {@literal insert} operation using a {@link JdbcAggregateTemplate}.
+ *
+ * @author Jens Schauder
+ */
+class InsertRepositoryImpl<E> implements InsertRepository<E> {
+	@Autowired
+	private JdbcAggregateTemplate template;
+	@Override
+	public E insert(E employee) {
+		return template.insert(employee);
+	}
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/Organization.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+/**
+ * Just an enum to be part of the composite id, to demonstrate that one may use various datatypes.
+ *
+ * @author Jens Schauder
+ */
+enum Organization {
+	RND,
+	SALES,
+	MARKETING,
+	PURCHASING
+}

jdbc/composite-ids/src/main/java/example/springdata/jdbc/compositeid/package-info.java

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+@NonNullApi
+package example.springdata.jdbc.compositeid;
+
+import org.springframework.lang.NonNullApi;

jdbc/composite-ids/src/main/resources/application.properties

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+logging.level.org.springframework.data=INFO
+logging.level.org.springframework.jdbc.core.JdbcTemplate=DEBUG

jdbc/composite-ids/src/main/resources/schema.sql

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+create table employee
+(
+    organization    varchar(20),
+    employee_number int,
+    name            varchar(100)
+);

jdbc/composite-ids/src/test/java/example/springdata/jdbc/compositeid/EmployeeTests.java

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+/*
+ * Copyright 2025 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 example.springdata.jdbc.compositeid;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.data.jdbc.AutoConfigureDataJdbc;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import static org.assertj.core.api.Assertions.*;
+
+/**
+ * Test demonstrating the use of composite ids.
+ *
+ * @author Jens Schauder
+ */
+@SpringBootTest(classes = CompositeConfiguration.class)
+@AutoConfigureDataJdbc
+class EmployeeTests {
+
+	@Autowired
+	EmployeeRepository repository;
+
+	@Test
+	void employeeDirectInsert() {
+
+		Employee employee = repository.insert(new Employee(new EmployeeId(Organization.RND, 23L), "Jens Schauder"));
+
+		Employee reloaded = repository.findById(employee.id).orElseThrow();
+
+		assertThat(reloaded.name).isEqualTo(employee.name);
+	}
+
+	@Test
+	void employeeIdGeneration() {
+
+		Employee employee = repository.save(new Employee("Mark Paluch"));
+
+		assertThat(employee.id).isNotNull();
+	}
+}

jdbc/pom.xml

@@ -18,6 +18,7 @@
 
 	<modules>
 		<module>basics</module>
+		<module>composite-ids</module>
 		<module>howto</module>
 		<module>immutables</module>
 		<module>jmolecules</module>