Using JPA Entity Graph with H2 Database in Spring Boot

October 29, 2025

#1

This guide explains how to use JPA Entity Graph in Spring Boot with H2 to optimize queries and avoid unnecessary lazy loading.

1. Add Dependencies

In pom.xml:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
  <groupId>com.h2database</groupId>
  <artifactId>h2</artifactId>
</dependency>

2. Configure H2

In application.properties:

spring.datasource.url=jdbc:h2:mem:entitydb
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.hibernate.ddl-auto=create
spring.h2.console.enabled=true

3. Define Entities

Employee and Department:

@Entity
public class Department {
  @Id @GeneratedValue
  private Long id;
  private String name;
}

@Entity
public class Employee {
  @Id @GeneratedValue
  private Long id;
  private String name;

  @ManyToOne(fetch = FetchType.LAZY)
  private Department department;
}

4. Repository with Entity Graph

public interface EmployeeRepository extends JpaRepository<Employee, Long> {
  
  @EntityGraph(attributePaths = "department")
  List<Employee> findAll();
}

Here, the department is eagerly fetched using an entity graph.

5. Test Query

@SpringBootTest
class EmployeeRepoTest {
  @Autowired EmployeeRepository repo;

  @Test
  void testFindAllWithGraph() {
    repo.findAll().forEach(e -> System.out.println(e.getDepartment().getName()));
  }
}

No lazy initialization exception will occur since department is fetched eagerly.