spring-data-jpa

Spring Data JPA

Overview

Provides patterns for Spring Data JPA repositories, entity relationships, queries, pagination, auditing, and transactions.

When to Use

Creating repositories with CRUD operations, entity relationships, @Query annotations, pagination, auditing, or UUID primary keys.

Instructions

Create Repository Interfaces

To implement a repository interface:

1. Extend the appropriate repository interface:

   @Repository
   public interface UserRepository extends JpaRepository<User, Long> {
       // Custom methods defined here
   }
   

2. Use derived queries for simple conditions:

   Optional<User> findByEmail(String email);
   List<User> findByStatusOrderByCreatedDateDesc(String status);
   

3. Implement custom queries with @Query:

   @Query("SELECT u FROM User u WHERE u.status = :status")
   List<User> findActiveUsers(@Param("status") String status);
   

Configure Entities

1. Define entities with proper annotations:

   @Entity
   @Table(name = "users")
   public class User {
       @Id
       @GeneratedValue(strategy = GenerationType.IDENTITY)
       private Long id;
   
       @Column(nullable = false, length = 100)
       private String email;
   }
   

2. Configure relationships using appropriate cascade types:

   @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
   private List<Order> orders = new ArrayList<>();
   

   Validation: Test cascade behavior with a small dataset before applying to production data. Verify delete operations don't cascade unexpectedly.

3. Set up database auditing:

   @CreatedDate
   @Column(nullable = false, updatable = false)
   private LocalDateTime createdDate;
   

Apply Query Patterns

1. Use derived queries for simple conditions
2. Use @Query for complex queries
3. Return Optional for single results
4. Use Pageable for pagination
5. Apply @Modifying for update/delete operations