Spring Data JPA

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Entity with Auditing

@Entity
@Table(name = "users")
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
@EntityListeners(AuditingEntityListener.class)
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, length = 100)
    private String name;

    @Column(unique = true, nullable = false)
    private String email;

    @Enumerated(EnumType.STRING)
    @Column(nullable = false)
    private UserRole role = UserRole.USER;

    @Enumerated(EnumType.STRING)
    @Column(nullable = false)
    private UserStatus status = UserStatus.ACTIVE;

    @CreatedDate
    @Column(updatable = false)
    private LocalDateTime createdAt;

    @LastModifiedDate
    private LocalDateTime updatedAt;

    @CreatedBy
    @Column(updatable = false)
    private String createdBy;

    @LastModifiedBy
    private String updatedBy;
}

Repository Interface

@Repository
public interface UserRepository extends JpaRepository<User, Long> {

    // Derived query methods
    Optional<User> findByEmail(String email);
    boolean existsByEmail(String email);
    List<User> findByStatus(UserStatus status);
    List<User> findByRoleIn(List<UserRole> roles);

    // Query with JPQL
    @Query("SELECT u FROM User u WHERE u.status = :status AND u.role = :role")
    List<User> findByStatusAndRole(
        @Param("status") UserStatus status,
        @Param("role") UserRole role
    );

    // Native query
    @Query(value = "SELECT * FROM users WHERE email LIKE %:domain", nativeQuery = true)
    List<User> findByEmailDomain(@Param("domain") String domain);

    // Pagination
    Page<User> findByNameContainingIgnoreCase(String name, Pageable pageable);

    // Sorting
    List<User> findByStatus(UserStatus status, Sort sort);

    // Modifying queries
    @Modifying
    @Query("UPDATE User u SET u.status = :status WHERE u.id = :id")
    int updateStatus(@Param("id") Long id, @Param("status") UserStatus status);

    @Modifying
    @Query("DELETE FROM User u WHERE u.status = :status")
    int deleteByStatus(@Param("status") UserStatus status);
}

Relationships

// One-to-Many
@Entity
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = "department", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Employee> employees = new ArrayList<>();
}

@Entity
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "department_id", nullable = false)
    private Department department;
}

// Many-to-Many
@Entity
public class User {
    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(
        name = "user_roles",
        joinColumns = @JoinColumn(name = "user_id"),
        inverseJoinColumns = @JoinColumn(name = "role_id")
    )
    private Set<Role> roles = new HashSet<>();
}

Pagination & Sorting

@Service
public class UserService {

    public Page<UserResponse> findAll(int page, int size, String sortBy, String direction) {
        Sort sort = Sort.by(Sort.Direction.fromString(direction), sortBy);
        Pageable pageable = PageRequest.of(page, size, sort);
        return userRepository.findAll(pageable)
            .map(userMapper::toResponse);
    }

    public Page<UserResponse> search(String query, Pageable pageable) {
        return userRepository.findByNameContainingIgnoreCase(query, pageable)
            .map(userMapper::toResponse);
    }
}

// Controller
@GetMapping
public ResponseEntity<Page<UserResponse>> findAll(
        @RequestParam(defaultValue = "0") int page,
        @RequestParam(defaultValue = "10") int size,
        @RequestParam(defaultValue = "createdAt") String sortBy,
        @RequestParam(defaultValue = "desc") String direction) {
    return ResponseEntity.ok(userService.findAll(page, size, sortBy, direction));
}

Specifications (Dynamic Queries)

public class UserSpecifications {

    public static Specification<User> hasStatus(UserStatus status) {
        return (root, query, cb) ->
            status == null ? null : cb.equal(root.get("status"), status);
    }

    public static Specification<User> hasRole(UserRole role) {
        return (root, query, cb) ->
            role == null ? null : cb.equal(root.get("role"), role);
    }

    public static Specification<User> nameContains(String name) {
        return (root, query, cb) ->
            name == null ? null : cb.like(cb.lower(root.get("name")),
                "%" + name.toLowerCase() + "%");
    }
}

// Repository extends JpaSpecificationExecutor
public interface UserRepository extends
        JpaRepository<User, Long>,
        JpaSpecificationExecutor<User> {}

// Usage
Specification<User> spec = Specification
    .where(UserSpecifications.hasStatus(UserStatus.ACTIVE))
    .and(UserSpecifications.hasRole(UserRole.ADMIN))
    .and(UserSpecifications.nameContains("john"));

List<User> users = userRepository.findAll(spec);

Enable Auditing

@Configuration
@EnableJpaAuditing
public class JpaConfig {

    @Bean
    public AuditorAware<String> auditorProvider() {
        return () -> Optional.ofNullable(SecurityContextHolder.getContext())
            .map(SecurityContext::getAuthentication)
            .filter(Authentication::isAuthenticated)
            .map(Authentication::getName);
    }
}

Key Annotations

When NOT to Use This Skill

• Spring Boot application setup → Use spring-boot skill
• REST API patterns → Use spring-web skill
• MongoDB operations → Use mongodb-expert skill
• Security configuration → Use spring-security skill
• Raw SQL optimization → Use sql-expert skill
• Reactive database access → Use spring-r2dbc skill

Anti-Patterns

Quick Troubleshooting

Reference Documentation

• Spring Data JPA Reference
• Query Methods
• Specifications