java-crud-pattern

name	java-crud-pattern
description	How to create a new CRUD module (Entity → DTO → Mapper → Repository → Service → Controller REST)

Steps to create a new CRUD module

1. Entity (entity/)

@Entity
@Table(name = "table_name")
public class XxxEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    // fields with @Column
}

2. DTOs (dto/)

• XxxRequestDto.java with @Data (Lombok) for input
• XxxResponseDto.java as record for output

3. Mapper (mapper/)

@Component
public class XxxMapper extends MapperDTO<XxxResponseDto, XxxEntity> {
    @Override
    public XxxResponseDto toDTO(XxxEntity entity) { ... }
}

4. Repository (dao/)

public interface XxxRepository extends JpaRepository<XxxEntity, Integer> {
    // custom @Query methods if needed
}

5. Service (services/)

Inject the repository and mapper. Use mapper.toDTO() and mapper.toDTOList() — never manual mapping.

6. Controller REST (controllers/rest/)

@RestController
@RequestMapping("/api/xxx")
public class XxxController {
    @Autowired private XxxService xxxService;
    @Autowired private AuthService authService;
    @Autowired private UserService userService;

    private void checkAdmin(String auth) { ... }

    @GetMapping
    public ResponseEntity<List<XxxResponseDto>> getAll(@RequestHeader("Authorization") String auth) {
        checkAdmin(auth);
        return ResponseEntity.ok(xxxService.getAll());
    }
    // POST, PUT, DELETE similarly
}

Important

• Services never do manual mapping — always delegate to the mapper
• Every REST endpoint must have a checkAdmin() or checkAdminOrEntityManager() guard
• Use @ExceptionHandler(AuthException.class) at the bottom