Spring Data JPA

title: Spring Data JPA description: Spring Data JPA ka complete guide

ORM (Object Relational Mapping) — Java objects aur DB tables ko map karna.

JPA Annotations

java exampleWoHoTech

@Entity
@Table(name = "employees")
public class Employee {

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

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

    @Column(unique = true)
    private String email;

    @Enumerated(EnumType.STRING)
    private Department department;

    @CreationTimestamp
    private LocalDateTime createdAt;

    @UpdateTimestamp
    private LocalDateTime updatedAt;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "manager_id")
    private Employee manager;

    @OneToMany(mappedBy = "manager", cascade = CascadeType.ALL)
    private List<Employee> subordinates;
}

Repository Query Methods

java exampleWoHoTech

public interface EmployeeRepository extends JpaRepository<Employee, Long> {
    // Method name se query generate hoti hai
    List<Employee> findByDepartment(Department dept);
    List<Employee> findByNameContainingIgnoreCase(String keyword);
    Optional<Employee> findByEmail(String email);
    List<Employee> findBySalaryBetween(double min, double max);
    List<Employee> findByDepartmentOrderBySalaryDesc(Department dept);
    long countByDepartment(Department dept);
    boolean existsByEmail(String email);
    void deleteByDepartment(Department dept);

    // Custom JPQL
    @Query("SELECT e FROM Employee e WHERE e.salary > :minSalary AND e.department = :dept")
    List<Employee> findHighEarners(@Param("minSalary") double salary, @Param("dept") Department dept);

    // Native SQL
    @Query(value = "SELECT * FROM employees WHERE YEAR(created_at) = :year", nativeQuery = true)
    List<Employee> findByYear(@Param("year") int year);

    // Pagination
    Page<Employee> findByDepartment(Department dept, Pageable pageable);
}

Service with Pagination

java exampleWoHoTech

@Service
public class EmployeeService {
    @Autowired EmployeeRepository repo;

    public Page<Employee> getEmployees(int page, int size, String sortBy) {
        Pageable pageable = PageRequest.of(page, size, Sort.by(sortBy));
        return repo.findAll(pageable);
    }
}
// Controller: GET /api/employees?page=0&size=10&sortBy=name

title: Spring Data JPA description: Spring Data JPA ka complete guide

ORM (Object Relational Mapping) — Java objects aur DB tables ko map karna.

JPA Annotations

java exampleWoHoTech

@Entity
@Table(name = "employees")
public class Employee {

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

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

    @Column(unique = true)
    private String email;

    @Enumerated(EnumType.STRING)
    private Department department;

    @CreationTimestamp
    private LocalDateTime createdAt;

    @UpdateTimestamp
    private LocalDateTime updatedAt;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "manager_id")
    private Employee manager;

    @OneToMany(mappedBy = "manager", cascade = CascadeType.ALL)
    private List<Employee> subordinates;
}

Repository Query Methods

java exampleWoHoTech

public interface EmployeeRepository extends JpaRepository<Employee, Long> {
    // Method name se query generate hoti hai
    List<Employee> findByDepartment(Department dept);
    List<Employee> findByNameContainingIgnoreCase(String keyword);
    Optional<Employee> findByEmail(String email);
    List<Employee> findBySalaryBetween(double min, double max);
    List<Employee> findByDepartmentOrderBySalaryDesc(Department dept);
    long countByDepartment(Department dept);
    boolean existsByEmail(String email);
    void deleteByDepartment(Department dept);

    // Custom JPQL
    @Query("SELECT e FROM Employee e WHERE e.salary > :minSalary AND e.department = :dept")
    List<Employee> findHighEarners(@Param("minSalary") double salary, @Param("dept") Department dept);

    // Native SQL
    @Query(value = "SELECT * FROM employees WHERE YEAR(created_at) = :year", nativeQuery = true)
    List<Employee> findByYear(@Param("year") int year);

    // Pagination
    Page<Employee> findByDepartment(Department dept, Pageable pageable);
}

Service with Pagination

java exampleWoHoTech

@Service
public class EmployeeService {
    @Autowired EmployeeRepository repo;

    public Page<Employee> getEmployees(int page, int size, String sortBy) {
        Pageable pageable = PageRequest.of(page, size, Sort.by(sortBy));
        return repo.findAll(pageable);
    }
}
// Controller: GET /api/employees?page=0&size=10&sortBy=name

Spring Data JPA

JPA Annotations

Repository Query Methods

Service with Pagination

Continue learning this concept

Spring Data JPA

JPA Annotations

Repository Query Methods

Service with Pagination

Continue learning this concept