📚 Bài viết thuộc series Java Backend Zero to Hello 📌 Phần: Phase 5: Spring Framework & Spring Boot | Bài 50/86

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BÀI 5.4: SPRING DATA JPA

Mục tiêu

• Sử dụng Spring Data JPA
• Tạo Repository interface
• Method naming convention
• Custom query với @Query

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1. SPRING DATA JPA LÀ GÌ?

Spring Data JPA là module của Spring Data, giúp đơn giản hóa việc truy cập database với JPA.

Lợi ích

• Ít code boilerplate
• Tự động generate query
• Hỗ trợ pagination, sorting
• Tích hợp với Spring Boot

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2. DEPENDENCY

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

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <scope>runtime</scope>
</dependency>

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3. ENTITY

@Entity
@Table(name = "users")
@Data  // Lombok
@NoArgsConstructor
@AllArgsConstructor
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;

    private Integer age;

    @Column(name = "created_at", updatable = false)
    @CreationTimestamp
    private LocalDateTime createdAt;

    @UpdateTimestamp
    private LocalDateTime updatedAt;
}

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4. REPOSITORY

4.1 JpaRepository

public interface UserRepository extends JpaRepository<User, Long> {
    // Tự động có sẵn:
    // save(), findById(), findAll(), deleteById(), count(), ...
}

4.2 CrudRepository

public interface UserRepository extends CrudRepository<User, Long> {
    // CRUD cơ bản
}

4.3 PagingAndSortingRepository

public interface UserRepository extends PagingAndSortingRepository<User, Long> {
    // Hỗ trợ pagination, sorting
}

4.4 Các method có sẵn

Method	Mô tả
save(entity)	Lưu (insert/update)
findById(id)	Tìm theo ID
findAll()	Lấy tất cả
findAllById(ids)	Tìm theo nhiều ID
count()	Đếm
existsById(id)	Kiểm tra tồn tại
deleteById(id)	Xóa theo ID
delete(entity)	Xóa entity
deleteAll()	Xóa tất cả

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5. METHOD NAMING CONVENTION

Spring Data tự động generate query từ tên method.

5.1 Cú pháp

findBy + PropertyName + Condition + OrderBy + PropertyName + Direction

5.2 Ví dụ

public interface UserRepository extends JpaRepository<User, Long> {

    // Tìm theo field
    Optional<User> findByEmail(String email);

    List<User> findByName(String name);

    List<User> findByAge(Integer age);

    // Điều kiện
    List<User> findByAgeGreaterThan(Integer age);

    List<User> findByAgeLessThanEqual(Integer age);

    List<User> findByNameLike(String pattern);

    List<User> findByNameContaining(String keyword);

    List<User> findByNameStartingWith(String prefix);

    List<User> findByNameEndingWith(String suffix);

    List<User> findByAgeBetween(Integer min, Integer max);

    List<User> findByAgeIn(Collection<Integer> ages);

    List<User> findByNameIsNull();

    List<User> findByNameIsNotNull();

    // Boolean
    List<User> findByActiveTrue();

    List<User> findByActiveFalse();

    // Kết hợp AND/OR
    List<User> findByNameAndEmail(String name, String email);

    List<User> findByNameOrEmail(String name, String email);

    // Sắp xếp
    List<User> findByAgeOrderByNameAsc(Integer age);

    List<User> findByAgeOrderByNameDesc(Integer age);

    // Giới hạn
    List<User> findFirst10ByOrderByAgeDesc();

    User findFirstByOrderByCreatedAtDesc();

    // Đếm
    long countByAgeGreaterThan(Integer age);

    boolean existsByEmail(String email);

    // Xóa
    long deleteByAgeLessThan(Integer age);
}

5.3 Từ khóa hỗ trợ

Keyword	SQL
Is, Equals	=
Not	<>
Like	LIKE
Containing	LIKE %x%
StartingWith	LIKE x%
EndingWith	LIKE %x
GreaterThan	>
LessThan	<
Between	BETWEEN
In	IN
IsNull	IS NULL
IsNotNull	IS NOT NULL
True	= true
False	= false
And	AND
Or	OR
OrderBy	ORDER BY

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6. @QUERY - CUSTOM QUERY

6.1 JPQL

public interface UserRepository extends JpaRepository<User, Long> {

    @Query("SELECT u FROM User u WHERE u.email = :email")
    Optional<User> findByEmailCustom(@Param("email") String email);

    @Query("SELECT u FROM User u WHERE u.age >= :minAge ORDER BY u.name")
    List<User> findAdults(@Param("minAge") int minAge);

    @Query("SELECT u.name, u.email FROM User u")
    List<Object[]> findNameAndEmail();

    @Query("SELECT new com.example.dto.UserDTO(u.name, u.email) FROM User u")
    List<UserDTO> findAllDTO();
}

6.2 Native Query

@Query(value = "SELECT * FROM users WHERE email = :email", nativeQuery = true)
Optional<User> findByEmailNative(@Param("email") String email);

6.3 Update Query

@Modifying
@Query("UPDATE User u SET u.name = :name WHERE u.id = :id")
int updateName(@Param("id") Long id, @Param("name") String name);

6.4 Delete Query

@Modifying
@Query("DELETE FROM User u WHERE u.age < :age")
int deleteOldUsers(@Param("age") int age);

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7. PAGINATION

public interface UserRepository extends JpaRepository<User, Long> {

    Page<User> findByAgeGreaterThan(int age, Pageable pageable);

    Slice<User> findByNameContaining(String name, Pageable pageable);
}

Sử dụng

Pageable pageable = PageRequest.of(0, 10, Sort.by("name").ascending());
Page<User> page = userRepository.findByAgeGreaterThan(18, pageable);

List<User> content = page.getContent();
int totalPages = page.getTotalPages();
long totalElements = page.getTotalElements();
boolean hasNext = page.hasNext();

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8. SORTING

List<User> findAll(Sort.by("name").ascending());
List<User> findAll(Sort.by(Sort.Order.asc("lastName"), Sort.Order.desc("firstName")));

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9. CUSTOM REPOSITORY

9.1 Interface

public interface UserRepositoryCustom {
    List<User> findByCustomQuery();
}

9.2 Implementation

@Repository
@RequiredArgsConstructor
public class UserRepositoryImpl implements UserRepositoryCustom {

    @PersistenceContext
    private EntityManager em;

    @Override
    public List<User> findByCustomQuery() {
        return em.createQuery("SELECT u FROM User u WHERE ...", User.class)
                 .getResultList();
    }
}

9.3 Kết hợp

public interface UserRepository extends JpaRepository<User, Long>, UserRepositoryCustom {
}

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10. SPECIFICATIONS (Dynamic Query)

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

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

    public static Specification<User> hasMinAge(Integer age) {
        return (root, query, cb) ->
            age == null ? null : cb.greaterThanOrEqualTo(root.get("age"), age);
    }
}

// Sử dụng
Specification<User> spec = Specification.where(hasName("An"))
    .and(hasMinAge(18));
List<User> users = userRepository.findAll(spec);

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11. ENTITY GRAPH (Eager Loading)

@Entity
@NamedEntityGraph(name = "User.orders",
    attributeNodes = @NamedAttributeNode("orders"))
public class User {
    @OneToMany(mappedBy = "user")
    private List<Order> orders;
}

@EntityGraph(value = "User.orders")
Optional<User> findById(Long id);

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12. AUDITING

@EntityListeners(AuditingEntityListener.class)
@MappedSuperclass
public abstract class Auditable {
    @CreatedDate
    private LocalDateTime createdAt;

    @LastModifiedDate
    private LocalDateTime updatedAt;

    @CreatedBy
    private String createdBy;

    @LastModifiedBy
    private String updatedBy;
}

Enable: @EnableJpaAuditing trên main class.

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13. BÀI TẬP THỰC HÀNH

Bài 1: User Repository

Tạo UserRepository với:

• findByEmail
• findByAgeGreaterThan
• existsByUsername
• countByStatus

Bài 2: Custom Query

Viết query:

• Tìm user có nhiều orders nhất
• Tính tổng giá trị orders

Bài 3: Pagination

Implement API trả về user có phân trang.

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14. TÓM TẮT

Khái niệm	Mô tả
JpaRepository	Interface chính
Method Naming	Tự sinh query
@Query	Custom JPQL/Native
Pageable	Phân trang
Sort	Sắp xếp
Specification	Dynamic query
EntityGraph	Eager loading
Auditing	Tự động track

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Bài tiếp theo: 5.5 Spring Web MVC

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🧭 Điều Hướng Series

⬅️ Bài trước: BÀI 5.3: BEAN & DEPENDENCY INJECTION

📋 Lộ trình tổng quan: Xem Toàn Bộ Series

➡️ Bài tiếp theo: BÀI 5.5: SPRING WEB MVC