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One-to-Many Delete

Hibernate

Dalam materi kita akan membahas penghapusan data dalam relasi tabel One-to-Many. Pembahasan materi delete ini akan dibahas dari sisi parrent(Classes) dan delete dari sisi child(Student).

1️⃣ Entity Parrent: Classes.java​

@Entity
@Table(name = "classes")
public class Classes {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer id;
	
	@Column(name = "class_name")
	private String className;
	
	@OneToOne(cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
	@JoinColumn(name = "teacher_id")
	private Teacher teacher;
	
	@OneToMany(
		mappedBy = "classes",
		fetch = FetchType.LAZY,
		cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
	List<Student> students = new ArrayList<>();

	// Setter & Getter

}

2️⃣ Entity Child: Student.java​

Sisi @ManyToOne secara default bersifat EAGER, pada kasus ini kita tidak perlu mengubahnya kecuali kita ingin menjadikannya LAZY.

@Entity
@Table(name = "student")
public class Student {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer id;
	
	@Column(name = "first_name")
	private String firstName;
	
	@Column(name = "last_name")
	private String lastName;
	
	@ManyToOne(cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
	@JoinColumn(name = "class_id")
	private Classes classes;
	
	// Setter & Getter

}

3️⃣ Delete Parrent Classes​

Pada contoh kasus ini kita akan menghapus data Classes tanpa menghapus data dalam Student yang terkait. Step-by-step delete data Classes:

  • Mencari Classes ID.
  • Memutuskan hubungan dengan Student yang terkait dengan Classes tersebut.
  • Menghapus Classes.

🛢️ Update Repository / DAO​

  • Pada Implementasi DAO kita akan merubah deleteClassesById:
@Repository
public class SchoolDAOImpl implements SchoolDAO {

	private EntityManager entityManager;
	
	public SchoolDAOImpl(EntityManager entityManager) {
		this.entityManager = entityManager;
	}

	@Override
	@Transactional
	public void deleteClassesById(Integer id) {
		Classes classes = entityManager.find(Classes.class, id);
		List<Student> students = classes.getStudents();
		
		// menghapus semua referensi Classes dalam data Student sebelum dihapus
		for (Student student : students) {
			student.setClasses(null);
		}
		
		// hapus referensi objek terkait dan putuskan tautan bi-directiona
		classes.getTeacher().setClasses(null);
				
		entityManager.remove(classes);	
	}

	// Implementasi method Lainnya

}

▶️ Main Class​

  • Studi kasus kita memiliki data dalam database sbb:

mysql> select * from teacher;
+----+------------+-----------+
| id | first_name | last_name |
+----+------------+-----------+
|  1 | Inti       | Astuti    |
|  2 | Hatake     | Kakashi   |
|  3 | John       | Chena     |
+----+------------+-----------+

mysql> select * from classes;
+----+------------+------------+
| id | class_name | teacher_id |
+----+------------+------------+
|  2 | Kelas 12   |          1 |
|  3 | Kelas 11   |          2 |
|  5 | Kelas 10   |          3 |
+----+------------+------------+

mysql> select * from student;
+----+------------+-----------+----------+
| id | first_name | last_name | class_id |
+----+------------+-----------+----------+
|  1 | John       | Key       |        5 |
|  2 | Abu        | Nawas     |        5 |
|  4 | Indra      | Birowo    |        2 |
|  5 | Ibnu       | Jamil     |        2 |
|  6 | Tora       | Sudiro    |        2 |
|  7 | Uzumaki    | Naruto    |        3 |
|  8 | Uciha      | Sazuke    |        3 |
|  9 | Rock       | Lee       |        3 |
+----+------------+-----------+----------+

Kita akan menghapus data Classes dengan id 5, dan data pada Student terkait tidak ikut terhapus.

  • Pada main class application kita akan menghapus data Classes yang memiliki id 5:
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

	// Bean ini akan dieksekusi di command line
	@Bean
	public CommandLineRunner commandLineRunner(SchoolDAO dao) {
		return runner -> {
			
			deleteClasses(dao);
			
		};
	}

	private void deleteClasses(SchoolDAO dao) {
		Integer id = 5;
		dao.deleteClassesById(id);
		System.out.println("Classes deleted with id " + id);
	}
}
  • Output pada Hibernate SQL:
Hibernate: select c1_0.id,c1_0.class_name,t1_0.id,t1_0.first_name,t1_0.last_name from classes c1_0 left join teacher t1_0 on t1_0.id=c1_0.teacher_id where c1_0.id=?
Hibernate: select s1_0.class_id,s1_0.id,s1_0.first_name,s1_0.last_name from student s1_0 where s1_0.class_id=?
Hibernate: update student set class_id=?,first_name=?,last_name=? where id=?
Hibernate: update student set class_id=?,first_name=?,last_name=? where id=?
Hibernate: delete from classes where id=?
Classes deleted with id 5
  • Cek perubahan dalam database, data Clases dengan id 5 seharusnya sudah terhapus.
mysql> select * from classes;
+----+------------+------------+
| id | class_name | teacher_id |
+----+------------+------------+
|  2 | Kelas 12   |          1 |
|  3 | Kelas 11   |          2 |
+----+------------+------------+

mysql> select * from student;
+----+------------+-----------+----------+
| id | first_name | last_name | class_id |
+----+------------+-----------+----------+
|  1 | John       | Key       |     NULL |
|  2 | Abu        | Nawas     |     NULL |
|  4 | Indra      | Birowo    |        2 |
|  5 | Ibnu       | Jamil     |        2 |
|  6 | Tora       | Sudiro    |        2 |
|  7 | Uzumaki    | Naruto    |        3 |
|  8 | Uciha      | Sazuke    |        3 |
|  9 | Rock       | Lee       |        3 |
+----+------------+-----------+----------+

4️⃣ Delete Child Student​

Pada contoh kasus ini kita akan menghapus data Student, tanpa menghapus data Classes terkait.

🛢️ Repository / DAO​

  • Menambahkan method baru pada interface DAO dengan menambahkan method deleteStudentById untuk menghandle menghapus data Student:
public interface SchoolDAO {

	void saveClasses(Classes classes);
	
	Classes findClassById(Integer id);
	
	void deleteClassesById(Integer id);
	
	Teacher findTeacherById(Integer id);
	
	void deleteTeacherById(Integer id);
	
	List<Student> findStudentByClassId(Integer id);
	
	Classes findClassesByIdJoinFetch(Integer id);
	
	void updateClasses(Classes classes);
	
	Student findStudentById(Integer id);
	
	void updateStudent(Student student);
	
	void deleteStudentById(Integer id);
	
}
  • Implementasi DAO:
@Repository
public class SchoolDAOImpl implements SchoolDAO {

	private EntityManager entityManager;
	
	public SchoolDAOImpl(EntityManager entityManager) {
		this.entityManager = entityManager;
	}

	@Override
	@Transactional
	public void deleteStudentById(Integer id) {
		entityManager.remove(entityManager.find(Student.class, id));	
	}

	// Implementasi method Lainnya

}

▶️ Main Class​

  • Pada main class application kita akan menghapus data Student yang memiliki id 5:
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

	// Bean ini akan dieksekusi di command line
	@Bean
	public CommandLineRunner commandLineRunner(SchoolDAO dao) {
		return runner -> {
			
			deleteStudent(dao);
			
		};
	}

	private void deleteStudent(SchoolDAO dao) {
		int id = 5;
		dao.deleteStudentById(id);		
	}
}
  • Output pada Hibernate SQL:
Hibernate: select s1_0.id,c1_0.id,c1_0.class_name,t1_0.id,t1_0.first_name,t1_0.last_name,s1_0.first_name,s1_0.last_name from student s1_0 left join classes c1_0 on c1_0.id=s1_0.class_id left join teacher t1_0 on t1_0.id=c1_0.teacher_id where s1_0.id=?
Hibernate: delete from student where id=?
info

Source Code: https://github.com/TimposuLabs/belajar-springboot-jpa-hibernate-advance/tree/main/09-hibernate-one-to-many-delete