게시글을 지우는 기능을 추가할 때, 외래키로 연관이 되어있는 댓글을 삭제할지 결정해야 한다.
이때 설정해주어야 하는 설정은 Cascade라 불리는 전파속성이다.
CascadeType.ALL
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상위 엔터티에서 하위 엔터티로 모든 작업을 전파
@Entity
public class Person {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
@OneToMany(mappedBy = "person", cascade = CascadeType.ALL)
private List<Address> addresses;
}
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@Entity
public class Address {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String street;
private int houseNumber;
private String city;
private int zipCode;
@ManyToOne(fetch = FetchType.LAZY)
private Person person;
}
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CascadeType.PERSIST
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하위 엔티티까지 영속성 전달
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Person Entity를 저장하면 Address Entity도 저장
@Test
public void whenParentSavedThenChildSaved() {
Person person = new Person();
Address address = new Address();
address.setPerson(person);
person.setAddresses(Arrays.asList(address));
session.persist(person); // persist 동작 수행
session.flush();
session.clear();
}
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Hibernate: insert into Person (name, id) values (?, ?)
Hibernate: insert into Address (
city, houseNumber, person_id, street, zipCode, id) values (?, ?, ?, ?, ?, ?)
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CascadeType.MERGE
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하위 엔티티까지 병합 작업을 지속
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Address와 Person 엔티티를 조회한 후 업데이트
@Test
public void whenParentSavedThenMerged() {
int addressId;
Person person = buildPerson("devender");
Address address = buildAddress(person);
person.setAddresses(Arrays.asList(address));
session.persist(person);
session.flush();
addressId = address.getId();
session.clear();
Address savedAddressEntity = session.find(Address.class, addressId);
Person savedPersonEntity = savedAddressEntity.getPerson();
savedPersonEntity.setName("devender kumar");
savedAddressEntity.setHouseNumber(24);
session.merge(savedPersonEntity); // merge 동작 수행
session.flush();
}
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Hibernate: select address0_.id as id1_0_0_, address0_.city as city2_0_0_, address0_.houseNumber as houseNum3_0_0_, address0_.person_id as person_i6_0_0_, address0_.street as street4_0_0_, address0_.zipCode as zipCode5_0_0_ from Address address0_ where address0_.id=?
Hibernate: select person0_.id as id1_1_0_, person0_.name as name2_1_0_ from Person person0_ where person0_.id=?
Hibernate: update Address set city=?, houseNumber=?, person_id=?, street=?, zipCode=? where id=?
Hibernate: update Person set name=? where id=?
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CascadeType.REMOVE
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하위 엔티티까지 제거 작업을 지속
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연결된 하위 엔티티까지 엔티티 제거
@Test
public void whenParentRemovedThenChildRemoved() {
int personId;
Person person = buildPerson("devender");
Address address = buildAddress(person);
person.setAddresses(Arrays.asList(address));
session.persist(person);
session.flush();
personId = person.getId();
session.clear();
Person savedPersonEntity = session.find(Person.class, personId);
session.remove(savedPersonEntity); // remove 동작 수행
session.flush();
}
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Hibernate: delete from Address where id=?
Hibernate: delete from Person where id=?
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CascadeType.REFRESH
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데이터베이스로부터 인스턴스 값을 다시 읽어 오기(새로고침)
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연결된 하위 엔티티까지 인스턴스 값 새로고침
@Test
public void whenParentRefreshedThenChildRefreshed() {
Person person = buildPerson("devender");
Address address = buildAddress(person);
person.setAddresses(Arrays.asList(address));
session.persist(person);
session.flush();
person.setName("Devender Kumar");
address.setHouseNumber(24);
session.refresh(person); // refresh 동작 수행
assertThat(person.getName()).isEqualTo("devender");
assertThat(address.getHouseNumber()).isEqualTo(23);
}
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CascadeType.DETACH
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영속성 컨텍스트에서 엔티티 제거
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연결된 하위 엔티티까지 영속성 제거
@Test
public void whenParentDetachedThenChildDetached() {
Person person = buildPerson("devender");
Address address = buildAddress(person);
person.setAddresses(Arrays.asList(address));
session.persist(person);
session.flush();
assertThat(session.contains(person)).isTrue();
assertThat(session.contains(address)).isTrue();
session.detach(person); // detach 동작 수행 시 영속성 컨텍스트에 존재하지 않음.
assertThat(session.contains(person)).isFalse();
assertThat(session.contains(address)).isFalse();
}
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