JPA 다대다 관계에서 Join Table Insert 하지 않는 이유가 궁금합니다.

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다대다 관계 테스트 코드를 작성했는데 테스트 메소드에 @Transaction이 선언되었을 때, 이상하게도 Join Table에만 Insert하는 Query가 실행되지 않습니다. 구체적인 코드는 다음과 같습니다. 엔티티 클래스와 repository 클래스입니다.부모(1) <-> 자식(N)자식(N) <-> 태그(M)@Entity @Table(name = "parent") public class ParentEntity { @Id @Column(name = "parent_id") @GeneratedValue(strategy = GenerationType.IDENTITY) private long id; @Column private String parentValue; @OneToMany(mappedBy = "parentEntity", cascade = CascadeType.PERSIST) private List childs = new ArrayList<>(); } @Entity @Table(name = "child") public class ChildEntity { @Id @Column(name = "child_id") @GeneratedValue(strategy = GenerationType.IDENTITY) private long id; @Column private String childValue; @ManyToOne @JoinColumn(name="parent_id") private ParentEntity parentEntity; @ManyToMany(cascade = CascadeType.PERSIST) @JoinTable( name = "child_tag", joinColumns = @JoinColumn(name = "child_id", nullable = false), inverseJoinColumns = @JoinColumn(name = "tag_id", nullable = false) ) private Set tags; } @Entity @Table(name = "Tag") public class TagEntity { @Column(name = "tag_id") @Id @GeneratedValue(strategy = GenerationType.IDENTITY) long tagId; @Column String value; @ManyToMany(mappedBy = "tags") private List childs; } @Repository @Transactional public class TestRepository { @Autowired private EntityManager em; public void saveParent(ParentEntity parent) { em.persist(parent); } } 아래는 테스트 코드입니다.@Test public void test() { ParentEntity parentEntity = new ParentEntity(); parentEntity.setParentValue("parent value"); ChildEntity childEntity1 = new ChildEntity(); childEntity1.setChildValue("child1 value"); ChildEntity childEntity2 = new ChildEntity(); childEntity2.setChildValue("child2 value"); TagEntity tagEntity = new TagEntity(); tagEntity.setValue("tag1 value"); TagEntity tagEntity2 = new TagEntity(); tagEntity.setValue("tag2 value"); TagEntity tagEntity3 = new TagEntity(); tagEntity.setValue("tag3 value"); Set tags1 = new HashSet<>(); tags1.add(tagEntity); tags1.add(tagEntity2); Set tags2 = new HashSet<>(); tags1.add(tagEntity2); tags1.add(tagEntity3); childEntity1.setTags(tags1); childEntity2.setTags(tags2); tagEntity.setChilds(Collections.singletonList(childEntity1)); tagEntity2.setChilds(Arrays.asList(childEntity1, childEntity2)); tagEntity3.setChilds(Collections.singletonList(childEntity2)); childEntity1.setParentEntity(parentEntity); childEntity2.setParentEntity(parentEntity); parentEntity.getChilds().add(childEntity1); parentEntity.getChilds().add(childEntity2); repository.saveParent(parentEntity); } }위 코드 그대로 실행시켰을 때 로그는 다음과 같습니다.Hibernate: insert into parent (parent_value) values (?) Hibernate: insert into child (child_value, parent_id) values (?, ?) Hibernate: insert into tag (value) values (?) Hibernate: insert into tag (value) values (?) Hibernate: insert into tag (value) values (?) Hibernate: insert into child (child_value, parent_id) values (?, ?) Hibernate: insert into child_tag (child_id, tag_id) values (?, ?) Hibernate: insert into child_tag (child_id, tag_id) values (?, ?) Hibernate: insert into child_tag (child_id, tag_id) values (?, ?)ㅏ 테스트 메소드에 @Transcational 어노테이션을 선언했을 때 로그는 다음과 같습니다.2019-06-10 23:14:03.359 INFO 6618 --- [ main] o.s.t.c.transaction.TransactionContext : Began transaction (1) for test context [DefaultTestContext@6379eb testClass = PracticeApplicationTests, testInstance = com.momentjin.practice.PracticeApplicationTests@13d289c7, testMethod = test@PracticeApplicationTests, testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@294425a7 testClass = PracticeApplicationTests, locations = '{}', classes = '{class com.momentjin.practice.PracticeApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@56aac163, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@396f6598, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@4232c52b, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2a556333], resourceBasePath = 'src/main/webapp', contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.web.ServletTestExecutionListener.activateListener' -> true, 'org.springframework.test.context.web.ServletTestExecutionListener.populatedRequestContextHolder' -> true, 'org.springframework.test.context.web.ServletTestExecutionListener.resetRequestContextHolder' -> true]]; transaction manager [org.springframework.orm.jpa.JpaTransactionManager@6d969330]; rollback [true] Hibernate: insert into parent (parent_value) values (?) Hibernate: insert into child (child_value, parent_id) values (?, ?) Hibernate: insert into tag (value) values (?) Hibernate: insert into tag (value) values (?) Hibernate: insert into tag (value) values (?) Hibernate: insert into child (child_value, parent_id) values (?, ?) 2019-06-10 23:14:03.514 INFO 6618 --- [ main] o.s.t.c.transaction.TransactionContext : Rolled back transaction for test: [DefaultTestContext@6379eb testClass = PracticeApplicationTests, testInstance = com.momentjin.practice.PracticeApplicationTests@13d289c7, testMethod = test@PracticeApplicationTests, testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@294425a7 testClass = PracticeApplicationTests, locations = '{}', classes = '{class com.momentjin.practice.PracticeApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@56aac163, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@396f6598, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@4232c52b, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@2a556333], resourceBasePath = 'src/main/webapp', contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.web.ServletTestExecutionListener.activateListener' -> true, 'org.springframework.test.context.web.ServletTestExecutionListener.populatedRequestContextHolder' -> true, 'org.springframework.test.context.web.ServletTestExecutionListener.resetRequestContextHolder' -> true]] 왜 이런 현상이 발생하는 건가요? 구글링해도 답을 찾지 못했습니다 ㅠ선배님들의 조언이 필요합니다. 감사합니다.

D3Master · Answer

음... 왜 그런지 디테일하게는 모르겠으나,,,transactional 어노테이션이 repository에도 걸려있는데 test에도 어노테이션이 걸리면 뭔가 꼬이는 현상으로 첫번째 추측을 해보구요..transactional로 영속성이 유지되는 상태에서 연결 테이블에 insert가 되지 않는건 연관 관계에 있는 테이블들이 flush 된 후 연결 테이블이 insert 될 수 있기 때문에 그런 현상이 일어나지 않나 추측해봅니다.. 제 생각으론 각각의 쿼리때 마다 영속성 컨텍스트에 어떤놈들이 물려있나, 각각 같은 트랜잭션에서 돌아가나 트레이싱 해보면 굉장히 유익한 공부가 되지 않을까 싶네요..저도 궁금해지니 나중에 알게 되시면 자문자답 부탁드립니다~

JPA 다대다 관계에서 Join Table Insert 하지 않는 이유가 궁금합니다.

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