Spring Data:当子关系从父关系中删除时，如何自动删除子关系

Question

我有一个User实体，它持有一个@OneToOne关系中的Character实体。然而，我希望Character记录在与User实体分离后立即被删除。

这是我的User.kt实体类:

// User.kt
@Entity
class User(
@Id
var id: String,
var email: String,
@OneToOne(cascade = [CascadeType.ALL], orphanRemoval = true)
var character: Character?,
var isAdmin: Boolean
) { // ... }

下面是我用来测试这种行为的单元测试:

// UserRepositoryTest.kt
@Test
fun `should remove orphan character entity when being removed from user entity`() {
val user = UserTestTemplate.testUser()
val character = CharacterTestTemplate.testCharacter()
user.character = character
userRepository.save(user)
user.character = null
userRepository.save(user)
val actual = userRepository.findById(user.id).orElse(null)
assertThat(actual).isNotNull()
assertThat(actual.character).isNull()
val savedCharacter = characterRepository.findById(character.id)
assertThat(savedCharacter.get()).isNull() // fails
}

我添加了CascadeType.ALL和orphanRemoval = true选项，因为这些是我唯一读到的与我的请求相关的东西。

我在单元测试中所做的是创建一个用户和字符实例。然后向用户添加字符实例并通过UserRepository保存用户。感谢CascadeType.ALL字符实例将被自动保存。现在我想有同样的事情，当从用户删除字符。然而，这并不像您在单元测试 的最后一行中看到的那样工作。

Answer 1

有两点需要注意:

• 事务写模式
• 一级缓存

@Test
fun `should remove orphan character entity  entity`() {
val user = UserTestTemplate.testUser()
val character = CharacterTestTemplate.testCharacter()
user.character = character
userRepository.save(user)
user.character = null
//use saveAndFlush here to force immediate DB update
//otherwise may be deferred until transactional method returns
userRepository.saveAndFlush(user)
//clear the persistence context to ensure you will be reading from 
//the database rather than first level cache
//entityManager is injected to test via @PersistenceContext annotation
entityManager.clear();
//now you are guaranteed a db read reflecting all flushed updates
val actual = userRepository.findById(user.id).orElse(null)
assertThat(actual).isNotNull()
assertThat(actual.character).isNull()
val savedCharacter = characterRepository.findById(character.id)
assertThat(savedCharacter.get()).isNull() // fails
}