Spring BootJpa实体，映射与id和实体相同的引用列

Question

@Entity
@Table(name = "user")
public class User {
    @Id
    private UUID id;

    @Column(name = "name")
    private String name;

    ...

    // getter setter ignored for brevity
}

@Entity
@Table(name = "student")
public class Student {
    @Id
    private UUID id;

    @Column(name = "user_id")
    private UUID userId;

    @OneToOne
    @JoinColumn(name = "user_id", referencedColumnName = "id", 
                insertable = false, updatable = false)
    private UserEntity userEntity;

    ...

    // getter setter ignored for brevity
}

@Repository
public interface StudentRepository extend PagingAndSortingRepository<StudentEntity, UUID> {

  Optional<StudentEntity> findByUserId(UUID userId);
}

StudentEntity student = studentRepository.findByUserId(userId).get()
student.getUserId() --- this is present
student.getUserEntity() -- NULL

不确定为什么UserEntity没有被填充为此调用的一部分。

Answer 1

问题很可能是持久化上下文仍然包含以前保存的实体（没有用户集）。您首先必须清除持久性上下文并再次加载它才能看到一个非空用户。

无论如何，就像评论中建议的那样，我会建议您只映射用户。您不需要userid字段。按照您现在映射的方式,您应该可以使用以下内容：

Optional<StudentEntity> findByUserEntityId(UUID userId);

关于这个问题的更多信息，请阅读官方文档:https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.query-methods.query-property-expressions