ManyToMany 本身带有带有 EmbeddedId 的 AssociationTable

Question

在多对多关联期间，我在使用 Hibernate 时遇到了一些麻烦：/我想让一个用户拥有他的联系人。关联表用于包含关联的创建日期及其状态（例如活动、非活动等...）

• 休眠版本：5.2.17

• 弹簧靴：2.0.5

我的班级用户：

@Entity(name = "user")

public class User implements Serializable {

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)

@JoinTable(name = "assoc_user_user", joinColumns = {@JoinColumn(name = 

"id.myself.id")}, inverseJoinColumns = {@JoinColumn(name = 

"id.contact.id")})

private List<AssocUserUser> contacts;

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)

@JoinTable(name = "assoc_user_user", joinColumns = {@JoinColumn(name = 

"id.contact.id")}, inverseJoinColumns = {@JoinColumn(name = 

"id.myself.id")})

private List<AssocUserUser> contactOf;

}

我的协会类 AssocUserUser ：

@Entity(name = "assoc_user_user")

public class AssocUserUser implements Serializable {

private static final long serialVersionUID = 1L;

@EmbeddedId

private AssocUserUserId id;

@Column(name = "creation_date", nullable = false)

private LocalDateTime creationDate;

@Column(name = "status")

@Enumerated(EnumType.STRING)

private ContactStatusEnum status;

}

我的 EmbeddedId 类 AssocUserUserId ：

@Embeddable

public class AssocUserUserId implements Serializable {

private static final long serialVersionUID = 1L;

@ManyToOne

@JoinColumn(name = "user_id_myself", nullable = false)

private User myself;

@ManyToOne

@JoinColumn(name = "user_id_contact", nullable = false)

private User contact;

}

我的错误：

引起：org.hibernate.AnnotationException: A Foreign keyrefering com.....AssocUserUser from com.....User 有错误的列数。应该是 2

Answer 1

好吧，这个问题已经在Spring-Data-JPA ManyToMany 与额外列的关系中提出并回答，但我想它与自我引用有点不同。我不是所有JoinTable和JoinColumn注释的忠实粉丝，只是因为它们通常是多余的，恕我直言，用于更改默认值。我的答案不包括这些注释，因此请根据需要添加它们。请注意，对于 Spring-Data-Jpa，您需要每个实体的存储库，因此您需要关联实体的存储库。这与 JPA 中的单个实体管理器不同。这会稍微影响您处理关联实体的方式。在这里，我们通过创建和持久化新AssocUserUser实体来持久化新关系。我完成课程的方式是：@Entitypublic class User {&nbsp; &nbsp; @Id @GeneratedValue(strategy = GenerationType.IDENTITY)&nbsp; &nbsp; private Long id;&nbsp; &nbsp; @OneToMany(mappedBy="myself")&nbsp; &nbsp; private Set<AssocUserUser> contacts;@Entitypublic class AssocUserUser {&nbsp; &nbsp; @EmbeddedId&nbsp; &nbsp; private AssocUserUserId id = new AssocUserUserId();&nbsp; &nbsp; @ManyToOne @MapsId("myselfId")&nbsp; &nbsp; private User myself;&nbsp; &nbsp; @ManyToOne @MapsId("contactId")&nbsp; &nbsp; private User contact;@SuppressWarnings("serial")@Embeddablepublic class AssocUserUserId implements Serializable {&nbsp; &nbsp; private Long myselfId;&nbsp; &nbsp; private Long contactId;并Repositories为两个实体public interface UserRepository extends JpaRepository<User, Long> {&nbsp; &nbsp; @Query("select u from User u left outer join fetch u.contacts where u.id = :userId")&nbsp; &nbsp; User getContactsForUser(@Param("userId") Long userId);public interface AssocUserUserRepository extends JpaRepository<AssocUserUser, AssocUserUserId> {如何创建协会private void update() {&nbsp; &nbsp; User user1 = new User();&nbsp; &nbsp; User contact1 = new User();&nbsp; &nbsp; userRepo.save(user1);&nbsp; &nbsp; userRepo.save(contact1);&nbsp; &nbsp; AssocUserUser assoc = new AssocUserUser();&nbsp; &nbsp; assoc.setMyself(user1);&nbsp; &nbsp; assoc.setContact(contact1);&nbsp; &nbsp; assocUserUserRepo.save(assoc);}&nbsp; &nbsp;如何以Unidirectional时尚的方式阅读关联private void read() {&nbsp; &nbsp; User me = new User();&nbsp; &nbsp; me.setId(1L);&nbsp; &nbsp; AssocUserUser assoc = new AssocUserUser();&nbsp; &nbsp; assoc.setMyself(me);&nbsp; &nbsp; List<AssocUserUser> contacts = assocUserUserRepo.findAll(Example.of(assoc));&nbsp; &nbsp; System.out.println(contacts.size());}并以一种Bidirectional方式阅读关联：private void readBi() {&nbsp; &nbsp; User me = userRepo.getContactsForUser(1L);&nbsp; &nbsp; System.out.println(me.getContacts().size());}和往常一样，检查日志：create table assoc_user_user (contact_id bigint not null, myself_id bigint not null, primary key (contact_id, myself_id))create table user (id bigint generated by default as identity, primary key (id))alter table assoc_user_user add constraint FKaccetv956cu63fwiejjfrm0mi foreign key (contact_id) references useralter table assoc_user_user add constraint FK1absxfuktrjnom8vwtjfqx5l0 foreign key (myself_id) references userinsert into user (id) values (null)insert into user (id) values (null)select assocuseru0_.contact_id as contact_1_0_0_, assocuseru0_.myself_id as myself_i2_0_0_ from assoc_user_user assocuseru0_ where assocuseru0_.contact_id=? and assocuseru0_.myself_id=?select user0_.id as id1_1_0_ from user user0_ where user0_.id=?select user0_.id as id1_1_0_ from user user0_ where user0_.id=?insert into assoc_user_user (contact_id, myself_id) values (?, ?)select assocuseru0_.contact_id as contact_1_0_, assocuseru0_.myself_id as myself_i2_0_ from assoc_user_user assocuseru0_ inner join user user1_ on assocuseru0_.myself_id=user1_.id where user1_.id=1select user0_.id as id1_1_0_ from user user0_ where user0_.id=?select user0_.id as id1_1_0_ from user user0_ where user0_.id=?select user0_.id as id1_1_0_, contacts1_.contact_id as contact_1_0_1_, contacts1_.myself_id as myself_i2_0_1_, contacts1_.myself_id as myself_i2_0_0__, contacts1_.contact_id as contact_1_0_0__ from user user0_ left outer join assoc_user_user contacts1_ on user0_.id=contacts1_.myself_id where user0_.id=?select user0_.id as id1_1_0_ from user user0_ where user0_.id=?