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在JPA或Hibernate中更新许多关系

jpa hibernate java

Mr. Mak · 技术社区 · 6 年前

我有两个 Entity 就像下面。。。

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

    private String name;

    @ManyToMany(fetch = FetchType.LAZY, mappedBy = "groupMemberList")
    @Fetch(FetchMode.SELECT)
    private List<Group> groupList = new ArrayList<>();

    // Getters - Setters
}


@Entity
@Table(name = "GROUP")
public class Group {
    @Id
    private Long id;

    private String name;

    @ManyToMany(fetch = FetchType.LAZY/*, mappedBy = "groupList"*/)
    @Fetch(FetchMode.SELECT)
    @JoinTable(name = "SEC_GROUP_VS_MEMBER", joinColumns = @JoinColumn(name = "GROUP_ID"),
            inverseJoinColumns = @JoinColumn(name = "MEMBER_ID"))
    private List<User> groupMemberList;

    // Getters - Setters
}

我想更新 User Group 有时用下面的方法。。。

方法#1

public boolean updateGroup(Long groupId, List<Staff> groupMemberList) {
    Group group = hibernateTemplate.get(Group.class, groupId);

    group.setGroupMemberList(groupMemberList);
    hibernateTemplate.merge(group); // Group updated with the users
    return true;
}

public boolean updateUser(Long userId, List<Group> groupList) {
    User user = hibernateTemplate.get(User.class, userId);

    user.setGroupList(groupList);
    hibernateTemplate.merge(user); // User not updated with the groups
    return true;
}

第一种方法很好,但第二种方法不行。但当我移动 join table 从 Group.class User.class 第二种方法很好,而不是第一种。

1 回复 | 直到 6 年前

K.Nicholas 6 年前

这个问题是个问题 Owning Entity 问题。

Staff 是的一个子类 User ,您的问题是关系中只有一方是所属实体。这个 mappedBy = "groupMemberList" 使 Group 实体拥有的实体,因此只保留对该实体的更改。这意味着您必须更新 groupMemberList 组 两种情况下的实体。如果您有一个 用户 然后您必须遍历组列表并添加去吧。这个 groupList 用户 仅用于检索。

鉴于 GroupMember

@Entity
public class User {
    @Id @GeneratedValue
    private Long id;

    @ManyToMany(mappedBy = "groupMemberList")
    private List<GroupMember> groupList;

@Entity
public class GroupMember {
    @Id @GeneratedValue
    private Long id;

    @ManyToMany
    private List<User> groupMemberList;

然后:

// create starting user and membergroup    
tx.begin();
User user = new User();
em.persist(user);
GroupMember group = new GroupMember();
em.persist(group);
tx.commit();
em.clear();

// update users for groupId 2
System.out.println("update users for groupId 2");
tx.begin();
List<User> users = new ArrayList<>();
users.add(user);
group.setGroupMemberList(users);
em.merge(group);            
tx.commit();
em.clear();

// update groups for userId 1 -- doesn't work, not owner of relationship
System.out.println("update groups for userId 1 -- doesn't work, not owner of relationship");
tx.begin();
List<GroupMember> groups = new ArrayList<>();
groups.add(group);
user.setGroupList(groups);
em.merge(user);            
tx.commit();
em.clear();

// update groups for userId 1 -- works
System.out.println("update groups for userId 1 -- works");
tx.begin();
for ( GroupMember groupMember: groups) {
    groupMember.getGroupMemberList().add(user);
    em.merge(groupMember);            
}
tx.commit();
em.clear();

提供以下SQL输出:

Hibernate: insert into User (id) values (?)
Hibernate: insert into GroupMember (id) values (?)
update users for groupId 2
Hibernate: select groupmembe0_.id as id1_0_0_ from GroupMember groupmembe0_ where groupmembe0_.id=?
Hibernate: select groupmembe0_.groupList_id as groupLis1_1_0_, groupmembe0_.groupMemberList_id as groupMem2_1_0_, user1_.id as id1_4_1_ from GroupMember_User groupmembe0_ inner join User user1_ on groupmembe0_.groupMemberList_id=user1_.id where groupmembe0_.groupList_id=?
Hibernate: select user0_.id as id1_4_0_ from User user0_ where user0_.id=?
Hibernate: insert into GroupMember_User (groupList_id, groupMemberList_id) values (?, ?)
update groups for userId 1 -- doesn't work, not owner of relationship
Hibernate: select user0_.id as id1_4_0_ from User user0_ where user0_.id=?
Hibernate: select groupmembe0_.id as id1_0_0_ from GroupMember groupmembe0_ where groupmembe0_.id=?
update groups for userId 1 -- works
Hibernate: select groupmembe0_.id as id1_0_0_ from GroupMember groupmembe0_ where groupmembe0_.id=?
Hibernate: select groupmembe0_.groupList_id as groupLis1_1_0_, groupmembe0_.groupMemberList_id as groupMem2_1_0_, user1_.id as id1_4_1_ from GroupMember_User groupmembe0_ inner join User user1_ on groupmembe0_.groupMemberList_id=user1_.id where groupmembe0_.groupList_id=?
Hibernate: delete from GroupMember_User where groupList_id=?
Hibernate: insert into GroupMember_User (groupList_id, groupMemberList_id) values (?, ?)
Hibernate: insert into GroupMember_User (groupList_id, groupMemberList_id) values (?, ?)

参考文献: MappedBy in bi-directional @ManyToMany : what is the reason

JPA - difference in the use of the mappedBy property to define the owning entity