hibernate - ManyToMany关联删除连接表条目

Question

我使用这两个实体来创建一个新用户和它关联的组:

@Entity  
@Table(name="usertable")  
@SuppressWarnings("serial")  
@Searchable  
public class User implements Serializable {  

    @GeneratedValue(generator="userIdSeq")  
    @SequenceGenerator(name="userIdSeq", sequenceName="usertable_id_seq")      
    @SearchableId  
    @Id  
    int id;  

    @SearchableProperty  
    String userId;                      // 'Unique identifier. It is formed using this fashion: ''prefix:identifier''  
    String userName;                    // Name used to log in the application.  
    String email;                       // User's email  

    @ManyToMany  
    @JoinTable( name="usergroup",  
                joinColumns=@JoinColumn(name = "userid", referencedColumnName="userId"),  
                inverseJoinColumns=@JoinColumn(name = "groupid")  
    )  
    List<Group> groups;  

    ...  
}  

// Group  
@Entity  
@Table(name="grouptable")  
public class Group implements Serializable {  
    @Id  
    String groupId                  // Unique identifier for group.  
    String description              // Brief text describing the group purposes.  

    @ManyToMany(mappedBy="groups")  
    @Cascade(SAVE_UPDATE)  
    List<User> users  

    ....  
}  

在数据库上:
用户表(id、userId、名称)
分组表(ID，描述)
用户组(用户 ID、组 ID、组 key )

将 Group 添加到组列表中，在 User 上调用 save 方法并观看 hibernate 将 usergoup 保存在一起是非常令人满意的。但是，当我在保存(用户)操作后检索用户时，我有一个大问题，即 hibernate 自动从用户组表中删除条目。

下面是生成删除用户组的测试序列

保存新用户

保存新组

并将组列在用户

中

保存用户

从电子邮件中获取用户

    @Test    @Transactional    public void testGetUserByEmail(){        Session session = factory.getCurrentSession();         String email = "sarah.silverman@comedycentral.com";         User user = createUser();         user.setWeCanContact(true);         user.setPartnersCanContact(false);         user.setAgreedTerms(false);         user.setReferer("Laura");        String groupId = "AARP";         String description = "Appletalk Address Resolution Protocol";         Group group1 = new Group();         group1.setGroupId(groupId);         group1.setDescription(description);         session.save(group1);         session.flush();         user.getGroupLists().add(group1);         session.saveOrUpdate(user);         User testUser = userRepository.getUserByEmail(email);        assertNotNull(testUser);         assertEquals("It's not the correct email", email, testUser.getEmail());     }

    private User createUser(){
        Session session = factory.getCurrentSession(); 
        String userId = "UB:2010"; 
        String userPassword = "sarah"; 
        String realName = "Sarah Silverman"; 
        String email = "sarah.silverman@comedycentral.com"; 

        User user = new User();
        user.setUserId(userId); 
        user.setUserName(email); 
        user.setUserPassword(userPassword); 
        user.setRealName(realName); 
        user.setEmail(email); 

        List<Group> emptyGroupLists = new ArrayList<Group>(); 
        user.setGroupLists(emptyGroupLists); 
        Group group = new Group(); 
        group.setGroupId("ABC"); 
        group.setDescription("A for apple");
        user.getGroupLists().add(group);
        session.save(group); 
        session.save(user); 

        session.flush();
        return user; 
    }

// Repository Method to get user from email// //  @NamedQuery(name="user.findByEmail",//       query="SELECT u FROM User u " +//    "LEFT JOIN FETCH u.groupLists " +//              "WHERE upper(u.email) = :email")public User getUserByEmail(String email) {    Session session = sessionFactory.getCurrentSession();     Query query = session.getNamedQuery("user.findByEmail");    query.setParameter("email", email.toUpperCase());    User user = (User)query.uniqueResult();    return user; }

Before executing step 5, usergroup with automatically removed like // SQL output

Hibernate:
delete
from
usergroup
where
userid=? 

我要注意的几件事；
1. userid 不是用户对象的 pk。那会是问题吗？
2. userid 和 groupid 映射的 usergroup 中的 manyTomany 映射
3. 它不仅发生在测试中。它也在开发中。

如何停止用户组的自动删除。用户组是非常重要的表，不应删除。任何帮助将非常感激。谢谢你。

Answer 1

让我们看看用户

public class User {

    @Id
    @GeneratedValue
    private Integer id;

    @ManyToMany
    @JoinTable(name="USER_GROUP",  
        joinColumns=@JoinColumn(name="USER_ID", referencedColumnName="USER_ID"),
        inverseJoinColumns=@JoinColumn(name="GROUP_ID")
    )
    private List<Group> groupList = new ArrayList<Group>();

}

现在我们的集团

public class Group {

    @Id
    private String id;

    @ManyToMany(mappedBy="groupList")
    @Cascade(SAVE_UPDATE)
    private List<User> userList = new ArrayList<User>();

}

在继续之前，让我们简单地看一下 userList 字段

// Group.java

@ManyToMany(mappedBy="groupList")
@Cascade(SAVE_UPDATE)
private List<User> userList = new ArrayList<User>();

@Cascade(SAVE_UPDATE) 表示

Save Or Update each referenced User

mappingBy="groupList"的意思是

For each REFERENCED user, see whether it has a reference to me (Group object). If so, set up our bidirectional relationship. So if you want to link User and Group through USER_GROUP table, each REFERENCED user has to have a reference to a Group object.

现在让我们看看 testGetUserByEmail 方法中发生了什么

Group group = new Group(); 
group.setId(groupId);

// group.getUserList(); returns a empty List, right ?
// As there is no User with reference to group in group.getUserList();
// So NO LINK between Group and User through USER_GROUP table
session.save(group);

// It explains why your link is missing
// You need to set up both sides
user.getGroupLists().add(group);

// Just save a User
// Nothing else
session.saveOrUpdate(user);

在 createUser 方法中，您有与上图相同的场景

所以我的建议是

When using bidirectional relationship, ALWAYS use a add convenience method

// Group.java
public void addUser(User user) {
    user.getGroupList().add(this);

    getUserList().add(user);
}

// User.java
public void addGroup(Group group) {
    group.getUserList().add(this);

    getGroupList().add(group);
}

问候，