休眠OneToOne关系 [英] Hibernate OneToOne relationship

问题描述

我有两个持久化实体： User 和 UserDetail 。他们有一对一的关系。我使用hibernate注释。但我正在为我的数据库获取一个用户信息的几个对象。显然，我对Hibernate注释的了解并不是很好解决这个问题。

用户 class：

  @Entity 
 @Table（name =USER）
 public class User {
 
 @Id 
 @GeneratedValue 
 @Column（name =ID）
私人长ID; 
 
 @Column（name =NAME）
私人字符串名称; 
 
 @Column（name =PASSWORD）
私人字符串密码; 
 
 @OneToOne（mappedBy =user，cascade = CascadeType.ALL）
 private UserDetail userDetail; 
 
 // setters and getters 
 
} 
  

UserDetail 类：

  @Entity 
 @Table（name =USER_DETAIL） 
 public class UserDetail {
 
 @OneToOne 
 @JoinColumn（name =USER_ID）
 private用户用户; 
 
 //其他字段
 
} 
  

我在我的代码中使用这个如下：

  UserDetail userDetail = new UserDetail（）; 
 userDetail.setInfo（info）; 
 userDetail.setUser（seventhUser）; 
 hibernateTemplate.saveOrUpdate（userDetail）; 
  

一切正常。以下是我的表 USER_DETAIL ：

但是当我尝试更改用户信息时，出现错误行为。在我再次设置用户信息后，我得到了下面的表格：

  UserDetail newUserDetail = new UserDetail（）; 
 newUserDetail.setInfo（newInfo）; 
 newUserDetail.setUser（seventhUser）; 
 hibernateTemplate.saveOrUpdate（newUserDetail）; 
  

为什么相同的两个信息对象对应一个用户？我有一对一的关系。我怎样才能避免这种情况？我做错了什么？

解决方案

如果您想修改现有的 UserDetail ，那么你必须设置它的ID，或者从会话中获取并修改它。否则，Hibernate认为这是一个新的必须保存的，因为它没有任何ID。

  UserDetail existingUserDetail = session .get（UserDetail.class，theUserDetailId）; 
 existingUserDetail.setInfo（newInfo）; 
  

为了确保不会为同一用户保存两个UserDetail实例，您应该添加一个独特的约束在 UserDetail 数据库表的 USER_ID 列上。

I have two persistence entity: User and UserDetail. They have one-to-one relationship. I use hibernate annotations. But I am getting in my database several objects of user information for one same user. Apparently my knowledge of Hibernate annotations are not so good to solve this problem.

User class:

@Entity
@Table(name = "USER")
public class User {

   @Id
   @GeneratedValue
   @Column(name = "ID")
   private Long id; 

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

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

   @OneToOne(mappedBy = "user", cascade = CascadeType.ALL)
   private UserDetail userDetail;

   // setters and getters

}

UserDetail class:

@Entity
@Table(name = "USER_DETAIL")
public class UserDetail {  

   @OneToOne
   @JoinColumn(name = "USER_ID")
   private User user;

   // other fields

}

I use this in my code as follows:

UserDetail userDetail = new UserDetail();
userDetail.setInfo(info);
userDetail.setUser(seventhUser);
hibernateTemplate.saveOrUpdate(userDetail);

And everything works properly. Here's what my table USER_DETAIL:

But when I try to change user information, I get an incorrect behavior. I get following table after I again set user information:

UserDetail newUserDetail = new UserDetail();
newUserDetail.setInfo(newInfo);
newUserDetail.setUser(seventhUser);
hibernateTemplate.saveOrUpdate(newUserDetail);

Why the same two objects of information correspond to one user?? I have One-To-One relationship. How can I avoid this? What am I doing wrong?

解决方案

If you want to modify an existing UserDetail, then you must set its ID, or get it from the session and modify it. Else, Hibernate thinks it's a new one that must be saved, since it doesn't have any ID.

UserDetail existingUserDetail = session.get(UserDetail.class, theUserDetailId);
existingUserDetail.setInfo(newInfo);

To make sure you don't save two UserDetail instances for the same user, you should add a unique constraint on the USER_ID column of the UserDetail database table.

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