多对一（一对多）的双向关联

一个组（Group）有多个用户（User），进行多对一（一对多）的双向配置，在数据库中生成的表结构如下图：

多对一（一对多）的双向关联

　　Annotation配置：

　　　　　　Group:

 1 package com.bjsxt.hibernate;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 import javax.persistence.Entity;
 7 import javax.persistence.GeneratedValue;
 8 import javax.persistence.Id;
 9 import javax.persistence.OneToMany;
10 import javax.persistence.Table;
11 
12 @Entity
13 @Table(name="t_group")
14 public class Group {
15     private Integer id;
16     
17     private String name;
18     
19     private Set<User> users = new HashSet<User>();
20 
21     @Id
22     @GeneratedValue
23     public Integer getId() {
24         return id;
25     }
26 
27     public void setId(Integer id) {
28         this.id = id;
29     }
30 
31     public String getName() {
32         return name;
33     }
34 
35     public void setName(String name) {
36         this.name = name;
37     }
38 
39     @OneToMany(mappedBy="group")//表示和User是一对多的关系，并且以User的group属性为准，自己就不做映射配置了
40     public Set<User> getUsers() {
41         return users;
42     }
43 
44     public void setUsers(Set<User> users) {
45         this.users = users;
46     }
47 }

　　　　　　User:

 1 package com.bjsxt.hibernate;
 2 
 3 import javax.persistence.Entity;
 4 import javax.persistence.GeneratedValue;
 5 import javax.persistence.Id;
 6 import javax.persistence.JoinColumn;
 7 import javax.persistence.ManyToOne;
 8 import javax.persistence.Table;
 9 
10 @Entity
11 @Table(name="t_user")
12 public class User {
13     private Integer id;
14     
15     private String name;
16     
17     private Group group;
18     
19     @Id
20     @GeneratedValue
21     public Integer getId() {
22         return id;
23     }
24 
25     public void setId(Integer id) {
26         this.id = id;
27     }
28 
29     public String getName() {
30         return name;
31     }
32 
33     public void setName(String name) {
34         this.name = name;
35     }
36 
37     @ManyToOne
38     @JoinColumn(name="group_ID")//指定列名为 group_ID
39     public Group getGroup() {
40         return group;
41     }
42 
43     public void setGroup(Group group) {
44         this.group = group;
45     }
46 }

　　　　XML 配置：

　　　　　　Group:

 1 package com.bjsxt.hibernate;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 public class Group {
 7     private Integer id;
 8     
 9     private String name;
10     
11     private Set<User> users = new HashSet<User>();
12 
13     public Integer getId() {
14         return id;
15     }
16 
17     public void setId(Integer id) {
18         this.id = id;
19     }
20 
21     public String getName() {
22         return name;
23     }
24 
25     public void setName(String name) {
26         this.name = name;
27     }
28 
29     public Set<User> getUsers() {
30         return users;
31     }
32 
33     public void setUsers(Set<User> users) {
34         this.users = users;
35     }
36 }

View Code