多对一的单向关联

多对一与一对多
1.多对一单向关联
a) 项目名称：
b) 数据库表设计：在多方加外键
c) annotation:@Many2One
d) xml:<many-to-one>

 

多对一：从多配置到一

案例：一个组（Group）有多个用户（User），配置从User到Group的多对一的单向关联

　　Annotation:

　　　　Group类:

 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.Table;
 7 
 8 @Entity
 9 @Table(name="t_group")
10 public class Group {
11     private Integer id;
12     
13     private String name;
14 
15     @Id
16     @GeneratedValue
17     public Integer getId() {
18         return id;
19     }
20 
21     public void setId(Integer id) {
22         this.id = id;
23     }
24 
25     public String getName() {
26         return name;
27     }
28 
29     public void setName(String name) {
30         this.name = name;
31     }
32 }

　　　　User 类：

 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="groupId")//设置列的名称，可以不写，默认为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 public class Group {
 4     private Integer id;
 5     
 6     private String name;
 7 
 8     public Integer getId() {
 9         return id;
10     }
11 
12     public void setId(Integer id) {
13         this.id = id;
14     }
15 
16     public String getName() {
17         return name;
18     }
19 
20     public void setName(String name) {
21         this.name = name;
22     }
23 }
View Code

　　　　Group.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4         "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 5 
 6 <hibernate-mapping package="com.bjsxt.hibernate">
 7     <class name="Group" table="t_group">
 8         <id name="id" column="id">
 9             <generator class="native"/>
10         </id>
11         <property name="name" column="name" />
12     </class>
13 </hibernate-mapping>

　　　　User:

 1 package com.bjsxt.hibernate;
 2 
 3 public class User {
 4     private Integer id;
 5     
 6     private String name;
 7     
 8     private Group group;
 9 
10     public Integer getId() {
11         return id;
12     }
13 
14     public void setId(Integer id) {
15         this.id = id;
16     }
17 
18     public String getName() {
19         return name;
20     }
21 
22     public void setName(String name) {
23         this.name = name;
24     }
25 
26     public Group getGroup() {
27         return group;
28     }
29 
30     public void setGroup(Group group) {
31         this.group = group;
32     }
33 }
View Code

　　　　User.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3         "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4         "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 5 
 6 <hibernate-mapping package="com.bjsxt.hibernate">
 7     <class name="User" table="t_user">
 8         <id name="id" column="id">
 9             <generator class="native"/>
10         </id>
11         <property name="name" column="name" />
12         <many-to-one name="group" column="groupId" />
13     </class>
14 </hibernate-mapping>

上面两种配置的效果一样：

jar包链接: https://pan.baidu.com/s/1qY356PY 密码: bm8f

代码链接: https://pan.baidu.com/s/1o7F4HIE 密码: ap4m

posted @ 2017-04-19 19:49  流年如水烟雨随风  阅读(410)  评论(0)  编辑  收藏  举报