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Hibernate!!多对多(单向|双向)关联映射

时间:2014-12-18 16:23:20      阅读:284      评论:0      收藏:0      [点我收藏+]

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多对多——单向关联映射

 1 package com.hb.model;
 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.ManyToMany;
10 import javax.persistence.Table;
11 
12 @Entity
13 @Table(name="t_teacher")
14 public class Teacher {
15     private  int  tid ;
16     private  String  tname;
17     private  Set<Student>  students = new  HashSet<Student>();
18     
19     @Id
20     @GeneratedValue
21     public int getTid() {
22         return tid;
23     }
24     public void setTid(int tid) {
25         this.tid = tid;
26     }
27     public String getTname() {
28         return tname;
29     }
30     public void setTname(String tname) {
31         this.tname = tname;
32     }
33     @ManyToMany
34     public Set<Student> getStudents() {
35         return students;
36     }
37     public void setStudents(Set<Student> students) {
38         this.students = students;
39     }
40     
41     
42 
43 }
package com.hb.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_student")
public class Student {
    private  int sid; 
    private  String   sname;
    
    @Id
    @GeneratedValue
    public int getSid() {
        return sid;
    }
    public void setSid(int sid) {
        this.sid = sid;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    
    

}

生成的表如下:

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这样生成的中间表的名称是自动生成的,也可以通过加入一些属性改变表的名称

只需要在Teacher类里面添加一些属性,修改后的代码如下:

 1 @Entity
 2 @Table(name="t_teacher")
 3 public class Teacher {
 4     private  int  tid ;
 5     private  String  tname;
 6     private  Set<Student>  students = new  HashSet<Student>();
 7     
 8     @Id
 9     @GeneratedValue
10     public int getTid() {
11         return tid;
12     }
13     public void setTid(int tid) {
14         this.tid = tid;
15     }
16     public String getTname() {
17         return tname;
18     }
19     public void setTname(String tname) {
20         this.tname = tname;
21     }
22     @ManyToMany
23     @JoinTable(name="t_s",  //表名
24             joinColumns={ @JoinColumn(name="teacher_id")},  //  ???
25             inverseJoinColumns={@JoinColumn(name="student_id")}  // 对方那张表的对应的外键的id 
26         )
27     public Set<Student> getStudents() {
28         return students;
29     }
30     public void setStudents(Set<Student> students) {
31         this.students = students;
32     }
33 }

 

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多对多单向关联在xml文件中的配置

 1 <hibernate-mapping>
 2     <class name="com.hb.model.Teacher">
 3         <id name="tid">
 4             <generator class="native"></generator>
 5         </id>
 6         
 7         <property name="tname"></property>
 8         <set name="students" table="t_s">
 9             <key column="teacher_id"></key>
10             <many-to-many class="com.hb.model.Student" column="student_id"/>
11         </set>
12     </class>
13     
14 </hibernate-mapping>

多对多——双向关联映射

  • 很少用到
  • 双向总会用到mappedBy

 

Hibernate!!多对多(单向|双向)关联映射

标签:des   style   blog   ar   io   color   os   sp   for   

原文地址:http://www.cnblogs.com/Mokaffe/p/4158536.html

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