Hibernate关联映射 --- 多对多实例分析（双向关联）
一 概念分析
1．多对多的经典实例（Teacher – Student）
二 代码分析
1．Teacher类
package com.hbsi.domain;
import java.util.Set;
//单向一对多 Teacher 一 对 多 Student
public class Teacher {
private int id;
private String name;
private Set<Student> students;
public Teacher() {
super();
// TODO Auto-generated constructor stub
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}
2．Stduent类
package com.hbsi.domain;
import java.util.Set;
public class Student {
private int id;
private String name;
private Set<Teacher> teachers;
public Student() {
super();
// TODO Auto-generated constructor stub
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}
}
3．Teacher的映射文件 Teacher.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.hbsi.domain">
<class name="Teacher" table="teacher">
<id name="id" column="id">
<generator class="native" />
</id>
<property name="name" column="name" />
<!-- 集合属性的体现 多对多 table属性指定的是中间表的名字 -->
<set name="students" table="teacher_student">
<!--查中间表的外键 和老师的id的关联 老师的id-->
<key column="teacher_id"/>
<!-- 查学生的id和中间表的关系 -->
<many-to-many class="Student" column="student_id"></many-to-many>
</set>
</class>
</hibernate-mapping>
4.Student的映射文件 Student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.hbsi.domain">
<class name="Student" table="student">
<id name="id" column="id">
<generator class="native" />
</id>
<property name="name" column="name" />
<set name="teachers" table="teacher_student">
<key column="student_id"></key><!-- 查找这个学生被那个老师教 -->
<many-to-many class="Teacher" column="teacher_id"></many-to-many>
</set>
</class>
</hibernate-mapping>