hibernate:many-to-many
以学生和老师为例
建表语句:
CREATE DATABASE `manytomany`
CHARACTER SET 'utf8';
USE `manytomany`;
DROP TABLE IF EXISTS `student`;
create table student(
sid int auto_increment primary key,
name varchar(10) not null
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `teacher`;
create table teacher(
tid int auto_increment primary key,
name varchar(10) not null
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `st`;
create table st(
sid int not null,
tid int not null
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
Teacher.java
package com.test.domain;
import java.util.HashSet;
import java.util.Set;
public class Teacher implements java.io.Serializable {
private Integer tid;
private String name;
private Set students = new HashSet();
public Teacher() {
}
public Teacher(String name) {
this.name = name;
}
public Integer getTid() {
return this.tid;
}
public void setTid(Integer tid) {
this.tid = tid;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public Set getStudents() {
return students;
}
public void setStudents(Set students) {
this.students = students;
}
}
Student.java:
package com.test.domain;
import java.util.HashSet;
import java.util.Set;
public class Student implements java.io.Serializable {
private Integer sid;
private String name;
private Set teachers = new HashSet();
public Student() {
}
public Student(String name) {
this.name = name;
}
public Integer getSid() {
return this.sid;
}
public void setSid(Integer sid) {
this.sid = sid;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public Set getTeachers() {
return teachers;
}
public void setTeachers(Set teachers) {
this.teachers = teachers;
}
}
Teacher.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.test.domain.Teacher" table="teacher" catalog="manytomany">
<id name="tid" type="java.lang.Integer">
<column name="tid" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="name" length="10" not-null="true" />
</property>
<!--inverse="false": 由teacher操作student -->
<set name="students" table="st" cascade="save-update" inverse="false">
<key column="tid"></key>
<many-to-many class="com.test.domain.Student" column="sid">
</many-to-many>
</set>
</class>
</hibernate-mapping>
Student.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.test.domain.Student" table="student" catalog="manytomany">
<id name="sid" type="java.lang.Integer">
<column name="sid" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="name" length="10" not-null="true" />
</property>
<!--inverse="true": 由teacher操作student -->
<set name="teachers" table="st" cascade="save-update" inverse="true">
<key column="sid"></key>
<many-to-many class="com.test.domain.Teacher" column="tid">
</many-to-many>
</set>
</class>
</hibernate-mapping>
测试类,Test.java
package com.test.dao;
import org.hibernate.Session;
import com.test.domain.Student;
import com.test.domain.Teacher;
public class Test {
public static void main(String[] args) {
Session session = HibernateSessionFactory.getSession();
Teacher teacher1 = new Teacher();
teacher1.setName("teacher1");
Teacher teacher2 = new Teacher();
teacher2.setName("teacher2");
Teacher teacher3 = new Teacher();
teacher3.setName("teacher3");
Student student1 = new Student();
student1.setName("student1");
Student student2 = new Student();
student2.setName("student2");
//student1.getTeachers().add(teacher1);student1.getTeachers().add(teacher2);student2.getTeachers().add(teacher1);这几句代码可以不要,因为Teacher掌握主动权。所以下面几句代码给注释掉了
// //学生一有2个老师
// student1.getTeachers().add(teacher1);
// student1.getTeachers().add(teacher2);
//
// //学生二有一个老师
// student2.getTeachers().add(teacher1);
//因为老师是inverse="false" ,老师掌握主动权
//第一个老师有2个学生
teacher1.getStudents().add(student1);
teacher1.getStudents().add(student2);
//第二个老师有一个学生
teacher2.getStudents().add(student1);
session.saveOrUpdate(teacher1);
session.saveOrUpdate(teacher2);
session.beginTransaction().commit();
session.close();
/**执行的sql
Hibernate: insert into manytomany.teacher (name) values (?)
Hibernate: insert into manytomany.student (name) values (?)
Hibernate: insert into manytomany.student (name) values (?)
Hibernate: insert into manytomany.teacher (name) values (?)
Hibernate: insert into st (tid, sid) values (?, ?)
Hibernate: insert into st (tid, sid) values (?, ?)
Hibernate: insert into st (tid, sid) values (?, ?)
*/
}
}
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