hibernate 的映射关系

一对多与多对一的映射关系的数据库表如下：

可以这样的来实现：

package cn.hnpi.lis.entity.ch615t;

import java.util.Set;

public class Classes {

private Integer id;

private String name;

private Set<Student> students;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public void setStudents(Set<Student> students) {

this.students = students;

}

public Set<Student> getStudents() {

return students;

}

}

package cn.hnpi.lis.entity.ch615t;

public class Student {

private Integer id;

private String name;

private int age;

private Classes classes;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public Classes getClasses() {

return classes;

}

public void setClasses(Classes classes) {

this.classes = classes;

}

}

Classes.hbm.xml的实现文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<!-- xml中书写提示：Alt+/ -->

<hibernate-mapping package="cn.hnpi.lis.entity.ch615t">

<class name="Classes" table="t_classes">

<id name="id">

<generator class="native" />

</id>

<property name="name"></property>

<!-- inverse="true":一的一段不维护映射关系，交给多的一方去维护 -->

<set name="students" inverse="true">

<key column="classes_id"></key>

<one-to-many class="Student"/>

</set>

</class>

</hibernate-mapping>

Student.hbm.xml的文件：

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<!-- xml中书写提示：Alt+/ -->

<hibernate-mapping package="cn.hnpi.lis.entity.ch615t">

<class name="Student" table="t_student">

<id name="id">

<generator class="native" />

</id>

<property name="age"></property>

<property name="name"></property>

<many-to-one name="classes" class="Classes" column="classes_id"></many-to-one>

</class>

</hibernate-mapping>

Hibernate的映射文件：

<mapping resource="cn/hnpi/lis/entity/ch615t/Student.hbm.xml" />

<mapping resource="cn/hnpi/lis/entity/ch615t/Classes.hbm.xml" />

测试代码：

package cn.hnpi.lis.entity.ch615t;

import java.util.HashSet;

import java.util.Set;

import org.hibernate.Session;

import org.hibernate.Transaction;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import cn.hnpi.lis.utils.HibernateUtil;

public class MyTest {

Session session;

Transaction tx ;

@Before

public void init(){

session = HibernateUtil.getSession();

tx = session.beginTransaction();

}

@After

public void close(){

tx.commit();

HibernateUtil.closeSession(session);

}

@Test

public void testSave(){

Student[]stus=new Student[10];

Classes[] classes = new Classes[3];

for(int i=0;i<stus.length;i++){

stus[i] = new Student();

stus[i].setAge(20+i);

stus[i].setName("zhangsan"+i);

}

for(int i=0;i<classes.length;i++){

classes[i] = new Classes();

classes[i].setName("class"+i);

}

stus[0].setClasses(classes[0]);

stus[1].setClasses(classes[0]);

stus[2].setClasses(classes[0]);

stus[3].setClasses(classes[1]);

stus[4].setClasses(classes[1]);

stus[5].setClasses(classes[1]);

stus[6].setClasses(classes[2]);

stus[7].setClasses(classes[2]);

stus[8].setClasses(classes[2]);

stus[9].setClasses(classes[2]);

for(int i=0;i<stus.length;i++){

session.save(stus[i]);

}

for(int i=0;i<classes.length;i++){

session.persist(classes[i]);

}

}

@Test

public void testLoad(){

}

}

测试结果如下：