Hibernate 学习代码/笔记(四)(一对多)

package com.hibernate.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

/**
* 单向一对多
* 一个班级对应多个学生
* @author cyx
*
*/
public class Grade implements Serializable {

private int gid;
private String gname;
private String gdesc;

//在一方定义一个多方的集合
private Set<Student> student = new HashSet<Student>();

public Set<Student> getStudent() {
return student;
}
public void setStudent(Set<Student> student) {
this.student = student;
}
public int getGid() {
return gid;
}
public void setGid(int gid) {
this.gid = gid;
}
public String getGname() {
return gname;
}
public void setGname(String gname) {
this.gname = gname;
}
public String getGdesc() {
return gdesc;
}
public void setGdesc(String gdesc) {
this.gdesc = gdesc;
}
public Grade(String gname, String gdesc) {
//		super();
this.gname = gname;
this.gdesc = gdesc;
}
public Grade() {
//		super();
}
}

package com.hibernate.entity;

/**
*
* @author cyx
*
*/
public class Student {

private int sid;
private String sname;
private String sex;

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;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "Student [sid=" + sid + ", sname=" + sname + ", sex=" + sex
+ "]";
}
public Student(String sname, String sex) {
//		super();
this.sname = sname;
this.sex = sex;
}
public Student() {
//		super();
}
}

<?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">

<!-- 班级对象关系映射 -->
<hibernate-mapping>
<class name="com.hibernate.entity.Grade" table="grade" >
<id name="gid" type="integer" column="gid">
<generator class="increment"/>
</id>
<property name="gname" type="string" column="gname" not-null="true" length="20"></property>
<property name="gdesc" column="gdesc"></property>

<!-- 配置单向一对多关联关系 -->
<set name="student" table="student">
<key column="gid"></key>	<!-- 指定关联的外键 -->
<one-to-many class="com.hibernate.entity.Student"/>
</set>

<!--
set元素常用属性:
name:	映射类属性的名称 也就是Garade实体类中,添加的student set集合
table:	关联类的目标数据库
lazy:	指定关联对象是否使用延时加载	默认为 proxy
inverse:表示双向关联中被动的一方		默认为 false
-->

</class>
</hibernate-mapping>

<?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">

<!-- 学生的对象关系映射 -->
<hibernate-mapping>
<class name="com.hibernate.entity.Student"  table="student">
<id name="sid" type="int" column="sid">
<generator class="increment"/>
</id>
<property name="sname" type="java.lang.String" column="sname" length="20" not-null="true"></property>
<property name="sex" type="java.lang.String" column="sex"></property>

</class>

</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.username">root</property>		<!-- 数据库用户名 -->
<property name="connection.password">1234</property>		<!-- 数据库密码 -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property><!-- 数据库驱动 -->
<!-- 数据库地址 -->
<property name="connection.url">jdbc:mysql://localhost:3306/test?user=root&password=1234&useUnicode=true&characterEncoding=UTF-8</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property><!-- mysql 数据库方言 -->

<property name="show_sql">true</property>
<property name="format_sql">false</property>
<property name="hbm2ddl.auto">update</property>

<mapping resource="com/hibernate/entity/Grade.hbm.xml"/>
<mapping resource="com/hibernate/entity/Student.hbm.xml"/>

</session-factory>
</hibernate-configuration>

package com.hibernate.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateUtil {

private static SessionFactory sessionFactory;
private static Session session;

static {
//创建配置对象
Configuration config = new Configuration().configure();
//创建服务注册对象
ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
//创建会话工厂对象
sessionFactory = config.buildSessionFactory(serviceRegistry);
//创建会话对象
//		session = sessionFactory.openSession();
}

//获取sessionFactory
public static SessionFactory getSessionFactory(){
return sessionFactory;
}

//获取session
public static Session getSession(){
session = sessionFactory.openSession();
return session;
}

//关闭session
public static void closeSession(Session session){
if(session != null){
session.close();
}
}
}

package com.hibernater.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.hibernate.entity.Grade;
import com.hibernate.entity.Student;
import com.hibernate.util.HibernateUtil;

public class TestOneToMany {

private Session session;
private HibernateUtil hibernateUtil;
private Transaction transaction;

/**
* 添加学生
*/
@Test
public void add(){
try{
session = hibernateUtil.getSession();
transaction = session.beginTransaction();

Grade grade = new Grade("JAVA一班", "软件开发");
Student student = new Student("小明", "男");
Student student2 = new Student("大明", "女");

//如果希望在学生表中添加对应的班级编号,需要在班级中添加学生,建立关系链接
grade.getStudent().add(student);
grade.getStudent().add(student2);

session.save(grade);
session.save(student);
session.save(student2);

transaction.commit();
}catch(Exception e){
transaction.rollback();
e.printStackTrace();
}finally{
if(session != null){
hibernateUtil.closeSession(session);
}
}
}

/**
* 查询班级中包含的学生
*/
@Test
public void findStudentByGrade(){
session = hibernateUtil.getSession();
Grade grade = (Grade)session.get(Grade.class, 1);
System.out.println(grade.getGname()+","+grade.getGdesc());

Set<Student> student = grade.getStudent();
for (Student student2 : student) {
System.out.println(student2.getSname()+","+student2.getSex());
}
}

/**
* 修改学生所属班级
*/
@Test
public void update(){
try{
session = hibernateUtil.getSession();
transaction = session.beginTransaction();

Grade grade = new Grade("PHP一班","软件开发");
Student studet = (Student)session.get(Student.class, 1);
grade.getStudent().add(studet);
session.save(grade);
transaction.commit();
}catch(Exception e){
transaction.rollback();
e.printStackTrace();
}finally{
if(session != null){
hibernateUtil.closeSession(session);
}
}
}

/**
* 删除学生
*/
@Test
public void delete(){
try{
session = hibernateUtil.getSession();
Transaction transaction = session.beginTransaction();

Student student = (Student)session.get(Student.class, 1);
session.delete(student);
transaction.commit();

}catch(Exception e){
e.printStackTrace();
transaction.rollback();
}finally{
if(session != null){
hibernateUtil.closeSession(session);
}
}
}
}