多对多映射

多对多映射表现为在两个表之外产生一个中间表,其主键为两个表的外键.

如下:

Person与Event为多对多关联.除了产生person,event表外,还会产生person_event表.

映射文件:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.lwf.hibernate.many2many">
	<class name="Event" table="EVENTS">
		<id name="id" column="Event_ID">
			<generator class="native"/>
		</id>
		<property name="title"/>
		<property name="date" type="timestamp" column="Event_Date"/>
		<set name="participants" table="Person_Event" inverse="true">
			<key column="Event_ID"/>
			<many-to-many column="Person_id" class="Person"></many-to-many>
		</set>
	</class>
	
	<class name="Person" >
		<id name="id" column="Person_ID">
			<generator class="native"/>
		</id>
		<property name="name"/>
		<property name="age"/>
		<set name="events" table="Person_Event" >
			<key column="Person_id"/>
			<many-to-many column="Event_ID" class="Event"/>
		</set>
		<set name="emailAddress" table="Person_Email_Addr" >
			<key column="Person_id"/>
			<element type="string" column="Emai_Addr"/>
		</set>
		
	
	</class>
</hibernate-mapping>

 

 

POJO

package com.lwf.hibernate.many2many;

import java.util.HashSet;
import java.util.Set;

public class Person {

	private long id;
	private String name;
	private int age;
	private Set events = new HashSet();
	private Set emailAddress = new HashSet();
	
	public long getId() {
		return id;
	}
	public void setId(long 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 Set getEvents() {
		return events;
	}
	public void setEvents(Set events) {
		this.events = events;
	}
	public Set getEmailAddress(){
		return emailAddress;
	}
	public void setEmailAddress(Set emailAddress){
		this.emailAddress = emailAddress;
	}
}

 

package com.lwf.hibernate.many2many;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

public class Event {

	private long id;
	private String title;
	private Date date;
	private Set participants = new HashSet();
	
	public Event(){}

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public Date getDate() {
		return date;
	}

	public void setDate(Date date) {
		this.date = date;
	}

	public Set getParticipants() {
		return participants;
	}

	public void setParticipants(Set participants) {
		this.participants = participants;
	}
}

 

 

测试类:

package com.lwf.hibernate.many2many;

import java.util.Date;
import java.util.Iterator;
import java.util.Set;

import org.hibernate.Session;

import com.lwf.hibernate.util.HibernateUtil;
import com.lwf.hibernate.util.MapUtil;

public class Many2ManyTest {

	public static void main(String[] args) {
//		addPerson();
//		addEvent();
//		addPersonToEvent(1L,1L);
		//addEmaiAddrToPerson(1L,"[e-mail]");
//		save();
		load();
	}
	
	public static void load(){
		MapUtil map = new MapUtil();
		map.begin();
		Session session = map.getSession();
		Person aPerson = (Person)session.load(Person.class, 1L);
		System.out.println(aPerson.getName());
		Set events = aPerson.getEvents();
		for (Iterator iterator = events.iterator(); iterator.hasNext();) {
			Event event = (Event) iterator.next();
			System.out.println(event.getTitle());
			System.out.println(event.getDate());
			
		}
		
		
		map.commit();
		map.close();
	}

	public static void addEmaiAddrToPerson(Long personId,String emailAddr){
		Session session = HibernateUtil.getSession();
		session.beginTransaction();
		Person aPerson = (Person)session.load(Person.class, personId);
		aPerson.getEmailAddress().add(emailAddr);
		
		HibernateUtil.commit(session);
		
	}
	public static void addPersonToEvent(Long personId, Long eventId){
		Session session = HibernateUtil.getSession();
		session.beginTransaction();
		Person aPerson = (Person)session.load(Person.class, personId);
		Event anEvent = (Event)session.load(Event.class, eventId);
		aPerson.getEvents().add(anEvent);
		
		HibernateUtil.commit(session);
	}
	
	public static void addPerson(){
		Session session = HibernateUtil.getSession();
		session.beginTransaction();
		Person person = new Person();
		person.setName("li");
		person.setAge(16);
		session.save(person);
	
		HibernateUtil.commit(session);
	}
	
	public static void addEvent(){
		Session session = HibernateUtil.getSession();
		session.beginTransaction();
		Event event = new Event();
		event.setTitle("event_title2");
		event.setDate(new Date());
		session.save(event);
	
		HibernateUtil.commit(session);
	}
	
	public static void save(){
		MapUtil map = new MapUtil();
		map.begin();
		Person person = new Person();
		person.setName("person1");
		person.setAge(22);
		
		Event event = new Event();
		event.setTitle("title1");
		event.setDate(new Date());
		map.save(event);
		
		Event event1 = new Event();
		event1.setTitle("title2");
		event1.setDate(new Date());
		map.save(event1);
	
		person.getEvents().add(event);
		person.getEvents().add(event1);
		
		map.save(person);
		
		map.commit();
		map.close();
	}
}