Hibernate同一性问题

package com.cg.foo;

// Generated 2012-7-19 11:40:57 by Hibernate Tools 3.4.0.CR1

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

/**
 * TUser generated by hbm2java
 */
public class TUser implements java.io.Serializable {

	private long id;
	private String name;
	private String nickname;
	private Date birthday;
	private Set<TCard> TCards = new HashSet<TCard>(0);

	public TUser() {
	}

	public TUser(long id) {
		this.id = id;
	}

	public TUser(long id, String name, String nickname, Date birthday,
			Set<TCard> TCards) {
		this.id = id;
		this.name = name;
		this.nickname = nickname;
		this.birthday = birthday;
		this.TCards = TCards;
	}

	public long getId() {
		return this.id;
	}

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

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getNickname() {
		return this.nickname;
	}

	public void setNickname(String nickname) {
		this.nickname = nickname;
	}

	public Date getBirthday() {
		return this.birthday;
	}

	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}

	public Set<TCard> getTCards() {
		return this.TCards;
	}

	public void setTCards(Set<TCard> TCards) {
		this.TCards = TCards;
	}
	
	@Override
	public boolean equals(Object other) {
		if(this==other)return true;
		//if(id==null)return false;
		if(!(other instanceof TUser))return false;
		final TUser that = (TUser)other;
		return this.id == that.id;
	}

	@Override
	public int hashCode() {
//		return id==null? System.identityHashCode(this):this.id.hashCode();
		return (int)id;
	}
}




package com.cg.test;

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

import org.hibernate.Session;
import org.hibernate.tutorial.util.HibernateUtil;
import org.junit.Test;

import com.cg.foo.TUser;

public class TestObjIdentityEqual {

	@Test
	public void test() {
		Session session = HibernateUtil.getSessionFactory().openSession();
		session.beginTransaction();
		TUser a =(TUser) session.get(TUser.class	, 7L);
		TUser b =(TUser) session.get(TUser.class	, 7L);
		System.out.println("测试1个session的get对象同一性：");
		System.out.println(a == b);	//true
		
		session.getTransaction().commit();
		session.close();
		
		Session session2 = HibernateUtil.getSessionFactory().openSession();
		session2.beginTransaction();
		TUser c = (TUser) session2.get(TUser.class, 7L);
		
		System.out.println("测试两个session的get对象同一性：");
		System.out.println(a == c);		//false: detached & persisted
		
		session2.getTransaction().commit();
		session2.close();
		
		Set<TUser>	setAll =new HashSet();
		setAll.add(a);
		setAll.add(b);
		setAll.add(c);
		System.out.println(setAll.size());	//size:2
		
	}

}