关于一个级联“查询操作”，如果用事务提交的话会删除数据，不知道在哪里写错了。

-------------User.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 package="com.accp.demo">
	<class name="User" table="t_user">
		<id name="userId">
			<generator class="native" />
		</id>
		<property name="userName" />
		<many-to-one name="role" class="Role" column="roleId" />
	</class>
</hibernate-mapping>

-----------Role.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 package="com.accp.demo">
	<class name="Role" table="t_role">
		<id name="roleId">
			<generator class="native" />
		</id>
		<property name="roleName" />
		<set name="users" cascade="save-update" inverse="true">
			<key column="roleId"/>
			<one-to-many class="User"/>
		</set>
		<set name="rights" table="t_role_right" cascade="save-update">
			<key column="roleId" />
			<many-to-many class="Right" column="rightId" />
		</set>
	</class>
</hibernate-mapping>

-----------------Right.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 package="com.accp.demo">
	<class name="Right" table="t_right">
		<id name="rightId">
			<generator class="native" />
		</id>
		<property name="rightName" />
		<set name="roles" table="t_role_right" cascade="save-update">
			<key column="rightId"/>
			<many-to-many class="Role" column="roleId"/>
		</set>
	</class>
</hibernate-mapping>

-----------------Many2manyTest.java-----------------

package com.accp.demo;

import java.util.Iterator;

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

import com.accp.demo.utils.HibernateUtils;

public class Many2manyTest {
	@Test
	public void searchUserRights() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			User user = (User)session.get(User.class, 1);
			System.out.println(user.getRole().getRoleName());
			Iterator itr = user.getRole().getRights().iterator();
			while(itr.hasNext()){
				Right right = (Right)itr.next();
				System.out.println(right.getRightName());
			}
			session.beginTransaction().commit();
		} catch (HibernateException e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		} finally {
			HibernateUtils.closeSession(session);
		}
	}
}

====================执行结果如下=====================
Hibernate: select user0_.userId as userId0_0_, user0_.userName as userName0_0_, user0_.roleId as roleId0_0_ from t_user user0_ where user0_.userId=?
Hibernate: select role0_.roleId as roleId1_0_, role0_.roleName as roleName1_0_ from t_role role0_ where role0_.roleId=?
manager
Hibernate: select rights0_.roleId as roleId1_, rights0_.rightId as rightId1_, right1_.rightId as rightId3_0_, right1_.rightName as rightName3_0_ from t_role_right rights0_ left outer join t_right right1_ on rights0_.rightId=right1_.rightId where rights0_.roleId=?
search user
delete user
Hibernate: delete from t_role_right where rightId=?
Hibernate: delete from t_role_right where rightId=?

------------------------------------------
其中很奇怪多执行了如下操作
Hibernate: delete from t_role_right where rightId=?
Hibernate: delete from t_role_right where rightId=?

查询不用事务是没问题，但我执行了事务后怎么就删除数据了。
大家帮我分析一下why。谢谢。