Hibernate的rollback不起作用？解决方法

<hibernate-mapping package="com.example.hibernate">
    <class name="IdCard" table="t_idcard">
        <id name="id">
            <generator class="native" />
        </id>
        <property name="cardNo" unique="true"/>
    </class>
</hibernate-mapping>

<hibernate-mapping package="com.example.hibernate">
    <class name="Person" table="t_person">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <many-to-one name="idCard" unique="true"/>
    </class>
</hibernate-mapping>

        Session session = null;
        Transaction tx = null;
        try {
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            
            IdCard idCard = new IdCard();
            idCard.setCardNo("78383");
            
            Person person = new Person();
            person.setName("tom");
            person.setIdCard(idCard);
            
            session.save(person);
            tx.commit();
        }
        catch(Exception e) {
            e.printStackTrace();
            tx.rollback();
        }
        finally {
            HibernateUtils.closeSession(session);
        }