java.lang.ClassCastException: com.sun.proxy.$Proxy13 cannot be cast to sm.dao.UserDao

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
UserDao userDao = (UserDao) applicationContext.getBean("UserDao");

   ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
    IUserDao userDao = (IUserDao) applicationContext.getBean("UserDao");

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <bean id="dataSoure" class="org.apache.commons.dbcp.BasicDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
        <property name="url" value="jdbc:mysql://localhost:3306/sm"></property>
        <property name="username" value="root"></property>
        <property name="password" value="genji"></property>

    </bean>
    <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource">
            <ref bean="dataSoure"></ref>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">
                    org.hibernate.dialect.MySQL5Dialect

                </prop>
                <prop key="hibernate.current_session_context_class">
                    org.springframework.orm.hibernate4.SpringSessionContext
                </prop>


            </props>


        </property>
        <property name="mappingResources">


            <list>
                <value>sm/po/Studentinfo.hbm.xml</value>
                <value>sm/po/User.hbm.xml</value>
            </list>
        </property>


    </bean>
    <bean id="UserDao" class="sm.dao.UserDao">
        <property name="sessionFactory">
            <ref bean="sessionFactory"></ref>
        </property>


    </bean>
    <bean id="SinfoDao" class="sm.dao.SinfoDao">
        <property name="sessionFactory">
            <ref bean="sessionFactory"></ref>

        </property>


    </bean>
//就是在这里实现了事务代理

    <bean id="txManager"
          class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>
    <tx:annotation-driven />
    <tx:advice id="txAdvice" transaction-manager="txManager">
        <tx:attributes>
            <tx:method name="add" read-only="true" propagation="REQUIRED" />
            <tx:method name="read" propagation="REQUIRED" />
            <tx:method name="del" propagation="REQUIRED" />
            <tx:method name="mod" propagation="REQUIRED" />
            <tx:method name="sameId" propagation="REQUIRED" />
            <tx:method name="findUser" propagation="REQUIRED"/>
            <tx:method name="addUser" propagation="REQUIRED"></tx:method>
        </tx:attributes>
    </tx:advice>

</beans>