Spring com.sun.proxy.$Proxy6 cannot be cast to

今天在带领学生做spring声明式事务时，部分同学的程序报错com.sun.proxy.$Proxy6 cannot be cast to。下面就详细介绍一下这个错误的原因及解决方法。

一、工程结构图

applicationContext.xml

<?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:context="http://www.springframework.org/schema/context"xmlns:aop="http://www.springframework.org/schema/aop" 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/context        http://www.springframework.org/schema/context/spring-context.xsd        http://www.springframework.org/schema/aop        http://www.springframework.org/schema/aop/spring-aop.xsd        http://www.springframework.org/schema/tx        http://www.springframework.org/schema/tx/spring-tx.xsd"><bean id="ds" class="com.mchange.v2.c3p0.ComboPooledDataSource"><property name="jdbcUrl" value="jdbc:oracle:thin:@192.168.1.104:1521:icss" /><property name="driverClass" value="oracle.jdbc.OracleDriver" /><property name="user" value="scott" /><property name="password" value="icss" /><property name="initialPoolSize" value="3" /><property name="maxPoolSize" value="10" /><property name="minPoolSize" value="1" /><property name="acquireIncrement" value="3" /><property name="maxIdleTime" value="60" /></bean><bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate"><property name="dataSource" ref="ds"></property></bean><bean id="userDaoImpl" class="dao.UserDaoImpl"><property name="jdbcTemplate" ref="jdbcTemplate"></property></bean><bean id="userServiceImpl" class="service.UserServiceImpl"><property name="user" ref="userDaoImpl"></property></bean><bean id="transactionManager"class="org.springframework.jdbc.datasource.DataSourceTransactionManager"><property name="dataSource" ref="ds"></property></bean><tx:advice id="txTransactionManager" transaction-manager="transactionManager"><tx:attributes><tx:method name="update*" isolation="DEFAULT" propagation="REQUIRED"read-only="false" /><tx:method name="delete*" isolation="DEFAULT" propagation="REQUIRED"read-only="false" /><tx:method name="insert*" isolation="DEFAULT" propagation="REQUIRED"   read-only="false" /><tx:method name="find*" read-only="true" /><tx:method name="read*" read-only="true" /><tx:method name="load*" read-only="true" /></tx:attributes></tx:advice><aop:config><aop:pointcut expression="within(service.*)" id="txPointCut"></aop:pointcut><aop:advisor advice-ref="txTransactionManager"pointcut-ref="txPointCut"></aop:advisor></aop:config></beans>

TestUser:

package config;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import service.IUserService;import service.UserServiceImpl;public class TestUser {/** * @param args */@Testpublic void insert(){ApplicationContext ac=new ClassPathXmlApplicationContext("config/applicationContext.xml");IUserService user=(UserServiceImpl) ac.getBean("userServiceImpl");user.insertBatch();}}

二、错误原因

       Spring AOP实现方式有两种，一种使用JDK动态代理，另一种通过CGLIB来为目标对象创建代理。如果被代理的目标实现了至少一个接口，则会使用JDK动态代理，所有该目标类型实现的接口都将被代理。若该目标对象没有实现任何接口，则创建一个CGLIB代理，创建的代理类是目标类的子类。

       显然，本工程中是通过JDK动态代理来实现AOP的。

三、解决方法

       1.在applicationContext.xml中增加下面内容，来强制使用CGLIB创建代理。

<strong><aop:aspectj-autoproxy proxy-target-class="true"/> </strong><aop:config><aop:pointcut expression="within(service.*)" id="txPointCut"></aop:pointcut><aop:advisor advice-ref="txTransactionManager"pointcut-ref="txPointCut"></aop:advisor></aop:config>

      2.ac.getBean("userServiceImpl")前强制类型改成接口

public void insert(){ApplicationContext ac=new ClassPathXmlApplicationContext("config/applicationContext.xml");IUserService user=<strong>(IUserService)</strong> ac.getBean("userServiceImpl");user.insertBatch();}