JAVA代理Proxy.newProxyInstance的疑问

[qq_41877186]

本人学习spring的Bean后处理器的时候，将Bean添加一个Proxy代理，结果出现java.lang.ClassCastException
具体异常如下：
java.lang.ClassCastException: com.sun.proxy.$Proxy2 cannot be cast to com.org.test02.UserDao
at com.org.test02.myTest.Test02(myTest.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

我在Bean后处理器的两个方法中加入代理，代码如下：

@Override
	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {

		Object proxy = Proxy.newProxyInstance(
							bean.getClass().getClassLoader(),
							bean.getClass().getInterfaces(),
							new InvocationHandler() {
								@Override
								public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
									// TODO Auto-generated method stub
									Object result = method.invoke(bean, args);
									if(result != null){
										return ((String)result).toUpperCase();
									}
									return result;
								}
							});
		return proxy;
	}

将代理当做Bean对象返回给测试类：

@Test
	public void Test02(){
		ApplicationContext ctx = new ClassPathXmlApplicationContext("com/org/test02/applicationContext.xml");
		UserDao dao = (UserDao) ctx.getBean("userDao");
//		dao.save();
		System.out.print(dao.save());
	}

下边是dao与实现类的代码：
UserDao.java

public class UserDao implements IUserDao {
	public UserDao(){
		
	}
	@Override
	public String save() {
		// TODO Auto-generated method stub
		System.out.println("----已经保存USER数据!----");
		return "aaaaaaaaaaaa";
	}

}

IUserDao.java:

public interface IUserDao {
	String save();
}

DEBUG了一下，发现创建代理的时候都没有出现异常，但是在执行new InvocationHandler()这里的时候不知道为什么debug没有进入到invoke方法中：

@Override
								public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
									// TODO Auto-generated method stub
									Object result = method.invoke(bean, args);
									if(result != null){
										return ((String)result).toUpperCase();
									}
									return result;
								}

但是也没有出现异常，异常发生在测试类的 UserDao dao = (UserDao) ctx.getBean("userDao");时候，请问各位前辈指点一下问题出在那里，谢谢。

[大寒Num1]

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