spring jpa 测试时报错：java.lang.ClassCastException: com.sun.proxy.$Proxy20 cannot be cast to com.pp.dao.

报错详细：

java.lang.ClassCastException: com.sun.proxy.$Proxy20 cannot be cast to com.pp.dao.account.AccountDaoImpl
	at com.pp.tt.T1.testUpdate(T1.java:42)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	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.runNotIgnored(BlockJUnit4ClassRunner.java:79)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
	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:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

报错原因：

       在测试类时 ，获取bean时 ，强制类型为实现类

  

  public void testjpa(){
		ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml");
		daoImpl=(AccountDaoImpl) applicationContext.getBean("accountDao");
		List<Account> accounts=daoImpl.getList("select o from Account o");
		System.out.println(accounts.size());
		for(Account account:accounts){
			System.out.println(account.getName());
		}
		System.out.println("-----------------");
		System.out.println(daoImpl.getAccountById(1));
		System.out.println("-----------------");
		Account account=daoImpl.getAccountById(1);
		System.out.println(account.getPwd());
   }

解决方法：

           把获取的bean强制类型改为接口类型

		daoImpl=(AccountDao) applicationContext.getBean("accountDao");