关于cxf客户端添加拦截器会报错呢？

具体代码如下：
WebServiceImp is = new WebServiceImp();
IwebService ws = is.getWebServiceImpPort();
Client client = ClientProxy.getClient(is);
报以下错误：

Exception in thread "main" java.lang.IllegalArgumentException: not a proxy instance
at java.lang.reflect.Proxy.getInvocationHandler(Proxy.java:637)
at org.apache.cxf.frontend.ClientProxy.getClient(ClientProxy.java:120)
at com.forest.test.client.imp.ClientMain.main(ClientMain.java:17)

若将代码改成
WebServiceImp is = new WebServiceImp();
IwebService ws = is.getWebServiceImpPort();
Client client = ClientProxy.getClient(is);
就报以下错误：
Exception in thread "main" java.lang.ClassCastException:
com.sun.xml.ws.client.sei.SEIStub cannot be cast to org.apac
he.cxf.frontend.ClientProxy
at org.apache.cxf.frontend.ClientProxy.getClient

        (ClientProxy.java:120)

at com.forest.test.client.imp.ClientMain.main(ClientMain.java:17)

求指点。谢谢