cxf创建webService报错，如何处理呢

public static void main(String[] args) {
        // TODO Auto-generated method stub
        JaxWsServerFactoryBean factory = new JaxWsServerFactoryBean();  
        factory.setAddress("http://localhost:8081/cxf");  
        factory.setServiceClass(HelloImpl.class);  
        Server server = factory.create();  
        server.start();  
    }

报错：Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/ws/WebServiceException at Main.main(Main.java:26)

为什么呢？

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try... catch...