What's wrong with my java SOAP code when I call the web service and return the right result in the web but return a null string in my code?

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Java

SOAP

webservice

Here is the web service:TraditionalSimplifiedWebService[^]
e,I input the parameter named sText 冯小刚,and it return the right result <string xmlns="http://webxml.com.cn/">馮小剛.But when I write the code,it return null.What's wrong with my code?

String endpoint="http://www.webxml.com.cn/WebServices/TraditionalSimplifiedWebService.asmx?wsdl";
				String namespaceurl="http://www.webxml.com.cn/";
				Service service = new Service();
				Call call = (Call) service.createCall();
				call.setTargetEndpointAddress(endpoint);
				 call.setOperationName("toTraditionalChinese"); 
	            call.addParameter("sText",XMLType.SOAP_STRING, ParameterMode.IN);
	             call.setUseSOAPAction(true);
	            call.setSOAPActionURI("http://webxml.com.cn/toTraditionalChinese");
				 call.setReturnType(XMLType.SOAP_STRING);
				String userID="";String sText="冯小刚";
				 Object[] obj = {sText};
				try {
					String result =(String)call.invoke(obj);
					System.out.println(result);
				} catch (RemoteException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}