Writing a Soap webservice method that takes an xml payload

Question

I have written a webservice with a method which takes a String as parameter as follows.

@WebService(targetNamespace = "http://bla.com", name = "MyWebService")  
@SOAPBinding(style = SOAPBinding.Style.DOCUMENT)
public interface MyWebService {

    boolean submitAssessmentResult(@WebParam(name = "resultXml") String resultXml);

The parameter for my message is supposed to be an xml string. For my test I just print the string out to the console. When I test the webservice using soapui and I call the method using a plain string like "This is a test" as follows then the test gets printed out perfectly:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:bla="http://bla.co.za/"&gt;
   <soapenv:Header/>
   <soapenv:Body>
      <shl:submitAssessmentResult>
         <resultXml>This is a test</resultXml>
      </shl:submitAssessmentResult>
   </soapenv:Body>
</soapenv:Envelope>

but if I call the method with an xml string then I get white space on the console:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:bla="http://bla.co.za/"&gt;
   <soapenv:Header/>
   <soapenv:Body>
      <shl:submitAssessmentResult>
         <resultXml>
           <AssessmentResult>bla</AssessmentResult>
         </resultXml>
      </shl:submitAssessmentResult>
   </soapenv:Body>
</soapenv:Envelope>

Does anyone know why my webservice is not recognising an xml payload