code: protected String getRequestData() throws ActivityException {
          String varname = getAttributeValue(REQUEST_VARIABLE);
          Object request = varname == null ? null : getParameterValue(varname);
  
          if (hasPreScript()) {
              Object ret = executePreScript(request);
              if (ret == null) {
                  // nothing returned; requestVar may have been assigned by script
                  request = getParameterValue(varname);
              }
              else {
                  request = ret;
              }
          }
          if (request == null)
              throw new ActivityException("Request data is null");
  
          if (request instanceof DocumentReference)
              request = getDocumentContent((DocumentReference)request);
          if (request instanceof String)
              return (String)request;
          else {
              VariableInstance varInst = getVariableInstance(varname);
              com.centurylink.mdw.variable.VariableTranslator translator = VariableTranslator.getTranslator(getPackage(), varInst.getType());
              if (translator != null) {
                  if (translator instanceof JavaObjectTranslator)
                      return request.toString();
                  if (translator instanceof DocumentReferenceTranslator)
                      return ((DocumentReferenceTranslator)translator).realToString(request);
                  else
                      return translator.toString(request);
              }
          }
  
          throw new ActivityException("Cannot handle request of type " + request.getClass().getName());
      }
docs: The method overrides the one from the super class and perform the followings:
  <ul>
  <li>It gets the value of the variable with the name specified in the attribute
  REQUEST_VARIABLE. The value is typically an XML document or a string</li>
  <li>It invokes the variable translator to convert the value into a string
  and then return the string value.</li>
  </ul>
  The method will through exception if the variable is not bound,
  or the value is not bound to a DocumentReference or String.