title: WSO2 set a property type is string but change to integer
body: <p>I set a property type is string as below:</p>
  
  <pre><code>&lt;property name="result" scope="default" type="STRING" value="0"/&gt;
   &lt;payloadFactory media-type="xml"&gt;
        &lt;format&gt;
          &lt;jsonObject&gt;
              &lt;result&gt;$1&lt;/result&gt;                             
           &lt;/jsonObject&gt;
        &lt;/format&gt;
        &lt;args&gt;
          &lt;arg evaluator="xml" expression="$ctx:result"/&gt;         
        &lt;/args&gt;
      &lt;/payloadFactory&gt;
  </code></pre>
  
  <p>But the response result is integer.What happened?</p>
  
  <pre><code>{
          "result": 0
  }
  </code></pre>