title: can't set Struts2 result type to json
body: <p>I want to use json with Struts2. However, when I set the action return type to "json", I got "there is no result type defined for type 'json' mapped with name 'success'." Bellow is struts.xml file.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;!DOCTYPE struts PUBLIC
      "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
      "http://struts.apache.org/dtds/struts-2.0.dtd"&gt;
  &lt;struts&gt;
      &lt;constant name="struts.custom.i18n.resources" value="resource"/&gt;
  
      &lt;package extends="struts-default" name="test"&gt;
          &lt;action name="inputHandler" class="inputHandlerAction"&gt;
              &lt;result name="input"&gt;/index.jsp&lt;/result&gt;
              &lt;result&gt;/result.jsp&lt;/result&gt;
          &lt;/action&gt;
          &lt;action name="setLangHandler" class="com.sesoft.test.setLanguageHandler"&gt;
              &lt;result&gt;/index.jsp&lt;/result&gt;
          &lt;/action&gt;
  
          &lt;action name="Handler" class="com.sesoft.test.Handler"&gt;
              &lt;result&gt;/test2.jsp&lt;/result&gt;
          &lt;/action&gt;   
      &lt;/package&gt;
  
      &lt;package name="example" extends="json-default"&gt;
  
          &lt;action name="ajaxHandler" class="com.sesoft.test.AjaxHandler"&gt;
              &lt;result name="success" type="json" /&gt;
          &lt;/action&gt;
  
      &lt;/package&gt;
  &lt;/struts&gt;
  </code></pre>
  
  <p>Before I added the json Action, all other action performs fine. But after I added the json Action, the server failed to action with error code 503.</p>
  
  <p>libs I've added "jsonplugin-0.33.jar" to the lib directory.</p>