Passing JSON object from Controller to View(jsp)

I am trying to send JSON object to my view from controller but unable to send it. Please help me out!

I am using following code

public class SystemController extends AbstractController{

    protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView mav = new ModelAndView("SystemInfo", "System", "S");

        response.setContentType("application/json;charset=UTF-8");
        response.setHeader("Cache-Control", "no-cache");
        JSONObject jsonResult = new JSONObject();

        jsonResult.put("JVMVendor", System.getProperty("java.vendor"));
        jsonResult.put("JVMVersion", System.getProperty("java.version"));
        jsonResult.put("JVMVendorURL", System.getProperty("java.vendor.url"));
        jsonResult.put("OSName", System.getProperty("os.name"));
        jsonResult.put("OSVersion", System.getProperty("os.version"));
        jsonResult.put("OSArchitectire", System.getProperty("os.arch"));

        response.getWriter().write(jsonResult.toString());
     //   response.getWriter().close();

        return mav;             // return modelandview object
    }
}

and in the view side I am using

<script type="text/javascript">

Ext.onReady(function(response) {
     //Ext.MessageBox.alert('Hello', 'The DOM is ready!');
     var showExistingScreen = function () {
        Ext.Ajax.request({
            url                     : 'system.htm',
            meth开发者_如何转开发od                  : 'POST',
            scope                   : this,
            success: function ( response ) {
                alert('1');
                var existingValues = Ext.util.JSON.decode(response.responseText);
                alert('2');
              }
        });
    };

    return showExistingScreen();
});

---

For sending JSON back to the client I successfully use the following solution:

1) client (browser) sends an AJAX POST containing JSON formatted values (but GET also possible) request to my SpringMVC controller.

$.postJSON("/login", login, function(data)
{
    checkResult(data);
});

2) The SpringMVC controller method signature:

@RequestMapping(value = "/login", method = RequestMethod.POST)
public @ResponseBody Map<String, String> 
login(@RequestBody LoginData loginData, 
HttpServletRequest request, HttpServletResponse response)

@ResponseBody is the key, it "...indicates that the return type should be written straight to the HTTP response body (and not placed in a Model, or interpreted as a view name)." [Spring Reference Doc] LoginData is a simple POJO container for the JSON values from the client request, filled automatically if you put a jackson jar file (I use jackson-all-1.7.5.jar) into your classpath. As result of the controller method, I create a hashMap<String, String>. (e.g. with keys 'error' or 'view' and appropriate values). This map is then automatically serialized into JSON which is interpreted by the client (again normal html page incl. Javascript)

function checkResult(result)
{
    if (result.error)
    {
      // do error handling
    }
    else
    {
      // use result.view
    }
}