[java] Returning JSON response from Servlet to Javascript/JSP page

I think (actually I KNOW!) I'm doing something wrong here I am trying to populate some values into HashMap and add each hasmap to a list which will be added to a JSON object:

JSONObject json = new JSONObject();
try
{
    Map address;
    List addresses = new ArrayList();

    int count = 15;

    for (int i=0 ; i<count ; i++)
    {
        address = new HashMap();
        address.put("CustomerName"     , "Decepticons" + i);
        address.put("AccountId"        , "1999" + i);
        address.put("SiteId"           , "1888" + i);
        address.put("Number"            , "7" + i);
        address.put("Building"          , "StarScream Skyscraper" + i);
        address.put("Street"            , "Devestator Avenue" + i);
        address.put("City"              , "Megatron City" + i);
        address.put("ZipCode"          , "ZZ00 XX1" + i);
        address.put("Country"           , "CyberTron" + i);
        addresses.add(address);
    }
    json.put("Addresses", addresses);
}
catch (JSONException jse)
{

}
response.setContentType("application/json");
response.getWriter().write(json.toString());

My problem is I know this is returning a string, which I cannot seem to parse (which is the problem). My question is how do I return the actual JSON encoded string (or even should I be doing this?) or what is the best method of attack for this type of problem. The JavaScript I am using for this is below:

function getReadyStateHandler(req)
{
    // Return an anonymous function that listens to the
    // XMLHttpRequest instance
    return function ()
    {
        // If the request's status is "complete"
        if (req.readyState == 4)
        {
            // Check that a successful server response was received
            if (req.status == 200)
            {
                msgBox("JSON Response recieved...");
                populateDatagrid(req.responseText.toJSON());
            }
            else
            {
                // An HTTP problem has occurred
                alert("HTTP error: " + req.status);
            }
        }
    }
}

Note the JSON Response comes back fine, but its a string. Any advice is greatly appreciated. I am also opening to using googles Gson, but don't have too much knowledge on that.

I think that what you want to do is turn the JSON string back into an object when it arrives back in your XMLHttpRequest - correct?

If so, you need to eval the string to turn it into a JavaScript object - note that this can be unsafe as you're trusting that the JSON string isn't malicious and therefore executing it. Preferably you could use jQuery's parseJSON

I used JSONObject as shown below in Servlet.

    JSONObject jsonReturn = new JSONObject();

    NhAdminTree = AdminTasks.GetNeighborhoodTreeForNhAdministrator( connection, bwcon, userName);

    map = new HashMap<String, String>();
    map.put("Status", "Success");
    map.put("FailureReason", "None");
    map.put("DataElements", "2");

    jsonReturn = new JSONObject();
    jsonReturn.accumulate("Header", map);

    List<String> list = new ArrayList<String>();
    list.add(NhAdminTree);
    list.add(userName);

    jsonReturn.accumulate("Elements", list);

The Servlet returns this JSON object as shown below:

    response.setContentType("application/json");
    response.getWriter().write(jsonReturn.toString());

This Servlet is called from Browser using AngularJs as below

$scope.GetNeighborhoodTreeUsingPost = function(){
    alert("Clicked GetNeighborhoodTreeUsingPost : " + $scope.userName );

    $http({

        method: 'POST',
        url : 'http://localhost:8080/EPortal/xlEPortalService',
        headers: {
           'Content-Type': 'application/json'
         },
        data : {
            'action': 64,
            'userName' : $scope.userName
        }
    }).success(function(data, status, headers, config){
        alert("DATA.header.status : " + data.Header.Status);
        alert("DATA.header.FailureReason : " + data.Header.FailureReason);
        alert("DATA.header.DataElements : " + data.Header.DataElements);
        alert("DATA.elements : " + data.Elements);

    }).error(function(data, status, headers, config) {
        alert(data + " : " + status + " : " + headers + " : " + config);
    });

};

This code worked and it is showing correct data in alert dialog box:

Data.header.status : Success

Data.header.FailureReason : None

Data.header.DetailElements : 2

Data.Elements : Coma seperated string values i.e. NhAdminTree, userName