I'm new in gwt. and need to know how to use JSON in gwt so i try this simple data loader but i'm still confuse.
I create a project named 'tesdb3' in eclipse. I create the PHP side to access the database, and made the output as JSON..
I create the userdata.php in folder war. then I compile tesdb3 project. Folder tesdb3 and the userdata.php in war moved in local server(I use WAMP). I put the PHP in folder tesdb3. This is the result from my localhost/phpmyadmin/tesdb3/userdata.php

[{"kode":"002","nama":"bambang gentolet"}{"kode":"012","nama":"Algiz"}]

From that result I think the PHP side was working good.
Then I create UserData.java as JSNI overlay like this:

package com.tesdb3.client;
import com.google.gwt.core.client.JavaScriptObject;

class UserData extends JavaScriptObject{ protected UserData() {}

  public final native String getKode() /*-{ return this.kode; }-*/;
  public final native String getNama()  /*-{ return this.nama;  }-*/;

  public final String getFullData() {
      return getKode() + ":" + getNama();
  }

}

Then Finally in the tesdb3.java:

public class Tesdb3 implements EntryPoint {

String url= "http://localhost/phpmyadmin/tesdb3/datauser.php";

private native JsArray<UserData> getuserdata(String Json)
/*-{ 
    return eval(json); 
}-*/;

public void LoadData() throws RequestException{
    RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, URL.encode(url));

    builder.sendRequest(null, new RequestCallback(){
        @Override
        public void onError(Request request, Throwable exception) {
            Window.alert("error " + exception);
        }

        public void onResponseReceived(Request request,
                Response response) {

            getuserdata(response.getText());
            //this is how i use the userdata json(is this already translated?)

            UserData UD = null;             
            String LKode =UD.getKode(); 
            String LName =UD.getNama();                 
            Label L = new Label(LKode+""+LName);
            RootPanel.get().add(L);
        }
    });
}

public void onModuleLoad() {        
    try {
        LoadData();
    } catch (RequestException e) {
        e.printStackTrace();
    }
}

}

The result is blank(i use development mode). and there was an eror like this:(I show it just some part)

10:46:29.984 [ERROR] [tesdb3] Uncaught exception escaped com.google.gwt.core.client.JavaScriptException: (ReferenceError): json is not defined fileName: http://localhost:1092 lineNumber: 2 stack: ("")@http://localhost:1092:2

My question is:
How I use the translated Json in right way??
Is there any wrong use from my code?
Is that necessary to move the compiled project to local server folder?(i do it following a tutorial from google).

Sorry too many ask. but i'm really really confused.