GWT EntryPoint JSON RPc

EntryPointTemplte.gwt.java

package com.lingona.rockgwt.front.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.RequestException;
import com.google.gwt.http.client.Response;
import com.google.gwt.json.client.JSONArray;
import com.google.gwt.json.client.JSONException;
import com.google.gwt.json.client.JSONObject;
import com.google.gwt.json.client.JSONParser;
import com.google.gwt.json.client.JSONValue;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.FlexTable;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.RootPanel;

public class Rockgwtfront implements EntryPoint {

    public void onModuleLoad() {
        final Button sendButton = new Button("Get Hendrix songs");
        final FlexTable songsTable = new FlexTable();

        // We can add style names to widgets
        sendButton.addStyleName("sendButton");
        
        sendButton.addClickHandler(new ClickHandler() {
            @Override
            public void onClick(ClickEvent event) {
                String hendrixSongsServiceUrl = GWT.getHostPageBaseURL();
                if(!GWT.getHostPageBaseURL().contains("rockgwt"))
                    hendrixSongsServiceUrl += "rockgwt/";
                    
                hendrixSongsServiceUrl += "hendrix/songs";
                RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, hendrixSongsServiceUrl);
                builder.setTimeoutMillis(10000);
                builder.setCallback(new RequestCallback() {
                    
                    @Override
                    public void onResponseReceived(Request request, Response response) {
                        if (response.getStatusCode() == 200) {
                            
                            JSONValue v = JSONParser.parse(response.getText());
                            JSONArray songs = v.isArray();
                            if(songs != null){
                                updateBacklogItemsTable(songsTable, songs);
                            }
                            else{
                                throw new JSONException("O retorno nao veio como um objeto de Projeto"); 
                            }
                        } else {
                            onError(request, new RequestException(response.getText()));
                        }
                    }
                    
                    @Override
                    public void onError(Request request, Throwable exception) {
                        Window.alert(exception.getLocalizedMessage());
                    }
                });
                try {
                    builder.send();
                } catch (RequestException e) {
                    Window.alert(e.getLocalizedMessage());
                }
            }
        });

        RootPanel.get("sendButtonContainer").add(sendButton);
        RootPanel.get("songsTableContainer").add(songsTable);

    }
    
    private void updateBacklogItemsTable(FlexTable songsTable, JSONArray songs) {
        songsTable.clear();
        for (int i=0; i<songs.size(); i++) {
            JSONObject item = songs.get(i).isObject();
            songsTable.setWidget(i, 0, new Label(item.get("name").isString().stringValue()));
            songsTable.setWidget(i, 1, new Label(item.get("album").isString().stringValue()));
        }
                    
    }
}