com.mycompany.celltableexmaple.server.GreetingServiceImpl.java Source code

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Here is the source code for com.mycompany.celltableexmaple.server.GreetingServiceImpl.java

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// -*- mode: java; c-basic-offset: 2; -*-
// Copyright 2013-2014 Vincent Zhang, All rights reserved
// Released under the MIT License: https://github.com/karuto/gwt-celltable/blob/master/mitlicense.txt
// Dependencies: Google App Engine SDK 1.8.3, GWT SDK 2.5.1

package com.mycompany.celltableexmaple.server;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.mycompany.celltableexmaple.client.CellTableExample.GalleryApp;
import com.mycompany.celltableexmaple.client.GreetingService;
import com.mycompany.celltableexmaple.shared.FieldVerifier;
import com.google.gwt.user.server.rpc.RemoteServiceServlet;

/**
 * The server side implementation of the RPC service.
 */
@SuppressWarnings("serial")
public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService {

    public String greetServer(String input) throws IllegalArgumentException {
        // Verify that the input is valid. 
        if (!FieldVerifier.isValidName(input)) {
            // If the input is not valid, throw an IllegalArgumentException back to
            // the client.
            throw new IllegalArgumentException("Name must be at least 4 characters long");
        }

        String serverInfo = getServletContext().getServerInfo();
        String userAgent = getThreadLocalRequest().getHeader("User-Agent");

        // Escape data from the client to avoid cross-site script vulnerabilities.
        input = escapeHtml(input);
        userAgent = escapeHtml(userAgent);

        return "Hello, " + input + "!<br><br>I am running " + serverInfo
                + ".<br><br>It looks like you are using:<br>" + userAgent;
    }

    /**
     * Escape an html string. Escaping data received from the client helps to
     * prevent cross-site script vulnerabilities.
     * 
     * @param html the html string to escape
     * @return the escaped string
     */
    private String escapeHtml(String html) {
        if (html == null) {
            return null;
        }
        return html.replaceAll("&", "&amp;").replaceAll("<", "&lt;").replaceAll(">", "&gt;");
    }

    /**
     * Grabbing data from gallery's remote server.
     * Note: the parameter start and length aren't used here.
     */
    public List<GalleryApp> getApps(int start, int length) {
        final String galleryURL = "http://usf-appinventor-gallery.appspot.com/rpc?tag=all:0:50";
        try {
            // Line below only valid at the server side. Cannot do it at client.
            URLConnection connection = new URL(galleryURL).openConnection();

            //connection.setRequestProperty("Accept-Charset", charset);

            // Capture the returned data from server.
            InputStream response = connection.getInputStream();
            java.util.Scanner s = new java.util.Scanner(response).useDelimiter("\\A");
            ArrayList<GalleryApp> list = parseAppList(s.next());

            return list;
        } catch (IOException e) {
            //return "exception opening gallery";
            return new ArrayList<GalleryApp>();
        }

    }

    /*
     * Helper method for parsing through JSON data, slicing up the workload.
     */
    public ArrayList<GalleryApp> parseAppList(String jsonStr) {
        ArrayList<GalleryApp> appList = new ArrayList<GalleryApp>();
        if (jsonStr == null || jsonStr.length() == 0)
            return appList;
        try {
            JSONObject o = new JSONObject(jsonStr);
            JSONArray results = (JSONArray) o.get("result");
            for (int i = 0; i < results.length(); i++) {
                JSONObject singleApp = results.getJSONObject(i);
                GalleryApp galleryApp = parseApp(singleApp);
                if (galleryApp != null)
                    appList.add(galleryApp);
            }
        } catch (JSONException e) {
            return appList; //need to do something here
        }
        return appList;
    }

    /*
     * Helper method that processes one app at a time.
     * Creates our GalleryApp object for ease of management.
     */
    public GalleryApp parseApp(JSONObject appJson) {
        try {
            String title = appJson.get("title").toString();
            String description = appJson.get("description").toString();
            String image1 = appJson.get("image1").toString();
            //String sourceFileName = appJson.get("sourceFileName").toString();

            GalleryApp galleryApp = new GalleryApp(title, description, image1);
            return galleryApp;
        } catch (JSONException e) {
            // TODO: Add better exception handling
            return null;
        }
    }

}