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Google AppEngine Java Channel API Basic Example
Hi all ,
Currently i’m working on Google App Engine with Channel API. I just needed basic socket example. I’ll show you how to create basic example.
Steps..
- Setup Eclipse Google App Engine Plugin
- Send Message From Servlet to Client
- Client Listener
- Deploy..
How to Install Google App Engine Eclipse Plugin
Note : When you downloading Eclipse choose the EE version. Check your Eclipse version under the eclipse directory in “.eclipseproduct”. If your version is under 3.8 you’ll be able to install from local archive. Please Check the plugin that corresponds to your version of Eclipse. I’m using Kepler 4.3: https://dl.google.com/eclipse/plugin/4.3
- Help->Install New Software add your location and install SDK. (I only need this for socket example)
- Restart Eclipse
- File->New->Web Application Project
- Done!!
Basic Java Servlet
Message Sender Servlet
package com.mtigdemir;
import java.io.IOException;
import javax.servlet.http.*;
import com.google.appengine.api.channel.ChannelMessage;
import com.google.appengine.api.channel.ChannelService;
import com.google.appengine.api.channel.ChannelServiceFactory;
@SuppressWarnings("serial")
public class ServletTest extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
ChannelService channelService = ChannelServiceFactory.getChannelService();
channelService.sendMessage(new ChannelMessage("logger", "Connection Testing.. "));
}
}
web.xml
<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<servlet>
<servlet-name>ServletTest</servlet-name>
<servlet-class>com.bumin.ServletTest</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ServletTest</servlet-name>
<url-pattern>/test</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>Logger.jsp</welcome-file>
</welcome-file-list>
</web-app>
Basic Client
Channel API Javascript Socket Listener
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.List" %>
<%@ page import="com.google.appengine.api.users.User" %>
<%@ page import="com.google.appengine.api.users.UserService" %>
<%@ page import="com.google.appengine.api.users.UserServiceFactory" %>
<%@ page import="com.bumin.model.Todo" %>
<%@ page import="com.bumin.dao.Dao" %>
<%@ page import="com.google.appengine.api.channel.ChannelService" %>
<%@ page import="com.google.appengine.api.channel.ChannelServiceFactory" %>
<%@page import="java.util.ArrayList"%>
<%
ChannelService channelService = ChannelServiceFactory.getChannelService();
String token = channelService.createChannel("logger");
%>
<!DOCTYPE html>
<html>
<head>
<script src='//code.jquery.com/jquery-1.7.2.min.js'></script>
<script src="/_ah/channel/jsapi"></script>
</head>
<body>
<script>
var token ="<%=token %>";// This will creaete unique identifier(some id created by google api + ur key)
channel = new goog.appengine.Channel('<%=token%>');
socket = channel.open();
socket.onopen = function() {$('#messages').append('<p>Connected!</p>'); };
socket.onmessage = function(message) {
console.log(message);
console.log('message' + message);
$('#messages').append('<p>' + message.data + '</p>');
};
socket.onerror = function() { $('#messages').append('<p>Connection Error!</p>'); };
socket.onclose = function() { $('#messages').append('<p>Connection Closed!</p>'); };
</script>
LOG Messages
<p id="messages"></p>
</body>
</html>
Sign In with your Google Account
Until you want to deploy your project to Google Server this step isn’t necesary. But live is better and also free until charge limits :))
- Before deploy your application check the 24 Hours App Engine Quotas for Channel API
Daily Quata limits can be change day by day
| Resource | Free Default Limit | Billing Enabled Default Limit | ||
|---|---|---|---|---|
| Daily Limit | Maximum Rate | Daily Limit | Maximum Rate | |
| Channel API Calls | 657,000 calls | 3,000 calls/minute | 91,995,495 calls | 32,000 calls/minute |
| Channels Created | 100 channels | 6 creations/minute | Based on your budget | 60 creations/minute |
| Channel Hours Requested | 200 hours | 12 hours requested/minute | Based on your budget | 180 hours requested/minute |
| Channel Data Sent | Up to the Outgoing Bandwidth quota | 22 MB/minute | 1 TB | 740 MB/minute |
- Right click your project Google-> Deploy to App Engine that’s it!!
Finally
Let’s run at local http://localhost:8888/Logger.jsp http://localhost:8888/test?message=mymessage open together.
You’ll see push notification when get the “/test” route. parameter is “message”There is my Live Application : http://1-dot-southern-branch-679.appspot.com/Don’t Forget the open http://1-dot-southern-branch-679.appspot.com/Logger.jsp
Muharrem Tığdemir
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