Google App Engine Channel API

Question

I am trying to learn GAE\'s channel API (using Java), but I cannot figure out where to start from.

I went through Channel API Overview (Java) but the code posted there w

Answer 1

I'm new to StackOverflow and am not sure if this question is still open, but if you are still looking for a complete Java example using Google's Channel API, both ServerSide(Java) and Client(Java) you can find a detailed description I've written up here: http://masl.cis.gvsu.edu/2012/01/31/java-client-for-appengine-channels/

It lays out everything from creating a Channel(Client & Server), Sending a message on a channel (client & server) as well as a simple framework Java clients can utilize to interact with Channels. I too had a hard time understanding Google's Documentation and making sense of it all. I hope this information is still relavent and helpful :-)

The Complete Source Code and Chat Example can be found on GitHub: https://github.com/gvsumasl/jacc

Here's some sample code, I hope this helps :-)

---

Java Client Side Channel Creation (Using ChannelAPI Framework: Jacc)

ChatListener chatListener = new ChatListener();
ChannelAPI channel = new ChannelAPI("http://localhost:8888", "key", chatListener);
channel.open();

---

Java Server Side Channel Creation:

public class ChatChannelServlet extends HttpServlet {
  @Override
  public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {    
    String channelKey = req.getParameter("c");

    //Create a Channel using the 'channelKey' we received from the client
    ChannelService channelService = ChannelServiceFactory.getChannelService();
    String token = channelService.createChannel(channelKey);

    //Send the client the 'token' + the 'channelKey' this way the client can start using the new channel
    resp.setContentType("text/html");
    StringBuffer sb = new StringBuffer();
    sb.append("{ \"channelKey\":\"" + channelKey + "\",\"token\":\"" + token + "\"}");

    resp.getWriter().write(sb.toString());
  }
}

---

Java Client Message Sending (Using ChannelAPI Framework: Jacc)

/***
* Sends your message on the open channel
* @param message
*/
public void sendMessage(String message){
try {
        channel.send(message, "/chat");
    } catch (IOException e) {
        System.out.println("Problem Sending the Message");
    }
}

---

Java Server Side Message Sending:

public class ChatServlet extends HttpServlet {
  @Override
  public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String channelKey = req.getParameter("channelKey");
    String message = req.getParameter("message");

    //Send a message based on the 'channelKey' any channel with this key will receive the message
    ChannelService channelService = ChannelServiceFactory.getChannelService();
    channelService.sendMessage(new ChannelMessage(channelKey, message));
  }
}