This rest of this tutorial uses the Hidden Frame example to explain how to develop Comet-enabled web applications. You can download the example from grizzly.dev.java.net at Hidden example download. From there, you can download a prebuilt WAR file as well as a JAR file containing the servlet code.
The Hidden Frame example is so called because it uses hidden IFrames. The example allows multiple clients to increment a counter on the server. When a client increments the counter, the server broadcasts the new count to the clients using the Comet technique.
The Hidden Frame example uses the long-polling technique, but you can easily modify it to use HTTP-streaming by removing two lines. See To Notify the Comet Handler of an Event and To Create a HTML Page That Updates and Displays the Content for more information on converting the example to use the HTTP-streaming technique.
See Deploying and Running a Comet-Enabled Application for instructions on how to deploy and run the example.
When you run the example, the following happens:
The index.html page opens.
The browser loads three frames: The first one accesses the servlet using an HTTP GET; the second one loads the count.html page, which displays the current count; and the third one loads the button.html page, which is used to send the POST request.
After clicking the button on the button.html page, the page submits a POST request to the servlet.