vaadin-framework/src/com/itmill/toolkit/demo/features/FeatureServerEvents.java

/* *************************************************************************
 
                               IT Mill Toolkit 

               Development of Browser User Intarfaces Made Easy

                    Copyright (C) 2000-2006 IT Mill Ltd
                     
   *************************************************************************

   This product is distributed under commercial license that can be found
   from the product package on license/license.txt. Use of this product might 
   require purchasing a commercial license from IT Mill Ltd. For guidelines 
   on usage, see license/licensing-guidelines.html

   *************************************************************************
   
   For more information, contact:
   
   IT Mill Ltd                           phone: +358 2 4802 7180
   Ruukinkatu 2-4                        fax:   +358 2 4802 7181
   20540, Turku                          email:  info@itmill.com
   Finland                               company www: www.itmill.com
   
   Primary source for information and releases: www.itmill.com

   ********************************************************************** */

package com.itmill.toolkit.demo.features;

import java.net.MalformedURLException;
import java.net.URL;

import com.itmill.toolkit.terminal.ExternalResource;
import com.itmill.toolkit.ui.*;

public class FeatureServerEvents extends Feature {

	protected String getTitle() {
		return "Server Events";
	}

	protected Component getDemoComponent() {
		OrderedLayout l = new OrderedLayout();

		l.addComponent(
			new Label(
				"<h3>Multiplayer GO-Game</h3><p>For demonstration, see GO-Game example application. The application implements a "
					+ "multi-player board game, where the moved by one player are immediately reflected to "
					+ "another player.</p>"
					+ "<p>Updating another players screen is totally automatic, and the programmed "
					+ "does not need to be avare when the refresh requests are sent to screen by the server. In "
					+ "web adapter the requests are passed through open HTTP-connection as java-script fragments "
					+ "that update the windows that need repainting.</p>",
				Label.CONTENT_UIDL));

		URL goUrl = null;
		try {
			goUrl = new URL(getApplication().getURL(), "../go/");
		} catch (MalformedURLException e) {
		}

		if (goUrl != null) {
			Link link = new Link("Start GO-Game", new ExternalResource(goUrl));
			link.setTargetName("gogame");
			link.setTargetBorder(Link.TARGET_BORDER_NONE);
			l.addComponent(link);
		}

		l.addComponent(
			new Label(
				"<h3>Chat example</h3><p>For some purposes it might be better to create your own "+
				"stream. The easiest way of creating a continuous stream for "+
				"simple purposes is to use StreamResource-class. See chat "+
				"example below, how this technique can be used for creation "+
				"of simple chat program.</p>",
				Label.CONTENT_UIDL));

		URL chatUrl = null;
		try {
			chatUrl = new URL(getApplication().getURL(), "../chat/");
		} catch (MalformedURLException e) {
		}

		if (goUrl != null) {
			Link link = new Link("Start chat", new ExternalResource(chatUrl));
			link.setTargetName("chat");
			link.setTargetBorder(Link.TARGET_BORDER_NONE);
			l.addComponent(link);
		}

		return l;
	}

	protected String getDescriptionXHTML() {
		return "<p>Millstone component framework supports both transactional and "
			+ "continuous terminals. This means that either the events from the "
			+ "terminal are sent together as transactions or the events are "
			+ "passed immediately when the user initiates them through the user "
			+ "interface. </p>"
			+ "<p>WebAdapter converts the Millstone applications to web-environment "
			+ "by transferring the events as HTTP-parameters and drawing the "
			+ "pages after the components have received and handled the events. "
			+ "In the web-environment the web browser is always the active party that "
			+ "starts the transaction. This is problematic when the server should "
			+ "notify the user about changes without HTTP-request initiated by the "
			+ "user.</p>"
			+ "<h3>WebAdapter Solution</h3>"
			+ "<p>Millstone solves the problem by combining component frameworks "
			+ "ability to automatically notify terminal adapter about all visual "
			+ "changes to HTTP-protocols ability to handle very long and slow "
			+ "page downloads. WebAdapter provides the web browser with "
			+ "possibility to keep special server command stream open all the time. "
			+ "All the visual updates that happen in components causes the "
			+ "WebAdapter to automatically creates JavaScript that updates the "
			+ "corresponding web browser window and to send the script immediately "
			+ "to browser for execution.</p>"
			+ "<p>The mechanism is fairly complicated, but using the mechanism in "
			+ "any Millstone application is trivial. Application just needs "
			+ "to make sure that WebBrowser opens a hidden iframe to location: "
			+ "<code>?SERVER_COMMANDS=1</code>.</p>"
			+ "<p>See the example of the usage on Demo-tab to get better understanding "
			+ "of the mechanism. If you read the example's source code, you will notice that "
			+ "the program does not contain any support for sending events to client, as "
			+ "it is completely automatic.</p>";
	}

	protected String getImage() {
		return "serverevents.jpg";
	}

}