Java Web Start: Difference between revisions

Revision as of 09:46, 20 January 2009

Revision as of 19:57, 16 February 2009

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<!-- Deleted image removed: [[Image:Apple Java Web Start.png|left|80px]] -->

In [[computing]], '''Java Web Start''' (also known as '''JavaWS''' or as '''javaws'''), a [[Software framework | framework]] developed by [[Sun Microsystems]], allows users to start [[application software]] for the [[Java Platform]] directly from the [[Internet]] using a [[web browser]]. Unlike [[Java applet]]s, Web Start applications do not run inside the browser, and the [[sandbox (computer security)|sandbox]] in which they run need not have as many restrictions, although this can be configured. Web Start has an advantage over applets in that it overcomes many compatibility problems with browsers' Java [[plugin]]s and different [[Java virtual machine|JVM]] versions. On the other hand, Web Start programs cannot communicate with the browser as easily as applets. To assist migration, users can also invoke a Java Applet as a Java Web Start application.

Web Start provides a series of classes in the <code>[http://java.sun.com/products/javawebstart/docs/javadoc/index.html javax.jnlp]</code> [[Java package|package]] which provide various services to the application. Sun designed most of these services with the aim of allowing carefully controlled access to resources (such as files and the system clipboard) while restricting the application to authorized operations.

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Any computer user can use JNLP by simply installing a JNLP client (most commonly Java Web Start). The client installation can occur automatically, so that the end users can see the client launcher downloading and installing before the Java application the first time they launch the latter.

JNLP works in a similar fashion to how HTTP/HTML works for the web. For rendering a HTML webpage, after the user clicks on a weblink, the browser submits a URL to a webserver, which replies with a HTML file. The browser then requests the resources referedreferred to by this file (images, css), and finally renders the page once enough information has been retrieved. The page is usually rendered before all resources have been retrieved; some resources not critical to the layout of the page (images), can be retrieved afterwords or on request should 'Load Images Automatically' browser setting be unset.

This process is mirrored for JNLP; in the same way that a Web browser renders a webpage, a JNLP client 'renders' a Java app. After the user clicks on a weblink the browser submits a URL to a webserver, which replies with a JNLP file (instead of a HTML file) for the application. This file is parsed by the JNLP client, which then requests the resources referenced by this(jar files), and then launches the application once all required resources have been retrieved. Some resources can be marked 'lazy' within the JNLP file, which informs the JNLP client that the application does not need those resources to start, but can be retrieved later on when/if the application requests them.

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== Well-known applications ==

* [http://www.kaijudoportal.com/online Kaijudo Portal] &ndash; an online platform for playing the [[Duel Masters Trading Card Game]] in [http://www.kirricorp.net/ KirriCorp] and [http://dm.takaratomy.co.jp/ Japanese] formats.

* [[Wurm Online]] &ndash; a 3D Massively Multiplayer Online Fantasy Simulator.

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== References ==

{{reflist}}

<div class="references-small">

<references />

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== External links ==

* [http://java.sun.com/products/javawebstart/ Sun's Java Web Start product page]

* [http://java.sun.com/developer/technicalArticles/Programming/jnlp/ Deploying Software with JNLP and Java Web Start]