Java Web Start: Difference between revisions

Revision as of 10:20, 5 January 2009

Revision as of 21:23, 5 January 2009

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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 fassionfashion 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 refered to by this file (images, css), and finally renderesrenders 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 afterwoodsafterwords 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.

== Signed WebStartWeb Start applications ==

By default, Java webstartWeb Start applications run restricted, which means that they do not have access to some system resources such as local files. But end-users can remove these restrictions by signing their webstartWeb Start applications with the <code>jarsigner</code> tool that comes with the JDK.

== Well-known applications ==

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* [[CrossFTP]] &ndash; a user friendly FTP client and server

* [[PowerTeacher]] &ndash; a gradebook program for student scores as part of the larger student information system used by schools called [[PowerSchool]].

* [[DataReport Tool]] &ndash; A Java Web Starta tool developed by Caprion Proteomics for viewing, analyzing and filtering through a set of differentially expressed proteins

* [http://www.playclockwiser.com Clockwiser] &ndash; a free puzzle game designed to prevent your brain from melting in the witches' cauldron of the daily routine

== See also ==