Java Web Start is a mechanism for delivering and installing applications through a standard Web server. Initiated through the browser, these programs are deployed to the client and executed outside the scope of the browser. Once deployed, the programs do not need to be downloaded again, and they can automatically download updates on startup without requiring the user to go through the whole installation process again.
Since these programs run outside the browser, you might think they can freely perform operations - but that is not the case. They continue to run within a restricted container, or sandbox. Since Java Web Start runs on top of the Java 2 platform, programs are constrained by Java's underlying security architecture.
To use Java Web Start, you only need to install the client program (download web start).
To see Java Web Start in action, see Sun's Demonstration programs If you don't have Java Web Start already installed, clicking on the launch buttons of the of these programs will redirect you download page where you can download Web Start for your platform. Java Web Start itself is only about 1 MB. However, it requires the Java Runtime Environment (JRE), so if a you (or a user) don't have a JRE, the download size increases accordingly, to just under 6 MB on Microsoft Windows platforms.
If you experience problems launching the AstroGrid Workbench, first verify that you have Java Webstart correctly installed by running one of the demonstration programs.
On some platforms (especially Linux), it is necessary to configure Java Webstart to use your preferred web browser. Run javaws from a commandline to display the Webstart Console - from here you can alter configuration settings.
Occasionally a webstartable application may fail to start because it has become corrupted in some way. In this case, uninstall the application by opening the Java Webstart program (from the Start Menu, or by running javaws), and then selecting the application from the list.
To launch webstart applications from your web browser, the helper applications / file associations for the browser must be configured so that .jnlp files are handled by Java Webstart. The Webstart installer appears to do this for most modern browsers - Internet Explorer, Firefox, etc. For other browsers it may be necessary to do it by hand - google for examples.
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