http://www.BlossomAssociates.net/igb/JavaWebStart.html
2006-11-10
Java Web Start is a way to start Java programs from the web. If you have some program like a word processor installed on your computer chances are you have an icon for it on your desktop. Double click the icon and the program starts. Java Web Start is a bit like that except that the icon is in a web page instead of your desktop (and you need just a single click).
Actually Java Web Start is Sun's implementation of JNLP (Java Network Launch Protocol). This is an open standard and is why the link you see on the web page will likely end with ".jnlp". This will be a small file that will specify to Java Web Start details about the program. Enough details so that JWS can make decisions about, download, and launch the program.
Whoah! Isn't that dangerous? There's computer viruses out on that there Internet. How can you trust a program launched from a web page? Actually, this is a very good question. Sun and the JNLP folks have given this quite a lot of thought. These programs are typically signed digitally. This signature ensures that the source of the program is who it says it is. It is up to you to decide whether or not you trust that source. More information can be had from the web. Try a web search for things like "JNLP Security". When I did so recently I got a pointer to Java 2 Platform Security which starts out with a section on Java Web Start security.
After you have run a JWS program from the web, it is (usually) available to you locally. A copy of it is put on your computer which you can invoke later from Java Web Start's launch panel instead of the original web page. To do so, you would start JWS launcher instead of the web browser. There you will find icons for all the JWS programs you've run before. Click on the one you want to run.
OK. That's it for this page. You were warned that it would be brief. Further details (and more) can be found starting at Sun's Java Web Start page.