Web Start could cache them without showing the related hooks in the UI. Therefore, fur-
ther attempts to launch the same application fail because Web Start incorrectly resorts to
cached (old) resources with unpredictable results. Advanced developers might selectively
purge the cache directly by deleting related files from the root directory showed in the
cache options area in the preferences panel.
• Launching the Java Web Start application from a command line and inspecting the
process' outputs can help in particularly nasty situations.
•Wandering around into the Java Web Start working directories and configuration files
(being careful not to damage anything) can help sometimes. However, remember that
undocumented configuration options are likely to be unsupported in future releases.
Finally, a great deal of information can be found at Sun's site, through documentation, discus-
sion newsgroups, and so forth.
In this chapter we introduced the JNLP technology through several examples. The proposed
examples are useful to illustrate the various features of JNLP and could serve as a basis for
creating your own deployment solutions.
• The first example (Listing 8.1) shows how to use JNLP with local files, without requiring
a web connection.
•Listing 8.4 shows a more detailed example that resemble closely a real application
launched through JNLP. It uses a web connection and some of the JNLP basic features.
•Listings 8.7 and 8.8 propose an application that is installed by a custom installer. The
code proposed in this example can be adapted to real-world custom installers.
The next two chapters will discuss the JNLP protocol more systematically and comprehen-
sively. In particular, Chapter 9 will deal with the structure of JNLP files and the main concepts
behind JNLP technology.