Debugging Java Web Start

To be able to debug a JavaWS program, first of all find out what command is run when javaws runs. To do this, set the following environment variable:

JAVAWS_TRACE_NATIVE=1

Then, run javaws with any jnlp file:

javaws http://site/program.jnlp

This will display a dialog box which contains the command that Java is running. Give the dialog box focus, and, on Windows at least, hit CTRL-C to copy this into the clipboard. You can then add the usual debug parameters and run the command from the command line. What you may need to do is put quotes around some of the properties in the dialog box if your paths have spaces in them.