Chapter 24 describes how to automate this build process.
Chapter 25 details how to sign the output JARs and how to export for use in Java Web Start scenarios.
The Lopica project (http://lopica.sourceforge.net) contains a wealth of information about Java Web Start.
The standard Java documentation (http://java.sun.com/j2se/1.4.2/docs) includes documentation on jarsigner and Java Web Start.