As we saw from the examples in the previous chapter, there are a few simple concepts associ-
ated with the JNLP technology. We will examine many of them in detail here in this chapter,
while leaving those related to the client environment definition (refer to Chapter 2, “An
Abstract Model for Deployment”) for Chapter 10, “Defining the Client Environment.”
Let's introduce the principal concepts we will see in this chapter.
• Resources . With this term are gathered together four types of objects: system properties,
extensions, native libraries, and of course, application JAR files. We will cover them in
• Descriptors . Every JNLP file is a descriptor, describing the type and attributes of the
pieces to be assembled together on the client platform. There are conceptually two kinds
of descriptors and four different JNLP descriptors.
• Extension Descriptors . In JNLP terminology, extensions are either installers (that is, Java
code run only once for installing particular executables) or components (that is, reusable
groups of JAR files needed for the application being launched).
• Application Descriptors . There are two types of application descriptors: applet and appli-
Figure 9.1 clarifies the role of extension and application descriptors regarding the basic struc-
ture (what a JNLP file basic syntax looks like).
is made of
Could be one of
F IGURE 9.1
Basic static structure of JNLP files.