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Master the Jxta shell, Part 1

Gain hands-on Jxta experience with the interactive Jxta shell

By Navaneeth Krishnan, JavaWorld.com, 01/11/02

With many technology pundits hailing peer-to-peer computing as a key technology for tomorrow's Internet, many Java developers have started showing interest in Sun Microsystems' Jxta, a network computing platform that holds promise as an infrastructure for peer-to-peer development. Unfortunately, Jxta is still in its early development stages. With few applications and resources available, Jxta proves difficult for an average Java programmer to master.

Perhaps the easiest way to learn Jxta is by exploring the Jxta shell, possibly the most important Jxta application available today. In Part 1 of this two-part series, I will introduce you to the Jxta shell, its installation and configuration, and its simple commands. My intent is to help you get started right away with Jxta.

In Part 2, I will discuss the shell internals and explain how to extend the shell functionality to build complex shell applications. I assume that you have had at least a brief introduction to Jxta; if not, read my previous article, "The Jxta Solution to P2P" (JavaWorld, October 2001).

Jxta shell overview

The Jxta shell is an application built on top of the Jxta Java Binding, the Jxta reference implementation in Java. The shell serves three basic purposes:

1. It demonstrates how easily you can build a meaningful application on top of Jxta.
2. It acts as a valuable reference for developers on how to use the Jxta APIs. Whenever I am confused about the API usage, I refer to the shell source code and, more often than not, find my answer painlessly.
3. It serves as an environment where developers can directly interact with the Jxta platform without any programming. Thus, developers can get the concepts right even before they write any source code.

Developers interact with the shell through user commands called shell commands. The shell acts as an interpreter. First, the shell waits for a user command. Then, upon receiving the command, the shell executes it and waits for the next command. During the wait state, the shell displays a JXTA> prompt.

Now, don't be surprised if that sounds familiar; a Unix or DOS shell behaves similarly. As a matter of fact, the Jxta shell was intentionally designed to resemble the Unix shell so that most developers would be familiar with it right away. For the same reason, most shell commands resemble Unix commands as well. You will definitely notice these similarities as we proceed.

Obtain and install the Jxta shell

The first step is to get the shell running on your system. You need to download the shell from jxta.org. The shell comes with the Jxta demo, and the installable can be found in Resources.

Download the installable appropriate for your operating system. Note that Jxta uses JDK 1.3.1; hence, you need at least version 1.3.1 of the JRE (Java Runtime Environment) for Jxta to run on your system.

Once the download is complete, installation is pretty straightforward, with an InstallAnywhere wizard guiding you through the process. The default installation location is C:\Program Files\JXTA_Demo. Note that I use Windows NT as my operating system and hence use Windows conventions in this article; however you can easily find equivalents for other operating systems.

 

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