Web Services and JXTA: Companion Technologies JXTA and Web services have a lot in common. Take a detailed look at the communications platform behind each technology and see why JXTA is influencing the present and future of Java Web services. by Bradley S. O'Hearne

n the beginning, a computer was created. But it was not good for that computer to exist alone, and so another computer was created. Computers were fruitful and multiplied, and countless networks emerged. Of course there is quite a bit more to it than that, but as these networks have grown more complex, the software applications that utilize them have had to address these ever-changing complexities.

I can recall that only a very few years ago, the hottest technology that could be boasted on a software developer's resume was experience with "distributed applications," and frequently, this phrase was more descriptively listed as "enterprise distributed applications." But examine this phrase, and the word "enterprise" gives away our collective industry predisposition toward distributed development. Such development was still fairly confined within an enterprise. This phase was bound to be short-lived, as the increased interconnection of networks has made the individual network appear as a microscopic dot from the stratosphere of the Internet. Distributed development no longer pertains to a cozy meadow inside the enterprise split rail fence; rather, it is millions of square miles extending into parts unknown. Applications are now faced with complexities previously non-existent, and two very popular technologies have emerged to address these issues: Web services and JXTA (an acronym representing the word "juxtapose"), Sun Microsystem's open peer-to-peer (P2P) initiative.

Web services and JXTA address different problems, if only high-level design goals are considered, but a closer examination of their aims and architectures show there are more than cursory similarities between the two. These similarities bode well for those of us in the Java world, as the technological trifecta of Web services, JXTA, and J2EE will make the Java platform difficult to compete with.

Problem Domains
Web services and JXTA have emerged from ostensibly different problem domains. Web services seek to externalize and modularize application functionality as advertised services on the Internet. It follows then, that with the introduction of Web services, the scale of distributed applications are no longer merely intra-enterprise, but are inter-enterprise (though keep in mind, Web services can be implemented entirely within the scope of a single enterprise).

JXTA on the other hand, is a P2P technology, focused on efficient use of the Internet ecosystem's collective natural resources. The collective processing power connected to the Internet far surpasses that which is utilized, and both the use of bandwidth and navigation of information gravitate toward heavily beaten paths and congested repositories, respectively. Put simply, the common methods of addressing the Internet (centralized servers and datacenters, centralized search engines and portals) aren't scaling proportionately to the growth of the Internet, and P2P seeks to solve this by using the cooperation of peers to accomplish various behaviors (i.e. services). However, while the formally stated problem domains look dissimilar, consider the pragmatic challenges facing the goals of both Web services and JXTA. These challenges are:

1. Connect providers of services with consumers of like services, across an uncontained Internet.
2. Liberate the use of services from platform dependencies, such as operating systems, programming languages, and proprietary means of invoking procedures on remote hosts.

While the problem domains appear different, the major problems that must be solved by both Web services and JXTA are very similar. The answer lies in an open communications protocol, which both Web services and JXTA provide. An examination of the Web services and JXTA architectures will reveal that even under the microscope, Web services and JXTA share much in common.

Communication Architectures

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Introduction	Communication Architectures