Introduction to web services and XML - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 581

Discovery and Integration (UDDI) directory service to register and look up web
services, and the Web Services Description Language (WSDL) to define and
describe a web service [12-14].
Another very popular technology for implementing web services in Java is
the Java API for XML-based RPC (JAX-RPC) [15]. In JAX-RPC, calling a web
service is handled much like a remote method call in RMI except the transport
mechanism used is HTTP.
We 've only scratched the surface of web services. In fact, we've only scratched
the surface of Java servlets. The technologies involved are not difficult to under-
stand or use, but they are many. We do not have the space in this topic to provide
real working examples, partly because setting up and configuring a web server
and servlet container such as Tomcat and loading servlets into it is a task that
requires much explanation.
The JWSDP provides many of these technologies in one convenient download.
There is also a very complete JWSDP Tutorial available. See the references for
further information about all these technologies.
21.6 Conclusion
Java clearly offers a diversity of resources and techniques for distributed com-
puting. In Chapter 14 we showed how to create a basic web server with low-
level socket code to connect with and send HTML data to browsers and cus-
tom clients. Chapter 15 looked at how to use sockets to pass data back and forth
directly between custom built servers and clients. In Chapters 16-20 we switched
to building programs on the RMI and CORBA frameworks in which objects can
invoke methods in other objects across a network just as if the objects were local.
With web services we return to a web server type scheme but at the higher level of
servlets and XML documents. Each of these approaches to distributed computing
has its advantages and disadvantages, and you can choose the one that best serves
a particular application.
21.7 Web Course materials
The Web Course provides further discussion of web services techniques and
includes an example that illustrates development of a servlet and a custom XML
format.
References
[1] Web services information available at www.w3.org/2002/ws , http://java.sun.
com/webservices , and http://msdn.microsoft.com/webservices .
[2] XML, www.w3.org/XML .
[3] Java and XML Tutorial, http://java.sun.com/xml .
[4] XML Namespaces, www.w3.org/TR/xml-names11/ .