AXIS, the Apache eXtensible Interaction System, is an open source Web services toolkit developed by the Apache Software Foundation. It provides tools to serve two primary purposes: (1) Writing client Java programs that use Web services and (2) deploying Java programs as Web services.

While Microsoft .NET and Microsoft SOAP Toolkit are the two most widespread systems used to access SOAP, AXIS is the most commonly used SOAP implementation for Java. It is currently used by various commercial and open source products, including Borland Enterprise Server, Borland JBuilder, IBM's Emerging Technologies Toolkit (ETTK)/Web Services Toolkit (WSTK), JBoss, and Macromedia's Jrun.

This free solution, which is essentially Apache SOAP 3.0, was intended to create a more modular, more flexible and better performing implementation of SOAP (when compared to Apache SOAP 2.0). Built from scratch on entirely new foundations, its architecture extends and improves the functionality of Apache SOAP in the following ways:

Component-oriented deployment. AXIS introduces the concept of handlers for implementing common patterns of processing for applications.

Flexibility. AXIS facilitates the insertion of new extensions into the engine for custom header processing and system management. To achieve this, AXIS provides a WSDD which describes various components like handler objects, serializers and deserializers. The client application can then use this WSDD to deploy a Web service.

Improved interoperability. Relative to Apache SOAP 2.0, AXIS has better interoperability with the other SOAP implementations on the market. As an example, AXIS can process SOAP messages with untyped parameters generated by the MS-SOAP implementation.

Speed. While Apache SOAP used DOM (Document Object Model) to parse XML streams, AXIS uses SAX (Simple API for XML), which enables memory usage to be significantly reduced, and cuts the time required to process large XML documents. 

Support for other protocols. AXIS's architecture supports interchangeable transport protocols. SOAP senders and listeners now have the ability to add support for various other protocols such as SMTP and FTP.

On the fly WSDL support. One of the important new features of AXIS is its "on the fly" support for WSDL. AXIS is able to instantly generate WSDL descriptions of deployed services. Additionally, it implements the Java/WSDL mapping functionality of the JAX-RPC API. As a result, AXIS can generate a Java client by simply parsing the WSDL description of a service, or even generate a WSDL description for a Java class so it can be published as a Web service.

If you need to write Java programs that use Web services or deploy Java programs as Web services, and are looking for an open source toolkit, give Apache AXIS a try. Find out for yourself why it's quickly becoming the favorite tool for working with Web services in Java.