services should be described and bound by clients.
II. Universal Disc overy, Description and Integration (UDDI)

In order to use a service, a client must first locate that service and retrieve information to use the service.

The Universal Discover, Description and Integration or UDDI
specification, defines a number of lookup services that allow clients to look up and retrieve the required information to access a Web Service. UDDI provides a mechanism for clients to dynamically find other web services over the web. Using a UDDI interface, businesses can dynamically connect to services provided by external business partners.

UDDI actually provides three specific services:

• Traditional White Pages for looking up a Web Service by name.
• Traditional Yellow Pages for looking up a Web Service by topic.
• Green Pages for more generic searches based on the
characteristics of a Web Service.

Vendors who provide UDDI services typically operate a service known as a UDDI Business Registry, or UBR, which can be accessed to both publish and request information about a given Web Service.

III. Connecting It All Together With the Simple Object Access Protocol (SOAP)

We have analyzed few things like defining, describing and
publishing a web service. Now we see the mechanism to
access a web service once we’ve found it.

Web Services become accessible through the SOAP protocols. SOAP defines a way to perform remote procedure calls (RPCs) using HTTP as the underlying communication protocol. Typically, a SOAP call is packed as a body of an HTTP request. SOAP is simple, easy to implement, and well supported in the industry. Even a UDDI registry is accessed through well-defined SOAP calls.

SOAP supports both synchronous and asynchronous call semantics i.e. standard RPC as well as message-based. It can also be used with a variety of protocols other than HTTP.

A SOAP message is an ordinary XML document containing
the following elements:

• A required Envelope element that identifies the XML
document as a SOAP message
• An optional Header element that contains header information
• A required Body element that contains call and response

information
• An optional Fault element that provides information about
errors that occurred while processing the message

AN INTERACTIVE WEB SERVICE WORKING
WITH JAVA:

Google

The Google Web APIs service package contains

• GoogleSearch.wsdl - the WSDL description
• googleapi.jar - a client java API library

and provides three operations for the Google database:

• doGoogleSearch
• doGetCachedPage
• doSpellingSuggestion

Developing Web Services with Java

The few essential tools for Java Web Service development:

• Apache AXIS (Apache Extensible Interaction System)
I a Java-based implementation of SOAP+WSDL
II largely allows the programmer to forget these technologies
III typically used together with Tomcat
IV Highly recommended!

• Sun’s Java WSDP (Web Services Developer Pack)
I support for SOAP, WSDL, UDDI, ...
II JAX-RPC maps SOAP/WSDL to RMI (Java Remote
Method Invocations)
III Java API for XML Pack (the so-called JAX Pack)
IV the JSP Standard Tag Libraries (JSTL) API
V Java Secure Socket Extension (JSSE) API
VI Jakarta Tomcat Web container
VII the Ant build tool
VIII the UDDI-based registry server

• Open-Source Java EE 5-compliant application server :
Project GlassFish
I Will feature a major transition from Java WSDP.
II Java WSDP Pack will no longer be developed as a
discrete release vehicle for the Web services and XML
technologies.
III will provide latest state of development will be supported
that WSDP provides
IBM’s alpha Works’s EETK (Emerging Technologies Toolkit)
IV Support for SOAP, WSDL, UDDI and much more...