Web services are self-contained, modular applications that you can describe, publish, locate, and invoke over a network.
WAS supports Web services that are developed and implemented based on the Web Services for J2EE specification.
A typical Web services scenario is a business application requesting a service from a given URL using SOAP messages over a Hypertext Transport Protocol (HTTP) or Java Messaging Service (JMS) transport. The service receives the request, processes it, and returns a response. Examples of a simple Web service include weather reports or getting stock quotes. The method call is synchronous, that is, it waits until the result is available. Transaction Web services, supporting quotes, business-to-business (B2B) or business-to-client (B2C) operations include airline reservations or purchase orders.
A Web service can be the service itself or the client that accesses the service.
Web services reflect a new, service-oriented architecture approach to programming. This approach is based on the idea of building applications by discovering and implementing network-available services, or by invoking available applications to accomplish some task. Web services deliver interoperability, for example, the ability for components created in different programming languages to work together as if they were created using the same language. Web services rely on existing transport technologies, such as HTTP, and standard data encoding techniques, such as Extensible Markup Language (XML), for invoking the implementation.
The key components of a Web service are...
WSDL is the XML-based file that describes the Web service and allows the Web service request to bind to the service.
SOAP is the XML-based protocol that allows the Web service request to invoke the service.
Web services are Webapplications that allow you to be more flexible in your business processes by integrating with applications that otherwise would not communicate. The inner-library loan program at your local library is a good example of the Web services concept and its evolution. The Web service concept existed even before the term; the concept exploded with the birth of the Internet. Before, you would visit your library, search the collections and check out your books. If you didn't find the book you wanted, the librarian did a search for you by computer or phone and located the book at a nearby library. The librarian ordered the book for you and you picked it up after it was delivered to your local library. By incorporating Web services applications, you can streamline your library visit. Now, you can search the local library collection and other local libraries at the same time. When other libraries provide your library with a Web service to search their collection (the service could have been provided through UDDI), your results yield their resources. Another Web service application might enable one to check the book out and get it sent to your home. Using Web services applications saves time and creates a convenience for you, as well as freeing the librarian to do other business tasks. For a more detailed scenario, see Web services scenario: Overview which tells the story of a fictional online garden supply retailer named Plants by WebSphere and how they incorporated the Web services concept.
Overview: Online garden retailer Web services scenarios
Web Services for J2EE
Web services: Resources for learning