Web Services

A web service is a collection of protocols and standards used for exchanging data between applications over the web. Web services enable applications written with different programming languages supported over varying platforms (different hardware, software, database, or network platforms) to exchange data, very conveniently.

Web services are a new breed of web technologies that offer a platform and language-neutral approach. They are so cool that a web service written in Java and running on BEA WebLogic server can access a web service written in C and running on a Microsoft IIS. All without a concern about, how each web service is actually implemented.
Web Services have revolutionized the way; the Business
to Business and Business to Consumer services are provided because they provide multiple functions, ranging from a simple web request to a complicated business process.

A web service makes it easily available over the web and uses a standardized XML messaging system as its core mechanism. XML is used to encode all communications into a web service. For example, a client invokes a web service by sending an XML message, then waits for a corresponding XML response. Because all communication is in XML, web services are not tied to any one operating system or programming language. So Java can talk with Perl and windows applications can talk with Unix applications

Web Services: Distributed Computing environment

Web Services have gradually evolved from the basic Remote Procedure Calls. But unlike RPCs they use XML as a core ingredient for communication. Web Service concerns about three specific things:

• A mechanism to find and register a service.
• A transport mechanism to access a service.
• A mechanism for two parties to communicate and define
the input-output parameters for a service.

What are Web Services

These properties, when coupled together, provide a new form of Distributed Computing Environment. It requires standard definition mechanisms, lookup services, and transport definitions using protocols like SOAP. These all are provided without concern for the underlying implementation mechanism.


Distributed Computing Environment: web scenario

Service provider: First and foremost a service provider is required to host any number of exposed Web Services.
Service repository: Secondly, a centralized service repository is required for publishing information that clients can use to find information about published Web Services.
And finally, various mechanisms are required to locate and
access the services.

Let’s look at the figure in general and understand what’s going on.
• Firstly, a service provider publishes a service to an external repository. Once such a service has been exported to a registry, it can then be used by a client.

• Client look- ups a service from a repository and receives
information about a service. Information, such as the format of the procedure calls and the address of a service provider, would normally be provided, amongst other details.

• At last, the client is bind to the underlying services and
then accesses that service (functionality the service

Web Services: Core specifications

XML: a key player: Web Services at its core uses a fundamental set of functionality based on XML (it is a wonderful technology, and it has really found a home in Web Services). XML provides a user-defined meta language that represents data and the sets of validating rules. XML has become an excellent vehicle for packing data over the distributed network such that both ends of the pipe easily exchange and understand the data.

XML provides a meta language in which you can write specialized languages to express complex interactions between clients and services. Behind the facade of a web server, the XML message gets converted to a middleware request and the results are converted back to XML.

July 2007 | Java Jazz Up | 35
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