What is JAX-RS (Java API for RESTful Web Services)?

(JAX-RS) - RESTful Web Services

Lightweight RESTful approaches have emerged as a popular alternative to SOAP-based technologies for deployment of services on the Internet. However, development of such services with the Java platform is significantly more complex than development of SOAP-based services, due to the low-level nature of the current platform APIs.

The goal of the Java API for RESTful Web Services (JAX-RS) is to provide a high-level declarative programming model for such services that is easy to use and encourages development according to REST tenets. Services built with this API are deployable with a variety of Web container technologies and benefit from built-in support for best-practice HTTP usage patterns and conventions.

For more details see the link below :

http://beta.parleys.com/#st=5&sl=10&id=264

What are the essential activities need to happen in any service-oriented environment

•Web service needs to be created, and its interfaces and invocation methods must be defined.
•Web service needs to be published to one or more intranet or Internet repositories.
•Web service needs to be located to be invoked by potential users.
•Web service needs to be invoked to be of any benefit.
•Web service may need to be unpublished when it is no longer available or needed.

Why do we need a Web Service?

Software applications written in various programming languages and running on various platforms can use web services to exchange data over computer networks like the Internet in a manner similar to inter-process communication on a single computer.

Web Service is:
•A collection of one or more functions/methods/software resources.
•Packaged as a single entity (encapsulate implementation details).
•Published on the network.
•Available for use by other programs, users and web services over the network.
Examples:
•Microsoft Passport authentication service.
•Stock Quote service.
•Credit checking service to obtain a persons credit information