Programming Tutorials

J2EE Application Components

By: aathishankaran in Java Tutorials on 2007-02-20  

The J2EE runtime environment defines four application component types that a J2EE product must support:

Application clients are Java programming language programs that are typically GUI programs that execute on a desktop computer. Application clients offer a user experience similar to that of native applications, and have access to all of the facilities of the J2EE middle tier.

Applets are GUI components that typically execute in a web browser, but can execute in a variety of other applications or devices that support the applet-programming model. Applets can be used to provide a powerful user interface for J2EE applications. (Simple HTML pages can also be used to provide a more limited user interface for J2EE applications.)J2S

APPLICATION COMPONENTS

Servlets, JSP pages, filters, and web event listeners typically execute in a web container and may respond to HTTP requests from web clients. Servlets, JSP pages, and filters may be used to generate HTML pages that are an application's user interface. They may also be used to generate XML or other format data that is consumed by other application components. A special kind of servlet provides support for web services using the SOAP/HTTP protocol.

Servlets, pages created with the JavaServer Pages technology, web filters, and web event listeners are referred to collectively in this specification as "web components". Web applications are composed of web components and other data such as HTML pages. Web components execute in a web container.

A web server includes a web container and other protocol support, security support, and so on, as required by J2EE specifications.

• Enterprise JavaBeans™ (EJB) components execute in a managed environment that supports transactions. Enterprise beans typically contain the business logic for a J2EE application. Enterprise beans may directly provide web services using the SOAP/HTTP protocol.