Introduction to Web Applications

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Introduction to Web Applications

Stephanie Bodoff

A Web application is a dynamic extension of a Web server. There are two types of Web applications:

Presentation-oriented. A presentation-oriented Web application generates dynamic Web pages containing various types of markup language (HTML, XML, and so on) in response to requests.

Service-oriented. A service-oriented Web application implements the endpoint of a fine-grained Web service. Service-oriented Web applications are often invoked by presentation-oriented applications.

In the Java 2 Platform, Web components provide the dynamic extension capabilities for a Web server. Web components are either Java Servlets or JSP pages. Servlets are Java programming language classes that dynamically process requests and construct responses. JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content. Although servlets and JSP pages can be used interchangeably, each has its own strengths. Servlets are best suited to service-oriented Web applications and managing the control functions of a presentation-oriented application, such as dispatching requests and handling nontextual data. JSP pages are more appropriate for generating text-based markup such as HTML, SVG, WML, and XML.

Web components are supported by the services of a runtime platform called a Web container. The Web container provides services such as request dispatching, security, concurrency, and life cycle management. It also gives Web components access to APIs such as naming, transactions, and e-mail.

Certain aspects of Web application behavior can be configured when the application is deployed to the Web container. The configuration information is maintained in a text file in XML format called a Web application deployment descriptor. A deployment descriptor must conform to the schema described in the Java Servlet specification.

This chapter describes the organization, configuration, and installation and deployment procedures for Web applications. Chapters 9 and 10 cover how to develop Web components for service-oriented Web applications. Chapters 3 and 4 cover how to develop the Web components for presentation-oriented Web applications. Many features of JSP technology are determined by Java Servlet technology, so you should familiarize yourself with that material even if you do not intend to write servlets.

Most Web applications use the HTTP protocol, and support for HTTP is a major aspect of Web components. For a brief summary of HTTP protocol features see HTTP Overview.

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