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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. In the Java Web Services Developer Pack (Java WSDP) Web components run in the Tomcat 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.

This chapter describes the organization, configuration, and installation and deployment procedures for Web applications. Chapters 10 and 9 cover how to develop Web components for service-oriented Web applications. Chapters 12 and 13 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.

In This Chapter

Web Application Life Cycle

Web Application Archives

WAR Directory Structure

Tutorial Example Directory Structure

Creating a WAR

Configuring Web Applications

Prolog

Alias Paths

Context and Initialization Parameters

Event Listeners

Filter Mappings

Error Mappings

References to Environment Entries, Resource Environment Entries, or Resources

Installing Web Applications

Deploying Web Applications

Listing Installed and Deployed Web Applications

Running Web Applications

Updating Web Applications

Reloading Web Applications

Redeploying Web Applications

Removing Web Applications

Undeploying Web Applications

Internationalizing and Localizing Web Applications

Accessing Databases from Web Applications

The Examples

Installing and Starting the Database Server

Populating the Database

Configuring the Web Application to Reference a Data Source

Defining a Data Source in Tomcat

Configuring Tomcat to Map the JNDI Name to a Data Source

Further Information

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This tutorial contains information on the 1.0 version of the Java Web Services Developer Pack.

All of the material in The Java Web Services Tutorial is copyright-protected and may not be published in other works without express written permission from Sun Microsystems.