Web Application Life Cycle

Web Application Life Cycle

A web application consists of web components, static resource files such as images,and helper classes and libraries. The web container provides many supporting services thatenhance the capabilities of web components and make them easier to develop. However,because a web application must take these services into account, the process forcreating and running a web application is different from that of traditional stand-aloneJava classes.

The process for creating, deploying, and executing a web application can be summarizedas follows:

1. Develop the web component code.

2. Develop the web application deployment descriptor.

3. Compile the web application components and helper classes referenced by the components.

4. Optionally package the application into a deployable unit.

5. Deploy the application into a web container.

6. Access a URL that references the web application.

Developing web component code is covered in the later chapters. Steps 2 through4 are expanded on in the following sections and illustrated with a Hello,World-style presentation-oriented application. This application allows a user to enter a name intoan HTML form (Figure 3-3) and then displays a greeting after the nameis submitted (Figure 3-4).

Figure 3-3 Greeting Form

Figure 3-4 Response

The Hello application contains two web components that generate the greeting and theresponse. This chapter discusses two versions of the application: a JSP version calledhello1, in which the components are implemented by two JSP pages (tut-install/javaeetutorial5/examples/web/hello1/web/index.jsp andtut-install/javaeetutorial5/examples/web/hello1/web/response.jsp) and a servlet version calledhello2, in which the components are implementedby two servlet classes (tut-install/javaeetutorial5/examples/web/hello2/src/servlets/GreetingServlet.java andtut-install/javaeetutorial5/examples/web/hello2/src/servlets/ResponseServlet.java). The two versions are usedto illustrate tasks involved in packaging, deploying, configuring, and running an application thatcontains web components. The sectionChapter 2, Using the Tutorial Examples explains how to get the code for theseexamples.

After you install the tutorial bundle, the source code for the examples isin the following directories:

• tut-install/javaeetutorial5/examples/web/hello1/

• tut-install/javaeetutorial5/examples/web/hello2/

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