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Introduction to web applications
A web application consists of servlets, JSPs, HTML pages, images, a standard
deployment descriptor, optionally, JavaBeans and custom tag classes, and other resources,
known as web components. You place these resources in a standard, predefined directory
structure so that you can deploy them on any web application server.
This section describes the important features and benefits of web applications.
The benefits of web applications
The Java Servlet 2.3 specification defines web applications. The specification offers the
following advantages:
Standard definition for representing a web application, including the application
directory structure and other information required for defining the application.
Standard definition for deploying a web application on an application server. A web
application written for an application server is guaranteed to be portable to any other
application server that adheres to the Java Servlet specification.
Relative links to reference application resources within the application. Because web
applications should not use absolute references, the location of an application on an
application server is not important. Therefore, you can deploy a web application in a
different directory or URL, or on a different server, from where it was developed.
JRun fully implements the web application architecture described in the Java Servlet 2.3
specification. You can develop a web application using JRun and deploy the application
on any other web application server that supports this specification. JRun also completely
supports the latest industry standards for developing enterprise-level J2EE applications,
so your web applications can take advantage of and interoperate with enterprise-level
J2EE resources and components.
Comparing web applications and enterprise applications
Enterprise applications are composed of one or more J2EE modules, typically web
applications, resource adapters, and EJBs. The standards for enterprise application
development on the web are based on the J2EE specification. JRun supports the J2EE
application model and provides a runtime environment for executing enterprise
applications.
An enterprise application also includes an enterprise application deployment descriptor,
application.xml, typically packaged in a single, compressed file called a Enterprise
ARchive (EAR) file.
For more information, see
A web application is a subset of an enterprise application. However, you can deploy
standalone web applications.
The configuration of a web application is defined by the contents of the web.xml file,
which is the standard web application deployment descriptor file. This file contains all
information required by an application server to execute the application.
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Chapter 6 Developing Web Applications
"Enterprise application architecture" on page
16.
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