Developing J2EE applications - IntelliJ IDEA in Action - page 371

IDEA provides extensive support to the J2EE architecture, including support for
servlets, JavaServer Pages ( JSP s), and Enterprise JavaBeans ( EJB s). IDEA 's support
goes far beyond just recognizing JSP syntax and the Servlet API ; it covers every-
thing from initial creation and editing of source files and content to building,
deploying, and real-time debugging of web applications.
IDEA has rich support for web applications embedded throughout all its tools
and features. IDEA 's web development support should appeal to servlet and JSP
developers of any skill level, whether you're architecting a large-scale J2EE appli-
cation or doing basic JSP markup.
To illustrate some of the points in this chapter, we'll extend the ACME Cur-
rency Converter by adding a simple web application front-end.

11.1 Working with web applications

Web applications are designed to run across a network and in the context of a web
browser, and the J2EE platform provides a strong foundation on which to build
these applications. Those based on the J2EE platform are typically implemented
using the Java Servlet and JavaServer Pages API s. In fact, a web application can be
thought of as a collection of libraries, Java classes, JSP files, and other resources
bundled together with a deployment descriptor that describes their use. Such an
application can be deployed to any J2EE -compliant server in the form of a web
application archive file (also known as a WAR file or a WAR ). The format of the
WAR file is part of the Java Servlet Specification; it's a standard JAR file with some
additional requirements.
A WAR file defines a provider-independent way of combining HTML , JSP s,
servlets, Java classes, and JAR s into a single deployable package. This vendor
neutrality is made possible through a standardized XML deployment descriptor
that controls such elements as servlet names and URL mappings. Once created,
the WAR file is deployed into an application server, which reads the deployment
descriptors and makes the application available.
Exploring the full extent of the servlet and JSP technologies is beyond the
scope of this book, and we're going to assume that you have some degree of
familiarity with those technologies. The following material will focus on IDEA 's
support for the working with J2EE web applications.

11.1.1 Understanding web modules

Simply put, a web module is a specific type of IDEA module that is designed to con-
tain a web application. By defining a web application inside a web module (as