Java Reference
In-Depth Information
• A functional component or components, such as an enterprise bean, web page, ser-
vlet, or applet
• An optional deployment descriptor that describes its content
Once a Java EE unit has been produced, it is ready to be deployed. Deployment typically
involves using a platform's deployment tool to specify location-specific information, such
as a list of local users who can access it and the name of the local database. Once deployed
on a local platform, the application is ready to run.
Packaging Applications
A Java EE application is delivered in a Java Archive (JAR) file, a Web Archive (WAR)
file, or an Enterprise Archive (EAR) file. A WAR or EAR file is a standard JAR (
.jar
)
file with a
.war
or
.ear
extension. Using JAR, WAR, and EAR files and modules
makes it possible to assemble a number of different Java EE applications using some of
the same components. No extra coding is needed; it is only a matter of assembling (or
packaging) various Java EE modules into Java EE JAR, WAR, or EAR files.
An EAR file (see
Figure 1-6
) contains Java EE modules and, optionally, deployment
descriptors. A
deployment descriptor
, an XML document with an
.xml
extension, de-
scribes the deployment settings of an application, a module, or a component. Because
deployment descriptor information is declarative, it can be changed without the need to
modify the source code. At runtime, the Java EE server reads the deployment descriptor
and acts upon the application, module, or component accordingly.
