Java Reference
In-Depth Information
In the following paragraphs, we will describe in detail the job of a J2EE application deployer.
A typical J2EE deployment may involve the configuration of the following:
• The root URL where the application is available to end-users
• The username, password and other data for connecting to databases
• Business configuration data that depend on the particular application domain
• The system users that will play the role of system administrators for the application
Let's get into the details of J2EE deployment.
A Java enterprise application is defined as a hierarchy of directories and files in a standard lay-
out. One type of these files, known as deployment descriptor files ,are essential in J2EE
deployment. They are XML files that describe how to package J2EE components into an appli-
cation. They provide structural and application assembly information.
Deployment descriptors are used in EJB JAR files as well as Web modules (packaged as WAR
files), with different syntax conventions. In turn, Web modules and EJB modules are packaged
together in application archives (EAR) files. Both EAR and WAR files are special JAR files
with a different suffix.
The deployer performs two activities on the assembled application:
•Installing the application that is copying it into the operational J2EE server, generating
container-specific classes and interfaces.
• Configuring the installed application. Analysis entities such as security roles defined by
the application assembler need to be mapped to user groups and accounts on the operat-
ing environment.
Another task is to ensure that all external dependencies are resolved.
Enterprise Java Bean Files
Enterprise Java Bean files are JAR files containing the following:
•Java class files and their home and remote interfaces
•Java class files for any classes and interfaces the enterprise bean code depends on, that
are not included in the EJB file
• The EJB deployment descriptor, usually named ejb-jar.xml ,in the META-INF directory
• The MANIFEST.MF standard manifest file in the META-INF directory
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