EXPERT RESPONSE
Welcome to acronym hell. Sometimes I wonder if this whole Java/J2EE thing
would have failed miserably, had it not been for the availability of the
A-R-chive acronym derivatives. As you breeze through literature and Web
sites that discuss Java and J2EE, you will see such acronyms as RAR, WAR,
JAR, EAR, and possibly even TAR. I predict that someday, Java and J2EE will
enable you to jump in a CAR, drive to the BAR, get in a WAR discussing PAR,
hit somebody with an OAR and then turn and run FAR. Where's my rimshot?
But seriously folks...even if you are unfamiliar with any of the other
extensions, you more than likely have encountered a file with a .jar
extension or a discussion of JAR files.
Files with a .jar extension or JAR files, are essentially just a collection
of files compressed using the ZIP/ZLIB compression format. JAR (short for
Java Archive) files were introduced in the early days of Java as a means to
conveniently package and distribute Java applications and components. Since
then, a number of additions to the Java platform have followed suit. The
introduction of the EAR file is one such addition.
An EAR (Enterprise Archive) file is a JAR file that contains a J2EE
application. A J2EE application is a group of Web modules that collectively
perform as a single entity. A Web Module is an entity consisting of one or
more resources such as HTML files, Java class files, XML files, etc. Web
Modules are packaged in Web Archive (WAR) files. Looking at it from a
top-down view, EAR files contain JAR files and WAR files. Packaging
resources in WAR files, JAR files and eventually EAR files, makes it easy to
reuse and reassemble components as new J2EE applications and distribute them
to new environments.
Tomcat is a servlet/JSP container available from the jakarta.apache.org
site. Tomcat deals only with WAR files. So, in order to auto-deploy a Web
application to a Tomcat environment, you must place an application's WAR
file in the appropriate directory or use Tomcat's deployment tools to
manually deploy the file. If you already have an EAR file that contains the
WAR file, you can extract the WAR file and use it as is. If you do not have
the EAR file or the WAR file, you can use any number of compliant tools to
create the WAR file. The following sites discuss the Tomcat deployment
process in detail:
Tomcat 3.x
Tomcat 4.x
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