JAR FILES Java Help

JAR FILES

Before developing your own Bean, it is necessary for you to understand JAR (Java
Archive) files, because tools such as the BDK expect Beans to be packaged within JAR  files. A JAR file allows you to efficiently deploy a set of classes and their-associated resources, For example,a developer may build a multimedia application that Uses various sound and image files. A set of Beans can control how and when this information is presented: All of these pieces can be placed into one JAR file. JAR technology makes it much easier to deliver and install software. Also, the elements in a JAR file are compressed, which makes downloading a JAR file much faster than separately downloading several uncompressed files, Digital signatures may also be associated with the individual elements. in a JAR file. This allows a consumer to be sure that these elements were produced by a specific organization or individual.

Manifest Files

A developer must provide-a manifest lac to indicate which of the components in a JAR file are Java Beans. An example of a manifest file is provided in the following. Listing. It .defines a JAR file that contains four .gift files and one .class file. The last entry is a Bean.

A manifest file may reference several.class files. If a .class file is a Java Bean, its entry must be immediately followed by the line “Java-Bean: True”.

Tabulating the Contents of a JAR File
The following command. lists the contents of Xyz.jar

jar tf Xyz. jar

Extracting Files from a JAR File

The following command extracts the contents of Xyz.jar and places those files in the
current directory:

Ijar xf Xyz.jar

Updating an Existing JAR File
The follo~ing command adds the file filet.class to Xyz.jar:
Ijar -u~ xyz:ja~ file1.class
. .
Recursing Directories
The following command adds all files below directoryX to Xyz.jar:
Ijar _ufo xyz , jar -C directoryX

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Posted on September 18, 2014 in Java Beans

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