Java Reference
In-Depth Information
-x
Extract files from a JAR file.
-t
List files in a JAR.
-f
Specify the JAR filename.
-v
Be verbose—display descriptions of what the
jar
utility is doing as it
does it.
-m
Add the contents of the named file to the manifest.
5.12
T
HE
R
EST OF THE
T
OOLKIT
There are additional utilities in the toolkit. Below is a capsule summary of them
and their purposes.
extcheck
This utility checks an applet JAR file for any extensions it requires that are
in conflict with the current Java runtime environment. (But we don't
cover applets in this topic.)
jarsigner
This is a utility for digitally signing JAR file. Once a JAR is signed, anyone
looking at it can be sure of two things—first, the file was definitely pre-
pared by the owner of the private key that matches the public key used to
verify the signature;
29
and second, the JAR file has not been modified in
any way since it was signed. In other words, depending upon the care with
which the signer treats his/her private key, this certifies the authenticity
29. A discussion of public/private keys as an authentication mechanism is beyond our scope
here. As a shameless plug, Mr. Schwarz would like to point you to Chapter 10 of his previous
topic,
Multitool Linux
, which contains a beginner's introduction to public key authentication
using GnuPG. Of course, a quick Google search will find you many online descriptions that
are free.
