Jars a set of files.
The basedir attribute is the reference directory from where to jar.
Note that file permissions will not be stored in the resulting jarfile.
It is possible to refine the set of files that are being jarred. This can be done with the includes, includesfile, excludes, excludesfile and defaultexcludes attributes. With the includes or includesfile attribute you specify the files you want to have included by using patterns. The exclude or excludesfile attribute is used to specify the files you want to have excluded. This is also done with patterns. And finally with the defaultexcludes attribute, you can specify whether you want to use default exclusions or not. See the section on directory based tasks, on how the inclusion/exclusion of files works, and how to write patterns.
This task forms an implicit FileSet and supports all attributes of <fileset> (dir becomes basedir) as well as the nested <include>, <exclude> and <patternset> elements.
You can also use nested file sets for more flexibility, and specify multiple ones to merge together different trees of files into one JAR. The extended fileset and groupfileset attributes from the zip task are also available in the jar task. See the Zip task for more details and examples.
If the manifest is omitted, a simple one will be supplied by Ant.
The update parameter controls what happens if the JAR file already exists. When set to yes, the JAR file is updated with the files specified. When set to no (the default) the JAR file is overwritten. An example use of this is provided in the Zip task documentation. Please note that ZIP files store file modification times with a granularity of two seconds. If a file is less than two seconds newer than the entry in the archive, Ant will not consider it newer.
(The Jar task is a shortcut for specifying the manifest file of a JAR file. The same thing can be accomplished by using the fullpath attribute of a zipfileset in a Zip task. The one difference is that if the manifest attribute is not specified, the Jar task will include an empty one for you.)
Manifests are processed by the Jar task according to the Jar file specification. Note in particular that this may result in manifest lines greater than 72 bytes being wrapped and continued on the next line.