jar-The Java Archive Tool










Documentation Contents



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jar-The Java Archive Tool

jar combines multiple files into a single JAR archive file.


Synopsis

Description

Options

Command Line Argument Files

Examples

See Also


SYNOPSIS



Create jar file

jar c[v0M]f jarfile
[-C dir]
inputfiles
[-Joption]

jar c[v0]mf manifest
jarfile [-C dir]
inputfiles
[-Joption]
[-e entrypoint]

jar c[v0M] [-C
dir] inputfiles
[-Joption]

jar c[v0]m manifest
[-C dir]
inputfiles
[-Joption]

Update jar file

jar u[v0M]f jarfile
[-C dir]
inputfiles
[-Joption]

jar u[v0]mf manifest
jarfile [-C dir]
inputfiles
[-Joption]
[-e entrypoint]

jar u[v0M] [-C
dir] inputfiles
[-Joption]

jar u[v0]m manifest
[-C dir]
inputfiles
[-Joption]

Extract jar file

jar x[v]f jarfile
[inputfiles]
[-Joption]

jar x[v] [inputfiles]
[-Joption]

List table of contents of jar file

jar t[v]f jarfile
[inputfiles]
[-Joption]

jar t[v] [inputfiles]
[-Joption]

Add index to jar file

jar i jarfile
[-Joption]


where:



cuxtiv0Mmf

Options that control the jar command.


jarfile

File name of the Jar file to be created (c), updated
(u), extracted (x), or have its
table of contents viewed (t). The
-f option and filename jarfile are a
pair -- if either is present, they must both appear. Note
that omitting -f and jarfile accepts
jar file from standard input (for x and t) or sends
jar file to standard output (for c and u).


inputfiles

Files or directories separated by spaces, to be
combined into jarfile (for c and u), or to be
extracted (for x) or listed (for t) from jarfile.
All directories are processed recursively. The files are
compressed unless option -0 (zero) is
used.


manifest

Pre-existing manifest file whose
name : value pairs are to be
included in MANIFEST.MF in the jar file. The -m
option and filename manifest are a pair -- if
either is present, they must both appear. The letters
m and f must appear in the same order that
manifest and jarfile appear.



entrypoint
The name of the class that set as the application entry
point for stand-alone applications bundled into
executable jar file. The -e option and entrypoint
are a pair -- if either is present, they must both appear.
The letters m, f and e must appear in
the same order that manifest, jarfile,
entrypoint appear.






-C dir

Temporarily changes directories to dir while
processing the following inputfiles argument.
Multiple -C dir
inputfiles sets are allowed.

-J option

Option passed into the Java runtime environment.
(There must be no space between -J and
option).




DESCRIPTION


The jar tool combines multiple files into a single JAR
archive file. jar is a general-purpose archiving and
compression tool, based on ZIP and the ZLIB compression format.
However, jar was designed mainly to facilitate the
packaging of java applets or applications into a single
archive. When the components of an applet or application
(.class files, images and sounds) are combined into a single
archive, they may be downloaded by a java agent (like a
browser) in a single HTTP transaction, rather than requiring a
new connection for each piece. This dramatically improves
download times. jar also compresses files and so further
improves download time. In addition, it allows individual
entries in a file to be signed by the applet author so that
their origin can be authenticated. The syntax for the jar tool
is almost identical to the syntax for the tar command.
A jar archive can be used as a class path entry, whether or not it is compressed.

Typical usage to combine files into a jar file is:



C:\Java> jar cf myFile.jar *.class

In this example, all the class files in the
current directory are placed into the file named "myFile.jar".
A manifest file entry named META-INF/MANIFEST.MF is
automatically generated by the jar tool and is always the first
entry in the jar file. The manifest file is the place where any
meta-information about the archive is stored as
name : value pairs. Refer to the
JAR file
specification for details about how meta-information is
stored in the manifest file.

If you have a pre-existing manifest file whose
name: value pairs you want the
jar tool to include for the new jar archive, you can specify it
using the -m option:



C:\Java> jar cmf myManifestFile myFile.jar *.class

An existing manifest file must end with a
new line character.  jar does not parse the last line of a manifest file if it does not end with a new line character.

Note:  A jar command that specifies cfm on the command line instead of cmf (the
order of the -m and -f options are reversed), the jar command line must specify the name of the
jar archive first, followed by the name of the manifest file:



C:\Java> jar cfm myFile.jar myManifestFile *.class



The manifest is in a text format inspired by
RFC822 ASCII format, so it is easy to view and process
manifest-file contents.

To extract the files from a jar file, use -x, as
in:



C:\Java> jar xf myFile.jar



To extract only certain files from a jar file, supply their
filenames:



C:\Java> jar xf myFile.jar foo bar



Beginning with Java 2 SDK v1.3, the
jar utility supports JarIndex, which
allows application class loaders to load classes more
efficiently from jar files. If an application or applet is
bundled into multiple jar files,  only the necessary jar
files will be downloaded and opened to load classes. This
performance optimization is enabled by running jar
with the -i option. It will generate package location
information for the specified main jar file and all the jar
files it depends on, which need to be specified in the
Class-Path attribute of the main jar file's
manifest.



C:\Java> jar i main.jar



In this example, an INDEX.LIST file is inserted into the
META-INF directory of main.jar.
The application class loader will use the information stored in
this file for efficient class loading.  Refer to the
JarIndex specification for details about how location
information is stored in the index file.

A standard way to copy directories is to first compress
files in dir1 to standard out, then extract from standard in to
dir2 (omitting f from both jar
commands):



C:\Java> (cd dir1; jar c .) | (cd dir2; jar x)



Examples of using the jar tool to operate on jar files and
jar file manifests are provided below
and in the Jar trail of the Java
Tutorial.


OPTIONS





c

Creates a new archive file named jarfile (if f is
specified) or to standard output (if f and
jarfile are omitted). Add to it the files and
directories specified by inputfiles.



u


Updates an existing file jarfile (when f is
specified) by adding to it files and directories specified
by inputfiles. For
example:



jar uf foo.jar foo.class

adds the file foo.class to the
existing jar file foo.jar. The -u
option can also update the manifest entry, as given by this
example:



jar umf manifest foo.jar

updates the foo.jar manifest with the
name: value pairs in
manifest.




x

Extracts files and directories from jarfile (if f is
specified) or standard input (if f and
jarfile are omitted). If inputfiles is specified, only
those specified files and directories are extracted.
Otherwise, all files and directories are extracted.
The time and date of the extracted files are those
given in the archive.



t

Lists the table of contents from jarfile (if f is
specified) or standard input (if f and
jarfile are omitted). If inputfiles is specified, only
those specified files and directories are listed. Otherwise,
all files and directories are listed.



i


Generate index information for the specified jarfile and its dependent jar
files. For example:



jar i foo.jar



generates an INDEX.LIST file in
foo.jar which contains location information for
each package in foo.jarClass-Path attribute of
foo.jar. See the index example.



f

Specifies the file jarfile to be created
(c), updated (u), extracted
(x), indexed (i), or viewed
(t). The -f option and filename
jarfile are a pair -- if present, they must both
appear. Omitting f and jarfile accepts
a "jar file" from standard input (for x and t) or sends the
"jar file" to standard output (for c and u).



v

Generates verbose output to standard output. Examples shown below.



0

(zero) Store without using ZIP compression.



M

Do not create a manifest file entry (for c and u), or
delete a manifest file entry if one exists (for u).



m


Includes name: value
attribute pairs from the specified manifest file
manifest in the file at
META-INF/MANIFEST.MF. A
name: value pair is added
unless one already exists with the same name, in which case
its value is updated.

On the command line, the letters m and f
must appear in the same order that manifest and
jarfile appear. Example use:



jar cmf myManifestFile myFile.jar *.class

You can add special-purpose name : value attribute pairs to the manifest that aren't contained in the default manifest. For example, you can add attributes specifying vendor information, version information, package sealing, or to make JAR-bundled applications executable. See the
JAR
Files trail in the Java Tutorial for examples of using the
-m option.




e


Sets entrypoint as the application entry
point for stand-alone applications bundled into executable jar file.
The use of this option creates or overrides the Main-Class attribute
value in the manifest file.

This option can be used during creation of jar
file or while updating the jar file.


This option specifies the application entry point without editing or
creating the manifest file.


For example, this command creates Main.jar where the Main-Class attribute value in the manifest is set to Main:


jar cfe Main.jar Main Main.class



The java runtime can directly invoke this application by running the following command:



java -jar Main.jar


If the entrypoint class name is in a package it may use either a dot (".")
or slash ("/") character as the delimiter.
For example, if Main.class is in a package called
foo the entry point can be specified in the following ways:

jar -cfe Main.jar foo/Main foo/Main.class

or

jar -cfe Main.jar foo.Main foo/Main.class


Note:  specifying both -m and -e options together when the given
manifest also contains the Main-Class attribute results in an ambigous
Main.class specification, leading to an error and the jar creation or
update operation is aborted.






-C  dir


Temporarily changes directories
(cd dir) during execution of the
jar command while processing the following
inputfiles argument. Its operation is intended to
be similar to the -C option of the UNIX
tar utility. For example:



jar uf foo.jar -C classes bar.class

changes to the classes directory
and add the bar.class from that directory to
foo.jar. The following command,



jar uf foo.jar -C classes . -C bin xyz.class

changes to the classes directory
and adds to foo.jar all files within the
classes directory (without creating a classes
directory in the jar file), then changes back to the
original directory before changing to the bin
directory to add xyz.class to foo.jar. If
classes holds files bar1 and
bar2, then here's what the jar file
contains using jar tf foo.jar:



META-INF/
META-INF/MANIFEST.MF
bar1
bar2
xyz.class






-Joption

Pass option to the Java runtime environment, where
option is one of the options described on the
reference page for the java
application launcher. For example,
-J-Xmx48M sets the maximum memory to 48
megabytes. It is a common convention for -J to pass options
to the underlying runtime environment.



COMMAND LINE ARGUMENT FILES


To shorten or simplify the jar command line, you can specify
one or more files that themselves contain arguments to the
jar command (except -J options). This
enables you to create jar commands of any length, overcoming
command line limits imposed by the operating system.

An argument file can include options and filenames.
The arguments within a file can be space–separated or newline-separated.
Filenames within an argument file are relative to the current
directory, not relative to the location of the argument file. Wildcards (*)
that might otherwise be expanded by the operating system shell
are not expanded. Use of the @ character to recursively
interpret files is not supported. The -J options are
not supported because they are passed to the launcher, which
does not support argument files.

When executing jar, pass in the path and name of each
argument file with the @ leading character. When jar
encounters an argument beginning with the character
@, it expands the contents of that file into the
argument list.

For example, you can use a single argument file named
classes.list to hold the names of the files:



C:\Java> dir /b *.class > classes.list



Then execute the jar command passing in the argfile:



C:\Java> jar cf my.jar @classes.list

An argument file can be passed in with a path, but
any filenames inside the argument file that have relative paths
are relative to the current working directory, not the path
passed in. Here's such an example:



C:\Java> jar @path1/classes.list






EXAMPLES


To add all the files in a particular directory to an archive
(overwriting contents if the archive already exists).
Enumerating verbosely (with the v option) will tell you more
information about the files in the archive, such as their size
and last modified date.



C:\Java> dir
12/09/96 12:20a <DIR> .
12/09/96 12:17a <DIR> ..
12/09/96 12:18a 946 1.au
12/09/96 12:18a 1,039 2.au
12/09/96 12:18a 993 3.au
12/09/96 12:19a 48,072 spacemusic.au
12/09/96 12:19a 527 at_work.gif
12/09/96 12:19a 12,818 monkey.jpg
12/09/96 12:19a 16,242 Animator.class
12/09/96 12:20a 3,368 Wave.class
10 File(s) 91,118 bytes

C:\Java> jar cvf bundle.jar *
adding manifest
adding: 1.au
adding: 2.au
adding: 3.au
adding: Animator.class
adding: Wave.class
adding: at_work.gif
adding: monkey.jpg
adding: spacemusic.au

If you already have separate subdirectories for images, audio
files and classes, you can combine them into a single jar file:

C:\Java> dir
12/09/96 12:11a <DIR> .
12/09/96 12:17a <DIR> ..
12/03/96 06:54p <DIR> audio
12/06/96 02:02p <DIR> images
12/09/96 12:10a <DIR> classes
5 File(s) 207,360 bytes

C:\Java> jar cvf bundle.jar audio classes images
adding: audio/1.au
adding: audio/2.au
adding: audio/3.au
adding: audio/spacemusic.au
adding: classes/Animator.class
adding: classes/Wave.class
adding: images/monkey.jpg
adding: images/at_work.gif

C:\Java> dir
12/09/96 12:11a <DIR> .
12/09/96 12:17a <DIR> ..
12/09/96 12:11a 207,360 bundle.jar
12/03/96 06:54p <DIR> audio
12/06/96 02:02p <DIR> images
12/09/96 12:10a <DIR> classes
6 File(s) 207,360 bytes

To see the entry names in the jarfile, use the "t"
option:



C:\Java> jar tf bundle.jar
META-INF/
META-INF/MANIFEST.MF
audio/1.au
audio/2.au
audio/3.au
audio/spacemusic.au
classes/Animator.class
classes/Wave.class
images/monkey.jpg
images/at_work.gif



To add an index file to the jar file
for speeding up class loading, use the -i option.


Let's say you split the inter-dependent classes for a stock
trade application, into three jar files:  main.jar,
buy.jar, and sell.jar. If you specify the
Class-path attribute in the main.jar manifest as:

Class-Path: buy.jar sell.jar

then you can use the -i option to speed up your
application's class loading time:

C:\Java> jar i main.jar


An INDEX.LIST file is inserted to the META-INF directory
which will enable the application class loader to download the
specified jar files when it is searching for classes or resources.



SEE ALSO


The Jar
Overview
The Jar File
Specification
The JarIndex
Spec
Jar
Tutorial on the Java Software web site.
pack200 Reference Page






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