Extracting the Contents of a JAR File

The basic command to use for extracting the contents of a JAR file is:

Let’s look at the options and arguments in this command:

• The x option indicates that you want to extract files from the JAR archive.
• The f options indicates that the JAR file from which files are to be extracted is specified on the command line, rather than through stdin.
• The jar-file argument is the filename (or path and filename) of the JAR file from which to extract files.
• archived-file(s) is an optional argument consisting of a space-separated list of the files to be extracted from the archive. If this argument is not present, the Jar tool will extract all the files in the archive.

As usual, the order in which the x and f options appear in the command doesn’t matter, but there must not be a space between them.

When extracting files, the Jar tool makes copies of the desired files and writes them to the current directory, reproducing the directory structure that the files have in the archive. The original JAR file remains unchanged.

An Example

Let’s extract some files from the TicTacToe JAR file we’ve been using in previous sections. Recall that the contents of TicTacToe.jar are:

Suppose you want to extract the TicTacToe class file and the cross.gif image file. To do so, you can use this command:

This command does two things:

• It places a copy of TicTacToe.class in the current directory.
• It creates the directory images, if it doesn’t already exist, and places a copy of cross.gif within it.

The original TicTacToe JAR file remains unchanged.

As many files as desired can be extracted from the JAR file in the same way. When the command doesn’t specify which files to extract, the Jar tool extracts all files in the archive. For example, you can extract all the files in the TicTacToe archive by using this command:

Extracting .jar file with command line

I am trying to extract the files from a .jar file. How do I do that using command line?

I am running Windows 7

8 Answers 8

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

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

The folder where jar is probably isn’t C:\Java for you, on my Windows partition it’s:

Unless the location of jar is in your path environment variable, you’ll have to specify the full path/run the program from inside the folder.

EDIT: Here’s another article, specifically focussed on extracting JARs: http://docs.oracle.com/javase/tutorial/deployment/jar/unpack.html

Note that a jar file is a Zip file, and any Zip tool (such as 7-Zip) can look inside the jar.

unzip file.jar -d dir_name_where_extracting

You can use the following command: jar xf rt.jar

Where X stands for extraction and the f would be any options that indicate that the JAR file from which files are to be extracted is specified on the command line, rather than through stdin.

Java has a class specifically for zip files and one even more specifically for Jar Files.

using those you could, on a command from the console, using a scanner set to system.in

then get all the components and write them as a file.

You can also use java.util.zip.ZipInputStream instead, as seeing a JAR file is in the same format as a ZIP file, ZipInputStream will be able to handle the Jar file, in fact JarInputStream actually extends ZipInputStream.

an alternative is also instead of getNextJarEntry, to use getNextEntry

Running JAR file on Windows

I have a JAR file named helloworld.jar. In order to run it, I’m executing the following command in a command-line window:

This works fine, but how do I execute it with double-click instead? Do I need to install any software?

25 Answers 25

Easiest route is probably upgrading or re-installing the Java Runtime Environment (JRE).

• Open the Windows Explorer, from the Tools select ‘Folder Options. ‘
• Click the File Types tab, scroll down and select JAR File type.
• Press the Advanced button.
• In the Edit File Type dialog box, select open in Actions box and click Edit.
• Press the Browse button and navigate to the location the Java interpreter javaw.exe.
• In the Application used to perform action field, needs to display something similar to C:\Program Files\Java\j2re1.4.2_04\bin\javaw.exe» -jar «%1» % (Note: the part starting with ‘javaw’ must be exactly like that; the other part of the path name can vary depending on which version of Java you’re using) then press the OK buttons until all the dialogs are closed.

In Windows Vista or Windows 7, the manual file association editor has been removed.

The easiest way is to run Jarfix, a tiny but powerful freeware tool. Just run it and your Java apps is back. double-clickable again.

If you need to distribute your .jar file and make it runnable at other people’s Windows computers, you can make a simple .bat file like this in the command prompt:

and place the .bat file in the same directory as your .jar file.

If you have a jar file called Example.jar, follow these rules:

1. Open a notepad.exe
2. Write : java -jar Example.jar
3. Save it with the extension .bat
4. Copy it to the directory which has the .jar file
5. Double click it to run your .jar file

An interesting side effect of this causes a problem when starting runnable jar files in the command prompt.

If you try (in a command prompt):

No joy, because this is being translated to the following (which doesn’t work):

However, the following command does work:

If you change the association in file manager as described above to:

Then you can type:

in the command prompt and it will now work!

EDIT:(However you then get a black console window when you run a form based (non console) Java app, so this is not an ideal solution)

If you run these jar files by double clicking them in windows, no parameters will be passed so your Java code needs to handle the stack overflow exception and include a «press a key» function at the end or the window will just disappear.

In order to pass a parameter in windows you have to create a shortcut to the jar file, which includes the parameter in the target line (right click on the shortcut and select properties) you can not add parameters to the jar file icon itself in this way.

There isn’t a single, consistent solution here, but you would have the same problem with any other console application.

There is a windows freeware application called «bat to exe» which you can use to create an exe file from a .bat file with the apropriate command line in it. you can also embed the jar file in the exe with this application, and make it clean it up when it has finished running, so this may be a more elegant solution.

jar-The Java Archive Tool

SYNOPSIS

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

Typical usage to combine files into a jar file is:

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:

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: 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:

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

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.

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):

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

generates an INDEX.LIST file in foo.jar which contains location information for each package in foo.jar and all the jar files specified in the Class-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:

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 :

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

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: or 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: changes to the classes directory and add the bar.class from that directory to foo.jar. The following command, 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 : -J option 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

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:

Then execute the jar command passing in the argfile:

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:

EXAMPLES

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

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

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