How to view jar files

[Geoff Garcia]

Aright, I'm pretty much a java newbie.
I understand the basics of the language but have never done real work in it.
Currently I find myself on a project where I'm going to have to do some java development.
I'm at a stage now where I'd like to know whats in all of the jar files utilized by a 3rd party software company that I am interfacing a portal gadget into.
there are a ton of jar files, I've isolated the one I want to view the contents of, but how do I open the darn thing? I've tried wordpad which obviously doesn't work.
Is there some commands I need to run to seperate the .jar file and then be able to view the contents?
Thanks for any help on this simple/novice problem.
Geoff

[Lasse Koskela]

The JDK contains a utility called "jar". You can create, update, extract, and view .jar files using the "jar" utility.
Here are some useful commands:

// Displays the file's contents
jar -tf 3rdparty.jar
// Creates a new .jar file called "myapp.jar" containing
// everything under "com", everything under "fu/bar"
// (but not "fu/rab", for example), and readme.txt
jar -cf myapp.jar com fu/bar readme.txt
// Extracts the file's contents into the current directory
jar -xf 3rdparty.jar
// Updates the .jar file by adding 
// "com/mystuff/Foo.class" into the archive
jar -uf myapp.jar com/mystuff/Foo.class

Hope I didn't post too many typos

[damien malone]

you can open up, add and remove files from jar files by using winzip if you want, might be of some help to you

[Ashik Uzzaman]

I strongly recommend WinRar which is very useful for exploring several kinds of compressed files including ZIP, WAR, TAR etc. I am sure you'ld delighted to get it.

[Lasse Koskela]

Geoff, if you decide to use WinZip/WinRAR/whatever tools for handling your .jar/.war/.ear files, do remember that a valid .jar file must contain the META-INF/MANIFEST.MF file, which is added by default by the jar utility. With WinZip and others, you must create and add the manifest file yourself (it's not difficult, though).

[Arvind Varma]

The commands lasse gave are right..but u can add option 'v' to get a verbose version ..

// Gives the table of contents in verbose fashion
jar -tvf
similarly,
//Extracts the files by displaying the information of every file that is being extracted.
jar -xvf

[Geoff Garcia]

well thanks for the help! I just used the simple winzip tool and got a peek at all the class files in the jars...
I dont know what I was thinking though, looking at .class files is useless to me! I'm trying to figure out why a .jsp call I'm making is failing and thought that by looking at the code of the method I might get a better handle on things.
Any suggestions?
Is there a way to view a .java file from a .class file?

[Vinod John]

Originally posted by Geoff Garcia:

Is there a way to view a .java file from a .class file?

You can actually unjar/unzip the jar file and use a decompiler like JAD to decompile the class file.
http://www.geocities.com/zz_xu/jad.html