JAR Files

cousin_borat

Is it possible to update a .class file in a JAR archive?

using jar uf XXX.jar file.class

or do you always need to rebuild the complete jar file?

pretty sure you can't but wanted to make really sure

TabulaRasa

Just unzip the jar file using Winzip/7Zip or whatever. You will notice that there are directories created for each of the packages. Now just replace the class in the directory you wish.

cgarvey

Checkout the help of jar

jar --help

and specifically the -u flag.

# edit text.txt

jar -cf my.jar text.txt

# edit text.txt

jar -uf my.jar text.txt

Should do what you're after

cousin_borat

cgarvey wrote:

Checkout the help of jar

jar --help

and specifically the -u flag.

I had tried that but it won't replace a file that is already in the jar. As far as I can see -u only will update the jar with a new file. I ended up unpacking the jar contents, adding the .class file to the directory and repacking into a jar again.

Hobbes

Jar files are basically zip files. You can just unzip it and replace it. The only issue would be if the jar or class file is signed in which case you would need to update the manifest file.

marco_polo

cousin_borat wrote:

I had tried that but it won't replace a file that is already in the jar. As far as I can see -u only will update the jar with a new file. I ended up unpacking the jar contents, adding the .class file to the directory and repacking into a jar again.

jar -uf test.jar test.class is definately right regardless of whether or not the file exists already it should be saved to the jarfile.

I use this comand all the time in build scripts at work to edit Manifest files etc.

cgarvey

cousin_borat wrote:

I had tried that but it won't replace a file that is already in the jar.

In my example above, it works. So maybe it only works on text files, but that example works for me (JDK1.5)

cousin_borat

Hi there,

the jar files had a manifest file that needed to be updated as well. Once this was done the new class file was added to the jar fine.

Thanks for your help!