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Is there a quick way to delete a file from a Jar / war without having to extract the jar and recreate it?

Posted by: admin November 30, 2017 Leave a comment

Questions:

So I need to remove a file from a jar / war file.
I was hoping there was something like “jar -d myjar.jar file_I_donot_need.txt”

But right now the only way I can see of doing this from my Linux command line (without using WinRAR/Winzip or linux equivalent) is to

  • Do “jar -xvf” and extract the
    complete Jar file
  • Remove the file(s) I don’t need
  • Rejar the jar file using “jar -cvf”

Please tell me there is a shorter way?

Answers:
zip -d file.jar unwanted_file.txt

jar is just a zip file after all. Definitely much faster than uncompressing/recompressing.

Questions:
Answers:

In Java you can copy all the entries of a jar except the one you want to delete. i.e. you have to make a copy but don’t need to create the individual files.

You can do this by

  • creating a new jar.
  • iterating though the Jar you have
  • copy the entry from one jar to the other, skipping any files you want.
  • close and replace the orginal jar if you want.
Questions:
Answers:

In case you want to delete file in order to unsign signed jar, you can probably just make the .RSA file zero-sized. This can be accomplished with just jar u. See https://stackoverflow.com/a/24678645/653539 . (Worked for me, though I admit it’s hack.)