How to inject MANIFEST.MF into jar

Question

I was trying to, for debugging purposes, inject a (hacked) META-INF/MANIFEST.MF file into a jar. I created a META-INF dir at the same level where the jar is and created my MANIFEST.MF file in it. Then, per this tutorial:

jar uf myjar-with-dependencies.jar META-INF/MANIFEST.MF

which executed without error but just wiped out the existing manifest without replacing it. I know it because I ran:

jar tf myjar-with-dependencies.jar | grep MANIFEST

which, before the update, returned the found file in the jar but does not now after the update.

Answer 1

"jar ufm" is what you're after. The m argument specifies that you're providing a manifest file.

jar ufm <yourJar> <yourManifest>

Otherwise it just treats it as a regular file which will end up getting stomped on when it generates the default manifest file.

Answer 2

A Jar is just a zip file. You can open it up using any tool you would normally use to open a zip file and then just place your file inside of it where you want.