How could I repack a jar file with all of its dependencies?

Question

I am developing an application which is supposed to run standalone. However, this project involves a .jar file which contains a lot of dependencies, and if I simply distribute this .jar file with the application, it won't work.

I wonder if there is any way in which I could unpack the file, add the dependencies and repack it again? I hope there are some automatic mechanism for this, since the manual process could take hours, and there might be other referenced jar files.

P.S. I am using Eclipse, but since I am going to deploy this project with Web Start, exporting the project with the build-in export tool might not be a good idea since my attempts all ended up with ClassNotFoundException, so I suspect I might have to pack the project into several jars.

Thanks!

Answer 1

Repacking an unpacked JAR is a little frustrating because of the folder structure

When unpacking with:

jar xvf JAR_NAME.jar

you get a JAR_NAME/ folder

To repack the JAR:

• remove old jar

  rm JAR_NAME.jar

• get inside the folder

  cd JAR_NAME

• pack the jar referencing the parent folder

  jar cf ../JAR_NAME.jar *

and you will end up with the JAR_NAME.jar in the parent folder, where the original was unpacked from, without the first folder level you would get if you had packed the folder itself.

Answer 2

For Spring Boot 2.1.9.RELEASE I managed to unpack and re-pack the fat jar like this: Move into the folder with the jar file.

Extract jar file

jar xvf app.jar

Remove old jar file

rm app.jar

Create new jar file in parent dir

jar cmf0 META-INF/MANIFEST.MF ../app.jar  *

m ... use a specific manifest-file

0 ... deactivates compression, which circumvents that the dependencies(jar-files) are compressed

Documentation can also be found here: https://docs.oracle.com/javase/tutorial/deployment/jar/build.html