sbt-assembly: how to link dependencies jar with main jar?

Question

I am coding in scala and using SBT with sbt-assembly plugin. My project has a lot of external libraries, and therefore sbt-assembly takes a long time to pack the JAR file. I would like to have a separate jar files for my code and for the dependencies. Therefore, I could simply recompile and repack only my code. How to do this?

Progress so far:

The following commands in the build.sbt prevents sbt-assembly from packing the libraries:

assembleArtifact in packageScala := false

assembleArtifact in packageDependency := false

Then separate jars can be built by passing following commands: assembly, assembly-package-scala and assembly-package-dependency. They make three jars: one containing my program, one with scala libraries and one with all the dependencies.

However, the jar file is not executable anymore because it does not see the dependencies in the separate jar file. I think I need to add a classpath to assembly-sbt, but I am not sure how to do this.

Answer 1

Use sbt-pack plugin at https://github.com/xerial/sbt-pack . So far I've found it the cleanest way to pack the project and dependencies.

Answer 2

See Setting Classpath Still Can't Find External Jar. Oracle says:

When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.

So, you have to say:

java -cp "foo-assembly-0.1-deps.jar:foo-assembly-0.1.jar" Main

where Main is the name of the main class, and : is the file separator on your OS (; on Windows) .

Currently there seems to be a bug in assembly-package-scala and it comes out empty, but it shouldn't matter because assembly-package-dependency contains Scala library too.