Selectively include dependencies in JAR

Question

I have a library that I wrote in Scala that uses Bouncy Castle and has a whole bunch of dependencies. When I roll a jar, I can either roll a "fat" jar that has all the dependencies (including scala), which weighs in around 19 MB, or I can roll a skinny jar, which doesn't have dependencies, but is only a few hundred KB.

The problem is that I need to include the Bouncy Castle classes/jar with my library, because if its not on the classpath at runtime, all kinds of exceptions get thrown.

So, I think the ideal situation is if there is some way that I can get either Maven or SBT to include some but not all dependencies in the jar that gets rolled. Some dependencies are needed at compile-time, but not at run time, such as the Scala standard libraries. Is there some way to get that to happen?

Thanks!

Answer 1

I would try out the sbt proguard plugin from https://github.com/nuttycom/sbt-proguard-plugin . It should be able to weed out the classes that are not in use.

Answer 2

If it is sufficient to explicitly define which dependencies should be added (one the artifact-level, i.e., single JARs), you can define an assembly (in case of a single project) or an additional assembly project (in case of a multi-module project). Assembly descriptors can explicitly exclude/include artifacts from the dependencies.

Here is some good documentation on this topic (section 8.5.4), here is the official documentation.

Note that you can include all artifacts that belong to one group by using the wildcard notation in dependecySets, e.g. hibernate:*:jar would include all JAR files belonging to the hibernate group.