How can I fix missing conf files when using shadowJar and Scala dependencies?

Question

Writing this for users who have future issues like me. Libraries that are built on the Typesafe config typically use their own reference.conf files and refer to certain configuration keys. When building a fat JAR using the Gradle shadowJAR plugin, these files aren't included.

Dependencies like Spray and Akka throw errors when the fat JAR attempts to run. Errors look like:

Exception in thread "main" com.typesafe.config.ConfigException$Missing: No configuration setting found for key 'spray'
Exception in thread "main" com.typesafe.config.ConfigException$Missing: No configuration setting found for key 'akka'

How to fix this? Check the answer below.

Answer 1

Simply:

  shadowJar {
    append('reference.conf')
  }

See Controlling JAR Content Merging

Answer 2

The resulting fix was to add the following to the build.gradle file:

shadowJar {
  transform(com.github.jengelman.gradle.plugins.shadow.transformers.AppendingTransformer) {
    resource = 'reference.conf'
  }
}

Solution was found here:http://www.sureshpw.com/2015/10/building-akka-bundle-with-all.html