SBT project for java executable jar

Question

What is the best way to set the target package for an SBT project to be an executable jar file?

It would need to bundle scala-library.jar and set the manifest for main-method.

Solution

Use the assembly-sbt plugin (originally created by Coda Hale, now maintained by Eugene Yokota): https://github.com/sbt/sbt-assembly

Once you add this to your project it will build a so-called "fatjar" which is executable via java -jar projectName-assembly.jar. It will autodetect your main method -- if there is more than one in your source, you can explicitly set which one to use by setting mainclass, e.g.:

mainClass in assembly := Some("com.package.ClassNameWithMain")

Note: I edited this answer to be up-to-date with the current release of SBT (0.11+).

Comments

[huynhjl]

Have a look at github.com/retronym/sbt-onejar. I haven't tried myself but I'm interested to know if that works. Also if that does not work, retronym also points to github.com/nuttycom/sbt-proguard-plugin.

[Synesso]

Thanks huynhjl. It worked fine, but I decided against it as one-jar itself seems full of classloading jiggery-pokery. I prefer the mega-jar approach of assembly-sbt.

[Synesso]

Thanks Thomas. It's a good one. Simple to use. Would benefit from having proguard trim out the fat.

[Philippe]

You can use the Proguard plugin to do that. Make sure you specify that you want to keep the main class.

[Thomas Lockney]

Yes, Proguard can do this, but it's a pain to configure correctly. The beauty of the sbt-assembly is how incredibly simple it is.

[Nishan]

@folone I tried this using assembly and generated jar but still it won't execute using double click. How do I create executable jar which will run when you click on it?