How to Deploy Xtext to a Headless Plain-Java Environment?

Yesterday, Sven and I were at the Eclipse Democamp in Hannover which was organized by brox IT-Solutions and Bredex - thanks for the nice event. I met interesting people and we discussed various topics. One particular question about Xtext was raised several times from different sides: How do I use my language in an environment without Eclipse, e.g. on a build server? As this was already possible from the first minute even with the former oAW version of Xtext and with Xtext 0.7.0, too, I was kind of suprised. In fact, any execution of the generator workflow uses Xtext in a standalone environment - without OSGi, Equinox or any dependency on Eclipse UI. The problem seems to be another one: How can I determine all the required libraries to deploy my Xtext-driven generator?

It turns out that this task is suprisingly easy with Eclipse. We'll use a minor trick to simplify the necessary steps. First of all, we have to create a new Run Configuration for a Java Application. Actually this one will never be executed, but we need to refer to this one in the next step. Just create a new configuration for your generator-project and use the org.eclipse.emf.mwe2.launch.runtime.Mwe2Launcher as the main class:

Now that we have a run configuration for the generator project, let's export the project as a runnable jar. Choose Export... -> Runnable JAR file from the context menu of the generator project. The wizard will ask for a launch configuration and that's where we use the one that we created a second ago:

Select the options of your choice, point to a target file and hit the Finish-button. Eclipse will collect required libraries and add the necessary entries to the MANIFEST.MF in the runnable JAR file. As I already said, it's suprisingly simple.

Last but not least, I recommend to create a batch file or shell script that starts a virtual machine, points to the exported archive and refers to the module name of the generator workflow, e.g.:
java -jar exported.jar workflow.MyDslGenerator
It's probably a good idea to wrap the invocation of the Mwe2Launcher in a custom main class to encapsulate the name of the generator workflow and pass additional arguments to the workflow.