What: Strange problem when starting up Wildfly from within Maven with Wildfly Maven plugin and goal wildfly:start/wildfly:run
Why: Good to know
How: Remove corrupt file

Wildfly Maven plugin is great: Download and run a wildfly from scratch (with such goodies like installing database drivers during build, adding test users, setting ports, …) and deploy your application to it. I like it very much (until yesterday ;-)).

From one day to another the plugin stopped working. The error message was something about API incompatibility and Null Pointer exception in class org.wildfly.plugin.server.RuntimeVersion (line 46) when executing goal wildfly:start/wildfly:run. Deploy goal worked well.

After digging in the source code and going from org.wildfly.plugin.server.RuntimeVersion:init ⇒ org.jboss.jdf.stacks.clientStacksClient:getStacks ⇒ org.jboss.jdf.stacks.clientStacksClient:initializeStacks the reason of the problem was obvious: It reads a file downloaded from the web and stored in the temp-folder: …/AppData/Local/Temp/httpsrawgithubcomjbossjdfjdfstack100Finalstacksyamlstacks.yaml. If the file is there, it is not downloaded and the existing version is used. In my case, the file was corrupt (0 B). Deleting the file, executing the wildfly:run goal and everything was working again.

And they all lived happily ever after.