How does DSL extension in Jenkins plugin work

Question

I want to create DSL extension for my Jenkins plugin (built using maven) just like in the example of Docker plugin for Jenkins. I see that the groovy file Docker.groovy is in: src/main/resources/org/jenkinsci/plugins/docker/workflow/Docker.groovy

Does this groovy file have to be within org.jenkinsci.plugin.docker.workflow, or can I just put it inside resources? What is the difference?

Also, If I define my DSL extension within the groovy file in this manner is the DSL extension available to call implicitly in the pipeline file?

Answer 1

In order to make a step available in the Pipeline DSL through your plugin, you need to define a subclass of Step that performs the needed task. This can be completely done within Java, and is the preferred method for adding expanding the Pipeline DSL within a Jenkins plugin.

The Docker example you linked is unusual in this instance, and doesn't define a typical Pipeline DSL step (the docker directive in Pipeline functions like a cross between an agent, a step and a context block). Furthermore, it appears to include a Java class that loads the Groovy script dynamically, which acts as the entry point into the directive.

Groovy can be used to expand the Pipeline DSL; however this is done within the context of a shared library, which is meant to be more of a boilerplate reducing tool to be used internally.