How do I import a Groovy class into a Jenkinfile?

Question

How do I import a Groovy class within a Jenkinsfile? I've tried several approaches but none have worked.

This is the class I want to import:

Thing.groovy

class Thing {
    void doStuff() { ... }
}

These are things that don't work:

Jenkinsfile-1

node {
    load "./Thing.groovy"

    def thing = new Thing()
}

Jenkinsfile-2

import Thing

node {
    def thing = new Thing()
}

Jenkinsfile-3

node {
    evaluate(new File("./Thing.groovy"))

    def thing = new Thing()
}

Answer 1

You can return a new instance of the class via the load command and use the object to call "doStuff"

So, you would have this in "Thing.groovy"

class Thing {
   def doStuff() { return "HI" }
}

return new Thing();

And you would have this in your dsl script:

node {
   def thing = load 'Thing.groovy'
   echo thing.doStuff()
}

Which should print "HI" to the console output.

Would this satisfy your requirements?