Jenkins Global Shared Library Example

Jenkins Global Shared libraries over a powerful way of centralising the functionality that will typically be duplicated across many Jenkinsfile pipelines across your application repositories.

General Structure

• There are component files that represent collections of functionality that are similar, for example maven commands

• There are pipeline files that represent a specific type of pipeline, for example the JavaPipeline file.

• There is an overall Pipelines file. This is the interface that downstream users will interact with. This prevents any internal changes to the files themselves from breaking everyones builds.

Example

There is a Jenkinsfile at the root of this repository that pulls in the libraries and shows how they might be used.

Shared Libraries have some QUIRKS!

Yep, it's Groovy and it's Jenkins so you've got to bare a few things in mind.

No classes

You can't use classes if you want to access Jenkins pipeline methods like sh. Instead, you need to do a little groovy trick.

package com.example.jenkins

def doSomethingCool() {
    sh "./run-my-script.sh"
}

return this

This will give you access to the delegate and owner fields, which contains sh, echo and all the other DSL functions that Jenkins will populate a Jenkinsfile with.

No Fields!

As a consequence of the first quirk, you can't do something like...

package com.example.jenkins

def MY_CONSTANT_VALUE = 'hello'

def doSomething() {
    // Nope, it won't compile.
    echo "${MY_CONSTANT_VALUE}"
}

return this

So instead, you need to wrap the values as functions...

def myConstantValue() { 'hello' }

NO STATIC!

If it's static, it doesn't have the same owner, delegate and this value as the code that has been invoked by the Jenkins server directly. That means if you want to run sh, it needs to be an instance method. This is a quirk of Groovy closures, which you can read more about here.