Jenkins Pipeline Shared Libraries: Reusable CI/CD Code Across Teams

The Copy-Paste Problem

After your third Jenkins pipeline, the same 50 lines of Groovy appear everywhere: Docker build steps, Slack notifications, artifact uploads. Shared libraries extract reusable code into a versioned, testable repository.

Repository Structure

jenkins-shared-library/
  vars/           # Callable functions: dockerBuild.groovy, notifySlack.groovy
  src/            # Groovy classes: com/myorg/DockerUtils.groovy
  resources/      # Templates and config files

Configure in Jenkins: Manage Jenkins → Configure System → Global Pipeline Libraries.

Global Variables (vars/)

vars/dockerBuild.groovy:

def call(Map config = [:]) {
    def imageName = config.imageName ?: env.BUILD_TAG
    pipeline {
        agent any
        stages {
            stage('Build') {
                steps { script { docker.build(imageName, '.') } }
            }
        }
    }
}

Usage: @Library('myorg-lib') _ then dockerBuild(imageName: "myregistry.com/app:${BUILD_NUMBER}").

Shared Classes (src/)

src/com/myorg/DockerUtils.groovy:

package com.myorg
class DockerUtils implements Serializable {
    def steps
    DockerUtils(steps) { this.steps = steps }
    def buildAndPush(String name, String registry) {
        steps.sh "docker build -t ${registry}/${name} ."
        steps.sh "docker push ${registry}/${name}"
    }
}

Usage: def docker = new com.myorg.DockerUtils(steps); docker.buildAndPush('app', 'registry.example.com').

Versioning

Tag releases: git tag v1.0.0 && git push --tags. Reference in pipelines: @Library('myorg-lib@v1.0.0') _.

Migration Strategy

Find code repeated 3+ times across Jenkinsfiles, extract to vars/, test in one pipeline, roll out. For complex logic with 3+ methods, use src/ classes. Version with git tags for production pipelines.