Step 10 - Shared Library

To keep our pipeline DRY (Don't Repeat Yourself), we extract the Docker build/push logic into a shared library method dockerBuildPush.

Jenkinsfile

Here is the Jenkinsfile for this step. Source code: 30-10-Jenkinsfile-docker-build-push-to-artifactory-condition-shared-library.

@Library('library') _

pipeline {
    agent any
    options {
      disableConcurrentBuilds()
      disableResume()
      buildDiscarder(logRotator(numToKeepStr: '10'))
      timeout(time: 1, unit: 'HOURS')
    }
    tools {
        maven 'maven-3.6.3'
    }
    parameters {
        choice(name: 'dockerRegistry', choices: ['Dockerhub', 'JfrogArtifactory'], description: 'Select Docker Registry')
    }
    environment {
        DATE = new Date().format('yy.M')
        TAG = "${DATE}.${BUILD_NUMBER}"
    }
    stages {
        stage ('Build') {
            steps {
                sh 'mvn clean package'
            }
        }
        stage('Docker build and push to Docker Registry') {
            steps {
                script {
                    dockerBuildPush("${params.dockerRegistry}")
                }
            }
        }
    }
    post {
      always {
        deleteDir()
      }
    }
}

Detailed Explanation

Shared Library Import

• @Library('library') _: This single line at the top loads the Shared Library configured in Jenkins Global Configuration as "library". The underscore _ imports everything so you can use global variables (steps) directly.

Custom Step

• dockerBuildPush(...): This is NOT a standard Jenkins step. It is a custom step defined in the vars/dockerBuildPush.groovy file of your shared library.
• It encapsulates the logic for logging in, building, and pushing, keeping the main Jenkinsfile incredibly clean and readable.
• If you need to change how the build works, you update the library once, and all pipelines using it are updated automatically.

Important Tips

Tip

Use Shared Libraries for logic that is repeated across many different pipelines to reduce code duplication and maintenance burden.

Quick Quiz

Quick Quiz

#

What is the main benefit of using Jenkins Shared Libraries?

To reuse code across multiple pipelines and keep them DRY (Don't Repeat Yourself)

To use different versions of Jenkins

To run pipelines faster

To access the file system

Shared Libraries allow you to encapsulate common patterns and logic, making your Jenkinsfiles cleaner and easier to maintain.

#

Which annotation is used to import a library in a Jenkinsfile?

@Library('library-name')

@Import('library-name')

@Include('library-name')

@Require('library-name')

The @Library annotation tells Jenkins to load the specified library for use in the pipeline.

#

Where are global variables (custom steps) typically defined in a shared library structure?

vars/ directory

src/ directory

resources/ directory

lib/ directory

The vars directory contains scripts that are exposed as global variables (or custom steps) in pipelines.

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