Demo Declarative vs Scripted Pipeline

In this guide, we’ll explore the differences between Declarative and Scripted Jenkins Pipelines using two sample Jenkinsfiles stored in a Git repository. You’ll learn how each pipeline type handles source control, error handling, and post-build actions.

Repository Overview

Our Gitea repository declarative-vs-scripted-pipeline holds two pipeline definitions:

Jenkinsfile.declarative – a Declarative Pipeline
Jenkinsfile.scripted – a Scripted Pipeline

The image shows a Gitea repository interface for a project named "declarative-vs-scripted-pipeline" with two branches and files related to Jenkins pipelines.

Declarative Pipeline (`Jenkinsfile.declarative`)

A Declarative Pipeline uses a fixed, structured syntax that’s easy to read and maintain. Here’s a minimal example:

pipeline {
    agent any

    stages {
        stage('Echo Message') {
            steps {
                sh 'ls -ltr'
                sh 'echo "This is executed within a DECLARATIVE Pipeline"'
            }
        }
    }

    post {
        always {
            sh 'echo "This will always run"'
            sh 'rm -rf *'
        }
    }
}

Key features of Declarative Pipelines:

Built-in SCM Checkout via an automatic stage
Structured Syntax: pipeline, agent, stages, post
Stage Restarts: rerun from any completed stage

Scripted Pipeline (`Jenkinsfile.scripted`)

Scripted Pipelines require you to explicitly call checkout scm if you need source files. They do not include automatic SCM checkout.

A Scripted Pipeline offers full Groovy flexibility. Here’s a basic example without SCM checkout:

node {
    try {
        stage('Echo Message') {
            sh 'ls -ltr'
            sh 'echo This is executed within a SCRIPTED Pipeline'
        }
    } catch (err) {
        echo "Failed: ${err}"
    } finally {
        sh 'echo "This will always run."'
        // sh 'rm -rf *'
    }
}

1. Configuring a Declarative Pipeline Job

In the Jenkins dashboard, click New Item, enter d-v-s-pipeline, select Pipeline, then OK.

The image shows a Jenkins interface for creating a new item, with options to select different project types such as Freestyle project, Pipeline, Multi-configuration project, and Folder. The user has entered "d-v-s-pipeline" as the item name.

Under Pipeline, choose Pipeline script from SCM, then set:
- SCM: Git
- Repository URL and Credentials
- Branch: demo-1
- Script Path: Jenkinsfile.declarative

The image shows a Jenkins configuration screen for setting up a pipeline, with options for specifying the SCM, repository URL, credentials, and branch to build.

Click Apply & Save, then Build Now. In Blue Ocean or the classic pipeline view, you’ll see:
- (Declarative: Checkout SCM)
- Echo Message
- (Declarative: Post Actions)

The image shows a Jenkins configuration screen for a pipeline, with options to specify branches, repository browser, and script path. There are buttons for saving and applying changes.

Sample Declarative Pipeline Logs

Checking out Revision abcdef12345 (origin/demo-1)
[Pipeline] stage (Echo Message)
[Pipeline] sh
+ ls -ltr
Jenkinsfile.declarative  Jenkinsfile.scripted
[Pipeline] sh
+ echo This is executed within a DECLARATIVE Pipeline
This is executed within a DECLARATIVE Pipeline
[Pipeline] stage (Declarative: Post Actions)
[Pipeline] sh
+ echo This will always run
This will always run
[Pipeline] sh
+ rm -rf *

2. Running the Scripted Pipeline

Edit the job’s Script Path to Jenkinsfile.scripted and start a new build. Since we haven’t added checkout scm, the build will:

Execute Echo Message without listing repository files
Run the finally block for cleanup

The image shows a Jenkins dashboard displaying the status of a pipeline named "d-v-s-pipeline," with stages like "Start," "Echo Message," and "End." It includes build history and permalinks for recent builds.

Sample Scripted Pipeline Logs (without checkout)

+ ls -ltr
(total 0)
+ echo This is executed within a SCRIPTED Pipeline
This is executed within a SCRIPTED Pipeline
+ echo This will always run
This will always run

3. Key Differences

Pipeline Feature	Declarative Pipeline	Scripted Pipeline
SCM Checkout	Automatic `Checkout SCM` stage	Must add `checkout scm` explicitly
Syntax	Structured DSL (`pipeline`, `stages`, `post`)	Free-form Groovy (`node`, `try-catch-finally`)
Restart from Stage	Supported	Not supported
Post Actions	Built-in `post` block (`always`, `success`, etc.)	Implement via `finally` block

4. Enabling SCM Checkout in Scripted Pipeline

To include source checkout, update Jenkinsfile.scripted:

node {
    try {
        stage('Echo Message') {
            checkout scm
            sh 'ls -ltr'
            sh 'echo This is executed within a SCRIPTED Pipeline'
        }
    } catch (err) {
        echo "Failed: ${err}"
    } finally {
        sh 'echo "This will always run."'
        // sh 'rm -rf *'
    }
}

Commit your changes and rebuild. Now the pipeline will fetch your repository before running the stage:

The image shows a Jenkins dashboard displaying the status of a pipeline named "d-v-s-pipeline," with stages like "Start," "Echo Message," and "End." The interface includes options for configuring and managing the pipeline, along with build history and permalinks.

Sample Scripted Pipeline Logs (with checkout)

> git rev-parse --resolve-git-dir /var/lib/jenkins/workspace/d-v-s-pipeline/.git # timeout=10
> git fetch remote.origin.url http://... # timeout=10
> git checkout -f abcdef12345 # timeout=10
+ ls -ltr
Jenkinsfile.declarative  Jenkinsfile.scripted
+ echo This is executed within a SCRIPTED Pipeline
This is executed within a SCRIPTED Pipeline
+ echo This will always run
This will always run

Conclusion

Declarative Pipelines: Use for built-in SCM checkout, stage-level restarts, and a clear, opinionated syntax.
Scripted Pipelines: Opt for full Groovy control, but remember to manage SCM checkout and error handling manually.

Thank you for following this comparison of Declarative vs. Scripted Jenkins Pipelines!

Introduction and Basics

Jenkins Setup and Interface

Extending Jenkins and Administration

Jenkins Pipelines

Automation and Security

Setting up CI Pipeline

Code Quality and Testing

Containerization and Deployment

Kubernetes and GitOps

AWS Lambda and Advanced Deployment Techniques

Jenkins Administration and Monitoring - Part 1

Shared Libraries in Jenkins

Agents and Nodes in Jenkins

Pipeline Enhancement and Caching

Pipeline Structure and Scripted vs Declarative

Jenkins Administration and Monitoring - Part 2

Backup and Configuration Management

Demo Declarative vs Scripted Pipeline

Repository Overview

Declarative Pipeline (`Jenkinsfile.declarative`)

Scripted Pipeline (`Jenkinsfile.scripted`)

1. Configuring a Declarative Pipeline Job

Sample Declarative Pipeline Logs

2. Running the Scripted Pipeline

Sample Scripted Pipeline Logs (without checkout)

3. Key Differences

4. Enabling SCM Checkout in Scripted Pipeline

Sample Scripted Pipeline Logs (with checkout)

Conclusion

Links and References

Watch Video

​Repository Overview

​Declarative Pipeline (Jenkinsfile.declarative)

​Scripted Pipeline (Jenkinsfile.scripted)

​1. Configuring a Declarative Pipeline Job

​Sample Declarative Pipeline Logs

​2. Running the Scripted Pipeline

​Sample Scripted Pipeline Logs (without checkout)

​3. Key Differences

​4. Enabling SCM Checkout in Scripted Pipeline

​Sample Scripted Pipeline Logs (with checkout)

​Conclusion

​Links and References

Watch Video

Repository Overview

Declarative Pipeline (`Jenkinsfile.declarative`)

Scripted Pipeline (`Jenkinsfile.scripted`)

1. Configuring a Declarative Pipeline Job

Sample Declarative Pipeline Logs

2. Running the Scripted Pipeline

Sample Scripted Pipeline Logs (without checkout)

3. Key Differences

4. Enabling SCM Checkout in Scripted Pipeline

Sample Scripted Pipeline Logs (with checkout)

Conclusion

Links and References