Automatically trigger Jenkins Pipeline on Gitlab push

Imagine you have your git repository hosted on Gitlab, and want to automatically trigger a Jenkins pipeline to build your code when you push on a given branch, for example "develop".

Here are the steps to follow.

1) Download Gitlab plugin for Jenkins.

Project repository is here: https://github.com/jenkinsci/gitlab-plugin#webhook-url

2)Create a new pipeline on Jenkins.

In this example we named the pipeline "my-pipeline"

When configuring the pipeline, set a webhook on Jenkins as shown here:

3) Set Jenkins Integration in Gitlab.

Go in your project repository, and configure the integration like here:

As you can see, the Secret token is the same shown on Jenkins Build Trigger.

4) Create a Jenkins user on Gitlab to clone the repository.

Create the user and then add it as a Developer in your project.

5) Create a Credential set for Jenkins user on Jenkins server.

In Jenkins, go to Credentials, and add a new Credential like this:

6) Add a clone step to your pipeline using the credential just created.

stage('Clone sources') {

  steps {

    git credentialsId: 'gitlab-jenkins-user', branch: 'develop', url: 'https://my.gitlab.org/test.git'

  }        

}