How to build docker images using a Declarative Jenkinsfile

You can use scripted pipeline blocks in a declarative pipeline as a workaround

pipeline {
    agent any
    stages {
        stage('Build image') {
            steps {
                echo 'Starting to build docker image'

                script {
                    def customImage = docker.build("my-image:${env.BUILD_ID}")
                    customImage.push()
                }
            }
        }
    }
}

I'm using following approach:

steps {
   withDockerRegistry([ credentialsId: "<CREDENTIALS_ID>", url: "<PRIVATE_REGISTRY_URL>" ]) {
      // following commands will be executed within logged docker registry
      sh 'docker push <image>'
   }
}

Where:

• CREDENTIALS_ID stands for key in Jenkis under which you store credentials to your docker registry.
• PRIVATE_REGISTRY_URL stands for url of your private docker registry. If you are using docker hub then it should be empty.

I cannot recommend the declarative syntax for building a Docker image bcos it seems that every important step requires falling back to the old scripting syntax. But if you must, a hybrid approach seems to work.

First a detail about the scm step: when I defined the Jenkins "Pipeline script from SCM" project that fetches my Jenkinsfile with a declarative pipline from git, Jenkins cloned the repo as the first step in the pipeline even tho I did not define a scm step.

For the build and push steps, I can only find solutions that are a hybrid of old-style scripted pipeline steps inside the new-style declarative syntax. For example see gustavoapolinario's work at Medium:

https://medium.com/@gustavo.guss/jenkins-building-docker-image-and-sending-to-registry-64b84ea45ee9

which has this hybrid pipeline definition:

pipeline {
  environment {
    registry = "gustavoapolinario/docker-test"
    registryCredential = 'dockerhub'
    dockerImage = ''
  }
  agent any
  stages {
    stage('Cloning Git') {
      steps {
        git 'https://github.com/gustavoapolinario/microservices-node-example-todo-frontend.git'
      }
    }
    stage('Building image') {
      steps{
        script {
          dockerImage = docker.build registry + ":$BUILD_NUMBER"
        }
      }
    }
    stage('Deploy Image') {
      steps{
        script {
          docker.withRegistry( '', registryCredential ) {
            dockerImage.push()
          }
        }
      }
    }
    stage('Remove Unused docker image') {
      steps{
        sh "docker rmi $registry:$BUILD_NUMBER"
      }
    }
  }
}

Because the first step here is a clone, I think he built this example as a standalone pipeline project in Jenkins (not a Pipeline script from SCM project).