How to publish a docker image to a private docker registry using Jenkins' blueocean?

It seems that the syntax that is used in the pipeline plugin is incompatible with Blueocean. It looks like that the syntax is different as blueocean uses a declarative pipeline.

Example

http://fishi.devtail.io/weblog/2016/11/20/docker-build-pipeline-as-code-jenkins/

stage ('Docker Build') {
    // prepare docker build context
    sh "cp target/project.war ./tmp-docker-build-context"

    // Build and push image with Jenkins' docker-plugin
    withDockerServer([uri: "tcp://"]) {
      withDockerRegistry([credentialsId: 'docker-registry-credentials', url: "https:///"]) {
        // we give the image the same version as the .war package
        def image = docker.build("/:${branchVersion}", "--build-arg PACKAGE_VERSION=${branchVersion} ./tmp-docker-build-context")
        image.push()
      }   
    }
}

results in:

WorkflowScript: 5: Unknown stage section "sh". Starting with version 0.5, steps in a stage must be in a steps block. @ line 5, column 1.
   stage ('Docker Build') {
   ^

Attempt to solve the issue

When a steps block was added the pipeline failed again:

WorkflowScript: 13: Method calls on objects not allowed outside "script" blocks. @ line 13, column 13.
               docker.withRegistry

You can try to use scripting syntax into the declarative pipeline. For some step there is no declarative syntax yet. I had the same problem trying to use the docker global variable as a step.

stage ('Docker Build') {
  steps {
    // prepare docker build context
    sh "cp target/project.war ./tmp-docker-build-context"

    // Build and push image with Jenkins' docker-plugin
    script {
      withDockerServer([uri: "tcp://"]) {
        withDockerRegistry([credentialsId: 'docker-registry-credentials', url: "https:///"]) {
            // we give the image the same version as the .war package
            def image = docker.build("/:${branchVersion}", "--build-arg PACKAGE_VERSION=${branchVersion} ./tmp-docker-build-context")
            image.push()
        }
      }
    }
  }
}

StackExchange DevOps Q#2143, answer score: 6