TriggerStep.java

public class TriggerStep extends AbstractStepImpl {

  private final String spec;

  @DataBoundConstructor
  public TriggerStep(String spec) {
    this.spec = spec;
  }

  public String getSpec() {
    return spec;
  }

  public static class Execution extends AbstractSynchronousStepExecution<Void> {
    private static final long serialVersionUID = 1L;

    @Inject
    transient TriggerStep step;
    @StepContextParameter
    transient Run<?,?> build;

    @Override
    protected Void run() throws Exception {
      Job<?,?> parent = build.getParent();
      if(parent instanceof WorkflowJob) {
        WorkflowJob job = (WorkflowJob) parent;
        job.addTrigger(new SCMTrigger(step.getSpec()));
        job.save();
      } else {
        throw new AbortException("cannot apply trigger to job of type " + parent.getClass().getSimpleName());
      }
      return null;
    }
  }

  @Extension
  public static class DiscriptorImpl extends AbstractStepDescriptorImpl {
    public DiscriptorImpl() {
      super(Execution.class);
    }

    @Override
    public String getFunctionName() {
      return "scmTrigger";
    }

    @Override
    public String getDisplayName() {
      return "Set an SCM Trigger for this project.";
    }
  }
}