The Builder class and Stapler

The first class is GravenBuilder.java. The class declares that it extends the Builder class:

public class GravenBuilder extends Builder {

As we can see in the JavaDoc at http://javadoc.jenkins-ci.org/hudson/tasks/Builder.html, extending the Builder class will register this class with Jenkins as a custom builder, which is what we are after.

Tip

This extension declaration is how the Extension point page is updated—the program that builds the index will find this reference in the code and automatically create the association for us.

The GravenBuilder class also contains this simple method:

@DataBoundConstructor
public GravenBuilder(String task) {
  this.task = task;
}

Through the use of the @DataBoundConstructor annotation, this method will register the selection of this task/build type when the user decides to create this new build type. This is done automatically via the Stapler framework, which Jenkins uses to serialize and convert Java objects. You can find out more...