Implementation details

In this section, we'll look at how Tomcat implements the Engine component. This image describes the key elements of an engine's relationships.

Every Tomcat container implements the org.apache.catalina.Container interface. The org.apache.catalina.core.ContainerBase class is provided as a convenience to container implementers. It not only provides default implementations for the methods in the Container interface, but also implements other interfaces, such as the org.apache.catalina.Lifecycle and the org.apache.catalina.Pipeline interfaces that are critical for the functioning and administration of a container.

StandardEngine

The org.apache.catalina.core.StandardEngine class is the default implementation of the org.apache.catalina.Engine interface. This class extends the abstract base class ContainerBase, and so conveniently inherits a lot of the common functionality of a container.

An Engine may only contain children that are Host instances. Its addChild(Container) override...