Chain-of-responsibility pattern

A mechanism also exists for adding new processing objects to the end of this chain.

In a variation of the standard chain-of-responsibility model, some handlers may act as dispatchers, capable of sending commands out in a variety of directions, forming a tree of responsibility.

The chain-of-responsibility pattern is structurally nearly identical to the decorator pattern, the difference being that for the decorator, all classes handle the request, while for the chain of responsibility, exactly one of the classes in the chain handles the request.

However, many implementations (such as loggers below, or UI event handling, or servlet filters in Java, etc.)

The Receiver1, Receiver2, and Receiver3 classes implement the Handler interface by either handling or forwarding a request (depending on run-time conditions).