layout	title	folder	permalink	categories	tags
pattern	Mediator	mediator	/patterns/mediator/	Behavioral	Gang Of Four Decoupling

Intent

Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.

Class diagram

Applicability

Use the Mediator pattern when

• a set of objects communicate in well-defined but complex ways. The resulting interdependencies are unstructured and difficult to understand
• reusing an object is difficult because it refers to and communicates with many other objects
• a behavior that's distributed between several classes should be customizable without a lot of subclassing

Real world examples

• All scheduleXXX() methods of java.util.Timer
• java.util.concurrent.Executor#execute()
• submit() and invokeXXX() methods of java.util.concurrent.ExecutorService
• scheduleXXX() methods of java.util.concurrent.ScheduledExecutorService
• java.lang.reflect.Method#invoke()

Credits

• Design Patterns: Elements of Reusable Object-Oriented Software
• Head First Design Patterns: A Brain-Friendly Guide