facade -- 对于有很多接口的提供一个简单的接口

Function:   

      A facade is an object that provides a simplified interface to a larger body of code, such as a class library. A facade can:

• make a software library easier to use and understand, since the facade has convenient methods for common tasks;
• make code that uses the library more readable, for the same reason;
• reduce dependencies of outside code on the inner workings of a library, since most code uses the facade, thus allowing more flexibility in developing the system;
• wrap a poorly-designed collection of APIs with a single well-designed API (as per task needs).

      An Adapter is used when the wrapper must respect a particular interface and must support a polymorphic behavior. On the other hand, a facade is used when one wants an easier or simpler interface to work with.

Actors:
      Facade, many other objects

Summary:
      put many other objects into a new class and then provide a method for service.