facade 模式和gateway模式的区别

原文：http://stackoverflow.com/questions/4422211/what-is-the-difference-between-facade-and-gateway-design-patterns

Reviewing Facade in the GoF book and the link in another answer to Martin Fowler's Gateway, it appears that their focus is in opposite directions.

Facade provides a simple uniform view of complex internals to (one or more)external clients;

Gateway provides a simple uniform view of external resources to the internals of an application.

This distinction lets us focus on which is more important in a design :

With the Facade, the external system is our customer; it is better to add complexity facing inwards if it makes the external interface simpler.

With the Gateway, the internal system is our customer; give it all the help we can, even if the externals are more complex.