Design pattern of facade and mediator

### Mediator and facade design pattern Today, let's talk about two design patterns ： Mediator design pattern and facade design pattern , Why should they be explained together , Because they are so similar , It's just because of the place of action that different names come into being . We use one for us 90 Let's start with the most difficult question . Suppose we're tired of city life , Looking for a quiet place to live , Pig raising , By the way, write a pig face recognition to classify and manage these pigs. ( Life in dream ). And in the premise of doing these things , We must build a house and a pig pen. . Let's take a look at what we used to do .  Building a house requires workers , Brick , Cement and so on , We need one person to get in touch with . But I'm too smart to do that , So I got someone to help me with these things , So that's the process .  I found a contractor , The agent helps me with these things . This process is a complete facade pattern . Does it feel like a little bit of a proxy model , Help me with my work . In fact, the design pattern will reach the same goal in the end , So called , Taiji Sword technique , Learn how much and forget how much , The last thing I remember is Tai Chi sword . Let's go back to programming , Let's take a look at the specific class diagram implementation of facade pattern  Let's take a look at the design pattern of downloaders . The biggest difference between it and the facade is that the facade pattern is in the outer layer , And it's in the middle of all services . Let's take a look at the schematic diagram .  Let's take a look at its class diagram implementation  ** Did you find out , The class diagram implementations of the two patterns are almost the same , So their code implementation is almost the same .** After understanding their principles , Let's talk about their application in real code . ** Facade mode ：** Gateway for server deployment , Block all requests , The specific method of forwarding is decided by the gateway ** Mediator mode ：** Coordination intermediary software , Microservices register all services to the `zookeeper` In the mediation software , Accessing other services through mediation software ; Information intermediary software , What information need to be obtained through the message intermediary software . For some older projects , The scheduling center of facade mode and mediator mode is likely to be one , If passed `Nginx` Management services . Let's take a look at the specific code implementation . ** Code implementation of facade mode （ Role composition ）** - ** Subsystem ** ```java class Cement{ void cement(){ System.out.println(" cement "); } } class Worker{ void worker(){ System.out.println(" Worker "); } } class Brick{ void brick(){ System.out.println(" Brick "); } } ``` - ** Facade ** ```java class Contractor{ private Cement cement = new Cement(); private Worker worker = new Worker(); private Brick brick = new Brick(); void cement(){ cement.cement(); } void worker(){ worker.worker(); } void brick(){ brick.brick(); } } ``` The code implementation of mediator mode is almost the same as facade mode . The two are only born because of their response and different positions , Essentially the same . Please pay attention to the public account for more original articles @Ma