The architecture mode is excerpted from "happy when you smell defects" (this book can be downloaded for free)

There are many architectural patterns , Just three examples .

1. Layered architecture

The classic three-tier architecture is the best scenario , Database management software （ Add or delete check change ）, Most enterprise software is of this kind . The classic three-tier architecture consists of a top-down user interface layer 、 Business logic layer and data access layer .《 Domain-driven design 》 The layered architecture in ： User interface layer 、 application layer （ Provide the caller with a complete business use case ）、 Domain layer 、 Infrastructure layer .

Stratification is based on ： One , The top level is more business and user oriented , The bottom layer is more general and hardware oriented . Two , In the face of change . 3、 ... and , At the same level, at the same level of abstraction .

Be careful ： If most of the functions of a certain layer are simply calling the functions of the lower layer , This layer should be cancelled .

1. Event bus architecture

Three participants ： Event bus 、 Publisher 、 subscriber , Publishers can only send messages to the event bus , Event bus can only send messages to subscribers . Messages are also called events . This architecture is very suitable for distributed systems , Heterogeneous systems also have no impact . A module can be both a publisher and a subscriber .

The difference between time bus module and message queue module ： The former collects 、 Forward a message , You don't need to know how many subscribers there are ; The latter processes messages directly or forwards them to submodules . Message queuing has the advantage over message queuing ： asynchronous 、 Peak shaving . Advantages of messages over direct function calls ： decoupling .

1. Blackboard mode

Blackboard mode by 3 There are three main components ： blackboard ： Structured global memory containing objects from solution space . Knowledge source ： Specialized modules and their own representations . Control components ： choice 、 Configuration and execution modules . Use scenarios ： speech recognition 、 Vehicle identification and tracking 、 Protein structure recognition 、 Sonar signal interpretation, etc . This kind of problem has the following characteristics ： It can be decomposed into multiple subproblems , But each subproblem belongs to a different field of expertise . To solve the subproblem , You need to use different representations and paradigms , There is often no established strategy .