# 应用程序分层，保持Express在其边界内

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 ### 将组件代码分成web, services, DAL层
![alt text](../../assets/images/structurebycomponents.PNG "Separate component code into layers")

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### 1分钟说明：混合层的缺点
![alt text](../../assets/images/keepexpressinweb.gif "The downside of mixing layers")