1. Background
Links: https: //www.cnblogs.com/Agui520/p/11187972.html
https://blog.csdn.net/fd2025/article/details/79863390
To cover, under the single electricity supplier as an example. A electricity supplier system contains several categories of modules, such as users on module, product module, inventory module, order module, payment module, the logistics module, events module, the following will first list some of the most basic common module (user module commodity module, inventory module, order module, payment module).
