Maven，是一个Java开发比较常用的项目管理工具，可以对 Java 项目进行构建、依赖管理。
对于很多Java程序员来说，分层架构都是不陌生的，至少MVC三层架构都是不陌生的，甚至有人说："Any problem in computer science can be solved by anther layer of indirection."
In systems design, a fail-fast system is one which immediately reports at its interface any condition that is likely to indicate a failure. Fail-fast systems are usually designed to stop normal operation rather than attempt to continue a possibly flawed process. Such designs often check the system’s state at several points in an operation, so any failures can be detected early. The responsibility of a fail-fast module is detecting errors, then letting the next-highest level of the system handle them.
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