1. Initial failed to start, the thought is springboot 1.x and 2.x versions of different leads, version 2.x success, 1.x version, in fact, regardless of the version
2. Note that the main function entry file must be in the src / main, and must be at the same level or higher controller.java package, i.e., the file tree is deeper than the main function controller
3. The primary function entry can not forget (class must be the class where, because of this error directly copy the code, the corresponding .class forget to change the class name)
