错误描述：启动没问题无报错
访问URL信息如下：
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Tue Oct 26 09:40:52 CST 2021
There was an unexpected error (type=Not Found, status=404).
控制台信息：
2021-10-26 09:40:51.965 INFO 644 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-10-26 09:40:51.965 INFO 644 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2021-10-26 09:40:51.965 INFO 644 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 0 ms
错误原因：
SpringBoot的启动类路径问题
SpringBoot的启动类要和Controller同级或在Controller上级