Error message:
Unable to start web server; nested exception is org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat
Cause Analysis:
1. Check whether the wrong file is added to your pom or conflicts occur.
This is because I added the wrong project and reported an error.
2. Or your own files are not added to the compiled file. Just clean maven and then restart.
3. Check whether the annotation @SpringBootApplication is added to the startup class
