In my example above I had spring.boot.starter.web on the classpath and the app failed to start. If I add org.apache.tomcat.embed.core then the application starts successfully.
When I configured module-info.java this way
requires spring.boot;
requires spring.boot.autoconfigure;
requires spring.web;
requires spring.boot.starter.web;
2021-05-20 10:56:09.501 INFO 17112 --- [ main] com.example.police.PoliceApplication : Starting PoliceApplication using Java 11 on zhaozhiguang-pc with PID 17112 (D:\item\police\target\classes started by zhaozhiguang in D:\item\police)
2021-05-20 10:56:09.501 INFO 17112 --- [ main] com.example.police.PoliceApplication : No active profile set, falling back to default profiles: default
2021-05-20 10:56:10.565 INFO 17112 --- [ main] com.example.police.PoliceApplication : Started PoliceApplication in 1.435 seconds (JVM running for 3.153)
Process finished with exit code 0
My guess is that Tomcat didn't boot
or
requires spring.boot;
requires spring.boot.autoconfigure;
requires spring.web;
requires org.apache.tomcat.embed.core;
This one worked
2021-05-20 10:57:48.097 INFO 13740 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2021-05-20 10:57:48.334 INFO 13740 --- [ main] o.s.b.a.e.web.EndpointLinksResolver : Exposing 2 endpoint(s) beneath base path '/actuator'
2021-05-20 10:57:48.381 INFO 13740 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2021-05-20 10:57:48.396 INFO 13740 --- [ main] com.example.police.PoliceApplication : Started PoliceApplication in 2.001 seconds (JVM running for 3.202)
2021-05-20 10:57:48.846 INFO 13740 --- [)-192.168.1.107] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-05-20 10:57:48.846 INFO 13740 --- [)-192.168.1.107] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2021-05-20 10:57:48.847 INFO 13740 --- [)-192.168.1.107] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
why?
spring.boot.starter.web depend on org.apache.tomcat.embed.core ?
Comment From: philwebb
Thanks for getting in touch, but it feels like this is a question that would be better suited to Stack Overflow. As mentioned in the guidelines for contributing, we prefer to use GitHub issues only for bugs and enhancements. Feel free to update this issue with a link to the re-posted question (so that other people can find it) or add some more details if you feel this is a genuine bug.