Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.

照着教程弄的第一个 DEMO，结果启不来。

解决办法：在Controller 上面加上 @EnableAutoConfiguration 

成功启动

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Demo的其它内容及配置如下图，新建一个 空的 Maven 项目

Pom.xml

 主界面：

Control.java

运行报错

 :: Spring Boot ::        (v2.2.5.RELEASE)

2020-03-06 08:41:45.942  INFO 8240 --- [           main] com.iron.HelloWorldMainApp               : Starting HelloWorldMainApp on ChenJun with PID 8240 (F:\Project\SpringBoot\sprintboot01helloworld\target\classes started by Jimmy in F:\Project\SpringBoot\sprintboot01helloworld)
2020-03-06 08:41:45.947  INFO 8240 --- [           main] com.iron.HelloWorldMainApp               : No active profile set, falling back to default profiles: default
2020-03-06 08:41:46.152  WARN 8240 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
2020-03-06 08:41:46.302 ERROR 8240 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.context.ApplicationContextException: Unable to start web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:156) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:544) ~[spring-context-5.2.4.RELEASE.jar:5.2.4.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at com.iron.HelloWorldMainApp.main(HelloWorldMainApp.java:11) [classes/:na]
Caused by: org.springframework.context.ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.getWebServerFactory(ServletWebServerApplicationContext.java:203) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.createWebServer(ServletWebServerApplicationContext.java:179) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:153) ~[spring-boot-2.2.5.RELEASE.jar:2.2.5.RELEASE]
	... 8 common frames omitted


Process finished with exit code 1