pom的依赖问题

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
</dependency>

为什么我在pom中配置以上信息, 项目能够启动起来, 但是配置成和老师的一样就会出问题

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

org.springframework.context.ApplicationContextException: Unable to start reactive web server; nested exception is org.springframework.context.ApplicationContextException: Unable to start ReactiveWebApplicationContext due to missing ReactiveWebServerFactory bean.

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:76) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:544) ~[spring-context-5.0.8.RELEASE.jar:5.0.8.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:61) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:762) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:398) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:330) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1258) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246) [spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at com.zn.firstappdemo.FirstAppDemoApplication.main(FirstAppDemoApplication.java:12) [classes/:na]

Caused by: org.springframework.context.ApplicationContextException: Unable to start ReactiveWebApplicationContext due to missing ReactiveWebServerFactory bean.

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.getWebServerFactory(ReactiveWebServerApplicationContext.java:125) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.createWebServer(ReactiveWebServerApplicationContext.java:99) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.onRefresh(ReactiveWebServerApplicationContext.java:73) ~[spring-boot-2.0.4.RELEASE.jar:2.0.4.RELEASE]

... 8 common frames omitted