问题：Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean.

初次使用IDEA自带的Tomcat时，在maven中添加坐标，应修改scope的值为compile

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
</dependency>

应修改为：

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>compile</scope>
</dependency>