ideal中编译正常，说明类存在。但是启动报错

尝试添加 javax.servlet-api 很多版本的依赖，均无效。

<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
    <scope>provided</scope>
</dependency>

后尝试添加 如下依赖，问题解决

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-websocket</artifactId>
    <version>9.0.44</version>
</dependency>