springboot启动抛出javax.websocket.server.ServerContainer not available

问题描述：spring boot接入websocket时，启动报错：javax.websocket.server.ServerContainer not available

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

原因：因为spring boot内带tomcat，tomcat中的websocket会有冲突。
解决办法：spring boot启动时排除tomcat依赖包即可:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>