I got answer for this query. This is because the added jar overrides my internal jars in apache tomcat. And I am using older tomcat that have not websocket-api.jar
So My solution for this problem is either use glashfish 4.x or else use apache tomcat 8.x that gives us required jar to run websocket. No need to add any extra websocket api jar.
再不加包得情况下，我用 tomcat9 能正常跑起来