How compose web.xml to lauch server side with maven and jetty

What should I put into web.xml to launch to start server side. I launch jetty but only ui works server side isn't not running

I have next folder tree:

src
  |-main
      |-java
      |    |-com
      |        |-example
      |                |-test
      |                     |-ServerSide.java
      |-webapp
             |-index.html
             |-WEB-INF
                     |-web.sml