如何将init参数传递给HttpSessionListener?

在代码中:

public class MyListener implements HttpSessionListener {

   public void sessionCreated(HttpSessionEvent event) {
      String value = event.getSession().getServletContext().getInitParameter(paramName);
   }
}

<web-app ...>
...
    <context-param>
        <param-name>my_param</param-name>
        <param-value>12345</param-value>
    </context-param>