HttpSession session = request.getSession();   //it’s also same syntax to get existing session

set cookie:

Cookie c = new Cookie(name, value);
response.addCookie(c);

Seems like you can get cookie from 

Cookie[] cookies = request.getCookies();
for (int i = 0; i < cookies.length; i++) {
            Cookie c = cookies[i];
            String name = c.getName();
            String value = c.getValue();
            out.println(name + “ = ” + value);
        }