Some code about java reflection

@WebServlet("/ReflectServlet")
public class ReflectServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    @Override
    public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String method = req.getParameter("method");
        System.out.println(method);
        //Instantiate the Class class object, the servlet is instantiated at the time of request
        Class<?> clazz = this.getClass();    
        try {
            if (method == null) {
                method="toStart";
                //return a method object
                Method means = clazz.getMethod(method,HttpServletRequest.class,HttpServletResponse.class);
                //Call the method, pass in the instance of the calling method, the parameter list
                means.invoke(this,req,resp);
            }else {
                //return a method object
                Method means = clazz.getMethod(method,HttpServletRequest.class,HttpServletResponse.class);
                //Call the method, pass in the instance of the calling method, the parameter list
                means.invoke(this,req,resp);
            }
        } catch (Exception e) {
            e.printStackTrace ();
        }
    }
}