code: public void doHello( StaplerRequest request, StaplerResponse response ) throws IOException, ServletException {
          System.out.println("Hello operation");
          request.setAttribute("systemTime",new Long(System.currentTimeMillis()));
  
          // it can generate the response by itself, just like
          // servlets can do so. Or you can redirect the client.
          // Basically, you can do anything that a servlet can do.
  
          // the following code shows how you can forward it to
          // another object. It's almost like a relative URL where '.'
          // corresponds to 'this' object.
          response.forward(this,"helloJSP",request);
      }
docs: Define an action method that handles requests to "/hello"
  (and below, like "/hello/foo/bar")
  
  <p>
  Action methods are useful to perform some operations in Java.