Qfyilyi

I want to change the view from the HTML list to JSON data.

This my code in controller:-

private void listFeedback(HttpServletRequest request, HttpServletResponse response)

            throws SQLException, IOException, ServletException {

        Feedback p = new Feedback();

        int seller_id = Integer.parseInt(request.getParameter("seller_id"));

        List<Feedback> feedbacks = p.all(seller_id);

        String format = request.getParameter("format");

        if(format == "json"){

            String json = new Gson().toJson(feedbacks);



            response.setContentType("application/json");

            response.setCharacterEncoding("UTF-8");

            response.getWriter().write(json);

            RequestDispatcher dispatcher = request.getRequestDispatcher("feedbacks/demo.jsp");

            dispatcher.forward(request, response);

        }

        request.setAttribute("feedbacks", feedbacks);

        RequestDispatcher dispatcher = request.getRequestDispatcher("feedbacks/list.jsp");

        dispatcher.forward(request, response);

    }

But, It can be still viewed like before, nothing got to change at all. I wish it to be redirected to demo.jsp so that it can have a JSON view. Would anyone help me doing the same?

UPDATE

I just forget to put else in there
so, this the right code

else{

    request.setAttribute("feedbacks", feedbacks);

            RequestDispatcher dispatcher = request.getRequestDispatcher("feedbacks/list.jsp");

            dispatcher.forward(request, response);

}

Thank you so much for answering my question.

It looks format value is null or not json. If the code present inside if executed, you would end up having error (The next lines of code, you are forwarding to another jsp).

"Cannot forward after response has been committed"

Make the below changes to make it work:

you would not need to forward while you wanted to return the JSON. just add below code inside if

if("json".equals(format)){

                String json = new Gson().toJson(feedbacks);

                response.setContentType("application/json");

                response.setCharacterEncoding("UTF-8");

                response.getWriter().write(json);

                return; // return from here or change to if-else

}

The whole code:

    private void listFeedback(HttpServletRequest request, HttpServletResponse response)

                throws SQLException, IOException, ServletException {

            Feedback p = new Feedback();

            int seller_id = Integer.parseInt(request.getParameter("seller_id"));

            List<Feedback> feedbacks = p.all(seller_id);





      String format = request.getParameter("format");

        if("json".equals(format)){

            String json = new Gson().toJson(feedbacks);

            response.setContentType("application/json");

            response.setCharacterEncoding("UTF-8");

            response.getWriter().write(json);

            return;// return from here or change to if-else

        }

        request.setAttribute("feedbacks", feedbacks);

        RequestDispatcher dispatcher = request.getRequestDispatcher("feedbacks/list.jsp");

        dispatcher.forward(request, response);

    }