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Before proceeding I realise that there's a similar question (Passing a List from Servlet to JSP) from a couple of years ago. I realise that it is possible to set the list I'm trying to pass as a session attribute but out of curiosity I wondered if it's possible to use the PrintWriter object to send the data back to the JSP page.

JSP

<script type="text/javascript">
        function getEngineSchemes(engineID) {
            $.get('SchemeTypeServlet', {
                action: "getSchemes",
                engineID: engineID
            },
            function(data, status){

            }).fail(function() {
                alert("Error obtaining schemes for engine with engine id: " + engineID);
            });
        }
    </script>
</body>

Servlet

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //Set type of response
    response.setContentType("text/html");
    response.setCharacterEncoding("UTF-8");
    //get parameters that may be passed from client to determine which methods should be called
    String action = request.getParameter("action");

    if(action.equalsIgnoreCase("getSchemesForEngine")) { 
        Integer engineID = Integer.parseInt(request.getParameter("engineID"));
        List<String> schemeNames = getSchemeNamesForEngine(engineID);

        response.getWriter(). //insert code to send object back to JSP
        response.getWriter().flush();
    }

Options

One solution I think may be reasonable would be to create a JSONObject and have something along the lines of 

response.setContentType("application/json");
JSONObject json = new JSONObject();
     for(String name : schemeNames) {
            json.put(engineID, name);
         }
    response.getWriter().write(json.toJSONString());
    response.getWriter().flush();

I haven't tested the above code but I just want to know if that seems like the best solution to my problem or if I'm making it overly complicated? Maybe there's a far simpler solution to my question.

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Scott Barbour
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1 Answers1

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I think you are having things messed up in your head. First of all, you cannot sent text or any kind of data from a servlet to a jsp. The proper way to do this is to use the session and use response.sendRedirect or RequestDispatcher.forward methods. But this will ignore any calls made before to the servlet's Writer Object.

MaVRoSCy
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  • Yes, you can send data from a Servlet back to the JSP page because I have done so already. In a JSP file you can include HTML and JavaScript and as such you can use JQuery.post() which allows you to specify a Servlet to post the data to, and in the callback function, for example: ... }).done(function( data ) { var content = data[.json_identifier] $( "#result" ).val(content); }); you can utilise your results obtained from the Servlet to populate html elements. – Scott Barbour Jan 22 '16 at 09:25