从页面到页面JSP检索映射属性

Question

i am trying to get retrieve attributes which are being put into a map. However i keep getting null when i try to debug it by putting it in an alert. Any help will be appreciated, thank you!

First jsp

<%
   //Map newSurvey = new LinkedHashMap();
   Map newSurvey = new HashMap();
   newSurvey.put("description", request.getParameter("description"));
   newSurvey.put("startDate", request.getParameter("start_datetime"));
   newSurvey.put("endDate", request.getParameter("end_datetime"));
   newSurvey.put("maxParticipant", request.getParameter("max_participant"));
   newSurvey.put("minAge", request.getParameter("min_age"));
   newSurvey.put("maxAge", request.getParameter("max_age"));
   newSurvey.put("preSurveyText",  request.getParameter("pre_survey_text"));
   request.setAttribute("myMap", newSurvey);
%>
window.location = 'Survey_Questions.jsp';

Second jsp (to retrieve) i used a javascript to see if i am able to retrieve it

function testGet(){
        <%
        Map myMap = (Map)request.getParameter("myMap");
        String description = (String) myMap.get("description");
        %>
        alert(<%=description%>
    }

Answer 1

On first page you are using: request.setAttribute("myMap", newSurvey); .

So you must have to use request.getAttribute("myMap"); on second page.

Answer 2

window.location = 'Survey_Questions.jsp';

Will just redirect to a page and it will not pass your request object to other documents.

Instead you can use below lines of code:

RequestDispatcher rd = request.getRequestDispatcher("Survey_Questions.jsp");
rd.forward(request, response);

RequestDispatcher helps you to forward your request to other pages.

Also, use getAttribute instead of getParameter as you have used setAttribute to set myMap on First.jsp.