Setting List as an attribute in servlet and retrieving in JSP

Question

I am attempting to set a list of integers to an attribute within a servlet, and then retrieve the list in the redirected JSP page.

I have looked at previous answers here and here, as well as others, and my code seems identical to the answers to me. Obviously I have done something wrong but I can't see the issue.

Please note that the "accomList" is set correctly in the servlet as I have tested this by outputting the list to the console in the servlet. It is set to [1,2,3,4,21].

"AccomSearch.java" Servlet

session.setAttribute("accomList",accomList);//set list as attribute
getServletConfig().getServletContext().getRequestDispatcher("/viewAccom.jsp").forward(request,response); // redirect to jsp page

^ Setting the "accomList" list to an attribute and redirecting the user to the jsp page.

"viewAccom.jsp" JSP Page

 <%
           List<Integer> accomList = new ArrayList<>();
           accomList = (List<Integer>) request.getAttribute("accomList");
           if (accomList==null){
              out.println("accomList is null, Why is the list null?");
           }else{
              for (int i = 0; i < accomList.size(); i++) {
                   out.println(Integer.toString(accomList.get(i)));
               }
           }

        %>

^ Attempting to retrieve the "accomList" attribute, cast it to a list, then display it.

When the code is run the "accomList" variable in the JSP page returns as "Null". So the String "accomList is null, Why is the list null?" is displayed in the browser. This is not intended.

My guess is that I am either setting or retrieving the attribute incorrectly. Thanks in advance for any help you can spare.

Also, This is my first stackOverflow question, so let me know if I have posted this in the wrong area, or the formatting is bad, etc.

score 1 · Accepted Answer · answered Mar 21 '16 at 15:30

1

you have to set the List in the request not the session:

request.setAttribute("accomList",accomList);//set list as attribute

or you change the jsp code to:

accomList = (List<Integer>) request.getSession().getAttribute("accomList");

because currently you set the List into the user session.

answered Mar 21 '16 at 15:30

nano_nano

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1

How did I not see that... Thanks a lot. i think i'm overworked. xD – Stevis Andrea Mar 21 '16 at 15:36
you can get the list using expression language in the jsp as ${accomList} – Richard Elite Mar 21 '16 at 18:08

score 0 · Answer 2 · answered Jul 31 '20 at 09:06

you can use request object also instead of session like below example.

-> student.java

 List<String> studentNameList=new ArrayList<>();
   studentNameList.add("Rohan");
   studentNameList.add("Arjun");
   request.setAttribute("studentNameList",studentNameList);

-> student.jsp

 List<String> studentNameList= (List<String>) request.getAttribute("studentNameList");

Setting List as an attribute in servlet and retrieving in JSP

2 Answers2