Servlet jsp null pointer exception

Question

Basically I have this function that allows people to search for other user based on their usernames. You type into the textbox id="search" and it will look for users with that username/similar username:

<form name="searchForm" action="searchUser"  method="post">
<input type="text" id="search" name="search" placeholder="Search.." />
<input type="submit" id="searchButton" name="searchButton" value="Search!" onclick="searchUsers()"/>
</form>

This is the servlet SearchUserServlet that maps to the action searchUser.The static method searchUser(string) returns an arraylist of user objects. I am trying to pass this arraylist to QuickMatchResult.jsp:

public class SearchUserServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
    public void doPost(HttpServletRequest request, HttpServletResponse response){

        try {

            String name=request.getParameter("search");
       ArrayList<User> userList=  User.searchUser(name);



            RequestDispatcher dispatcher=request.getRequestDispatcher("/QuickMatchResult.jsp");
            request.getSession().setAttribute("userList",userList);
            dispatcher.forward(request, response);
        } catch (ServletException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }catch(Exception e){
            e.printStackTrace();
        }
    }

This is the QuickMatchResult.jsp where it is forwarded. I'm trying to show all the usernames of the user objects in the arraylist:

<table id="searchResults">
<%      ArrayList<User> userList= new ArrayList<User>();
userList=(ArrayList<User>)request.getAttribute("userList");
for (int i=0; i<userList.size();i++){
User user=userList.get(i);
%>
<tr>
<td><%=user.getUserName()%></td>    
</tr>
<%

}
%>
</table>

However when I try to run this, I get a null pointer exception. Any idea why?

Read the userlist in jsp from session instead of request as you are setting the userlist in session — Vasu, Jun 19 '13 at 13:11

Prasad Kharkar · Answer 1 · 2013-06-19T13:17:21.290

0

You have set your attribute in the session and not in request. Use

request.setAttribute("userList", userList);

or if you want to use session, then retrieve the session attribute in JSP.

session.getAttribute("userList");

We get NullPointerException when we are trying to call a method on the object reference which does not refer to object. i.e. null.

In your case, you are trying to retrieve an attribute named userList from the request object, but there is no any attribute as such in request. If getAttribute does not find the attribute, it returns null

edited Jun 19 '13 at 13:17

answered Jun 19 '13 at 13:04

Prasad Kharkar

13,410
5
37
56

Thanks mate! I had it like that initially but it didn't work. – Blaiz Jun 19 '13 at 13:10
i think he is setting it in session itself – ajay.patel Jun 19 '13 at 13:10
@zerocool can you provide details about the problem? at which line you are getting NullPointerException and on what variable? I need more information – Prasad Kharkar Jun 19 '13 at 13:13
@zerocool sorry the message was meant for .Blaiz, can you provide full stacktrace? it would help us help you – Prasad Kharkar Jun 19 '13 at 13:16
Haha, thats what i was wondering :) @Blaiz check my post try it and if still doesnt work, put the stacktrace as Prasad is asking – ajay.patel Jun 19 '13 at 13:18

ajay.patel · Answer 2 · 2013-06-19T13:15:49.807

0

You are putting the userList in sesion object and trying to retrieve it from request object. Get this list from session not from the request.Below should help

userList=(ArrayList<User>)session.getAttribute("userList");

edited Jun 19 '13 at 13:15

answered Jun 19 '13 at 13:10

ajay.patel

1,957
12
15

Servlet jsp null pointer exception

2 Answers2