NullPointerException with Servlet

Question

I am calling a Servlet using its URL address. This is the URL I am typing

http://localhost:7001/ryan/olympics?action=selectCatalog&id=1

This is the Servlet's URL for sure; if I change the address I get

page not found

This is the code for the Servlet.

public class Servlet extends javax.servlet.http.HttpServlet
        implements javax.servlet.Servlet {

private static final long serialVersionUID = 1L;

public Servlet() {
    super();
}

public void init(ServletConfig config) throws ServletException {
    System.out.println("*** initializing controller servlet.");
    super.init(config);
}

protected void doPost(HttpServletRequest request,
  HttpServletResponse response) throws ServletException, IOException {


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



if (action.equals("selectCatalog")) {
      String categoryId = request.getParameter("id");

      ProductModelDAO dao4 = new ProductModelDAOImpl("jpac");
      if (categoryId != null && !categoryId.trim().equals("")) {
          CategoryDAO dao1 = new CategoryDAOImpl("jpac");

    try {
        Category category = dao1.getCategoryName(categoryId);
        request.setAttribute("category", category);
        } catch (Exception e) {
        e.printStackTrace();
        }
    }

    try {
        @SuppressWarnings("unchecked")
        List<Product> products = dao4
            .getProductsByCategory(categoryId);
        request.setAttribute("products", products);
    } catch (Exception e) {
        e.printStackTrace();
    }

    url = "SelectCatalog.jsp";

 RequestDispatcher requestDispatcher =
  getServletContext().getRequestDispatcher(url);
requestDispatcher.forward(request, response);

I get the NullPointerException pointing to the RequestDispatcher's line. Any help?

Where under the `webapp` (or equivalent) folder is `SelectCatalog.jsp`? — Matt Ball, Nov 04 '12 at 16:42
CAMOBAP Thanks a lot. That was causing the error. Post your reply as an answer so I can mark it if you would like to. Thanks again!! — RonaDona, Nov 04 '12 at 16:45

CAMOBAP · Accepted Answer · 2012-11-04T17:19:00.090

3

Try changing "SelectCatalog.jsp" to "/SelectCatalog.jsp", because, as I understand, You want to use an absolute path.

edited Nov 04 '12 at 17:19

answered Nov 04 '12 at 16:51

CAMOBAP

5,523
8
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score 0 · Answer 2 · answered Nov 04 '12 at 17:25

0

If you want to use a relative path you have to use:

request.getRequestDispatcher(url);

in place of:

getServletContext().getRequestDispatcher(url);

answered Nov 04 '12 at 17:25

thedayofcondor

3,860
1
19
28

score 0 · Answer 3 · answered Aug 12 '13 at 05:48

0

request.getParameter("action");

code is written in doPost method. Are you invoking this servlet from doPost method of calling servlet? URL parameters will not be used by doPost method.

answered Aug 12 '13 at 05:48

user2670556

31
1

NullPointerException with Servlet

3 Answers3