servlet上传期间的异常

Question

我想插入一个文件但总是失败并显示“Exception - ＆gt; null”。我应该在代码中更改什么才能正常运行？

@WebServlet(name="ServletFileUpload", urlPatterns={"/ServletFileUpload"})     // specify urlPattern for servlet
@MultipartConfig(location="C:\\Users\\Hitesh\\Documents\\NetBeansProjects\\MajorProject\\build\\web")                                                  // specifies servlet takes multipart/form-data
public class ServletFileUpload extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            // get access to file that is uploaded from client
            Part p1 = request.getPart("file");
            InputStream is = p1.getInputStream();

            // read filename which is sent as a part
            Part p2  = request.getPart("photoname");
            Scanner s = new Scanner(p2.getInputStream());
            String filename = s.nextLine();    // read filename from stream

            // get filename to use on the server
            String outputfile = this.getServletContext().getRealPath(filename);  // get path on the server
            FileOutputStream os = new FileOutputStream (outputfile);
            // write bytes taken from uploaded file to target file
            int ch = is.read();
            while (ch != -1) {
                 os.write(ch);
                 ch = is.read();
            }
            os.close();
            out.println("<h3>File uploaded successfully!</h3>");
        }
        catch(Exception ex) {
           out.println("Exception -->" + ex.getMessage());
        }
        finally { 
            out.close();
        }
    } 
 }