Exception in Servlet

[Kudret Serin]

Hi all,
Why do i get following exception? (The Servlet compiles fine)

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Unknown Source)
java.lang.Integer.parseInt(Unknown Source)
com.ex.web.Topla.doPost(Topla.java:15)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.11 logs.

And the servlet is:

  
package com.ex.web;
 
import com.ex.model.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
 
public class Topla extends HttpServlet{

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

String sayi1=request.getParameter("sayi1");
String sayi2=request.getParameter("sayi2");

int toplam=Integer.parseInt(sayi1)+Integer.parseInt(sayi2);

request.setAttribute("toplam",toplam);

RequestDispatcher view=request.getRequestDispatcher("result.jsp");

view.forward(request,response);
}
}

[Paul Clapham]

If there is no sayi1 parameter in the request, then request.getParameter("sayi1") returns null. Since converting null to an int is meaningless, Integer.parseInt(sayi1) throws that exception.

You should put some logic in that code that does things differently if there is no sayi1 (or no sayi2) parameter in the request.

[Caine Lai]

Such as:

String sayi1=request.getParameter("sayi1");
String sayi2=request.getParameter("sayi2");
if (sayi1 != null && sayi2 != null) {
   int toplam=Integer.parseInt(sayi1)+Integer.parseInt(sayi2);
   request.setAttribute("toplam",toplam);
}
else {
   request.setAttribute("validationError", "sayi1 or sayi2 not found in request.");
}

[ December 22, 2005: Message edited by: Caine Lai ]

[Kudret Serin]

i made a typo in html file so that the servlet can not get the parameters from the request.
Dummy mistake:

...
Number 1: <input type="text name="sayi1"><br>
Number 2: <input type="text name="sayi2">
...

Thanks for the replies.