org.apache.jasper.JasperException: java.lang.NumberFormatException: null

J'ai exception: org.apache.jasper.JasperException: java.lang.NumberFormatException: null
lorsque vous essayez ce code:

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<h3>Tanggal sekarang:</h3>
<%= new java.util.Date() %>
<% //begin scriplet
String nama = request.getParameter( "namadepan" );
String id = request.getParameter("idUser");
int idInt = Integer.parseInt(id);
if(nama!=null) {
%> <%-- end scriplet to insert fixed template data --%>
<h3>Halo <%= nama %>, <br/>
int idInt = Integer.parseInt(idUser);
Selamat datang di web Koperasi Aneka Usaha!
id anda :<%=idInt %>
</h3>
<% //continue scriptlet
}//end if
else {
%> <%-- end scriplet to insert fixed template data --%>
<form name="login" action="index.jsp" method="post">
<table width="200" border="1">
<tr>
<td width="56">Nama </td>
<td width="128"><input type="text" name="namadepan"></td>
</tr>
<tr>
<td>ID</td>
<td><input type="text" name="idUser"></td>
</tr>
<tr>
<td>Umur</td>
<td><input type=int name="umur"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" name="Submit" value="Submit"></td>
</tr>
</table>
</form>
<% //continue scriptlet
}//end else
%> <%-- end scriplet --%>
</body>
</html>

Comment réparer cette exception? im certain que l'erreur est d'environ convertint d'entrée de type string (idUser) à l'entier.

InformationsquelleAutor inggar | 2011-09-19