questo è invaliduser.java:
package usecc;
import java.lang.Exception;
public class invaliduser extends Exception {
public invaliduser(String message){
super(message);
}
}
e questo il .jsp:
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPor t()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'eccezioni.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
<%@ page import="usecc.*"%>
<%! void checkuser(String user) throws invaliduser {
if(user.length()<4)
throw new invaliduser("nome troppo breve");
} %>
<% String user = request.getParameter("user");
try {
if(user!=null) checkuser (user);
} catch(invaliduser e) { %>
nome troppo breve
<% }
%>
Login
<form action=eccezioni.jsp method=post>
user: <input type=text name=user>

<input type=submit value=login>
</form>
</body>
</html>
nell'head quelle cose me le inserisce eclipse