1. 和实例3差不多，唯一的区别是在LoginForm.java中多了对Cookie的调用，当你注册号了之后，第一次登陆时会出现提示语”This is the first time you have logged on”,以后每次登录都会告诉你登陆的次数，当你登陆到第五次时会出现"Congratulations!!!,You have a gife"
2. LoginForm.java的代码如下:
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.sql.*;
///import javax.sql.*;
public class LoginForm extends HttpServlet
{
Connection dbcon;
protected void doPost(HttpServletRequest req,
HttpServletResponse resp)
throws ServletException,
java.io.IOException
{
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
dbcon=DriverManager.getConnection("jdbc:odbc:test","sa","");
System.out.println("Connection established");
}
catch(Exception e)
{
System.out.println("Database not found!");
}
resp.setContentType("text/html");
PrintWriter out=resp.getWriter();
String username=req.getParameter("username").trim();
String pass=req.getParameter("pass").trim();
try
{
PreparedStatement stat=dbcon.prepareStatement(
"select * from UserData where username=? and pass=?");
stat.setString(1,username);
stat.setString(2,pass);
ResultSet result=stat.executeQuery();
if(result.next())
{
out.println("<html><body bgcolor=pink>");
out.println(" Login Successful");
out.println("<br><br>");
//Cookie
boolean cookieFound=false;
Cookie myCookie=null;
Cookie[] cookieSet=req.getCookies();
for(int i=0;i<cookieSet.length;i++)
{
if(cookieSet[i].getName().equals("logincount"))
{
cookieFound=true;
myCookie=cookieSet[i];
}
}
if(cookieFound)
{
int temp=Integer.parseInt(myCookie.getValue());
temp++;
if(temp==5)
{
out.println("Congratulations!!!,You have a gife");
}
out.println("This is the "+temp+" time you have logged on");
myCookie.setValue(String.valueOf(temp));
int age=60*60*24*30;
myCookie.setMaxAge(age);
resp.addCookie(myCookie);
cookieFound=false;
}
else
{
int temp=1;
out.println("This is the first time you have logged on");
myCookie=new Cookie("logincount",String.valueOf(temp));
int age=60*60*24*30;
myCookie.setMaxAge(age);
resp.addCookie(myCookie);
}
//end Cookie
out.println("</body></html>");
}
else
{
out.println("<html><body bgcolor=pink>");
out.println(" Login ERROR");
out.println("<br><br>");
out.println("</body></html>");
}
}
catch(Exception e)
{
e.toString();
}
try
{
dbcon.close();
}
catch(Exception e)
{
System.out.println(e.toString());
}
}
} 
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