// File: LoginHandler.java
// This servlet checks the username and password for validity.
// If the client fails the check, they are told that access is denied.
// If the client passes, that fact is recorded in their session object
// and they are immediately redirected to the original target (obtained
// from the Session object).
import java.io.*;
import java.util.*;
import java.net.URL;
import javax.servlet.*;
import javax.servlet.http.*;
public class LoginHandler extends HttpServlet {
private Properties passwords;
private String passwordFile;
public void init(ServletConfig config)
throws ServletException {
super.init(config);
try {
// config.getInitParameter is specified within the servlet's
// spec in the web.xml file
passwords = new Properties();
passwords.load(getServletContext().
getResourceAsStream("/WEB-INF/passwords"));
}
catch(IOException ioe) {
}
catch(Exception excpt) {
}
}
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
// Get the user's name and password
String name = req.getParameter("name");
String passwd = req.getParameter("passwd");
// Check the name and password for validity
if (!allowUser(name, passwd)) {
out.println("Access Denied");
out.println("Your login and password are invalid.
");
out.println("Login");
}
else {
out.println("Welcome "+name+"
");
// Valid login. Make a note in the session object.
HttpSession session = req.getSession(true);
session.putValue("logon.isDone", name); // just a marker object
// Try redirecting the client to the page he first tried to access
try {
String target = (String) session.getValue("login.target");
if (target != null)
res.sendRedirect(target);
return;
}
catch (Exception ignored) {
out.println("Redirect failed!");
}
// Couldn't redirect to the target. Redirect to the site's home page.
res.sendRedirect(req.getScheme() + "://" +
req.getServerName() + ":" + req.getServerPort());
}
out.println("");
}
protected boolean allowUser(String user, String passwd) {
String realPassword = passwords.getProperty(user);
if (realPassword != null && realPassword.equals(passwd))
return true; // trust everyone
return(false);
}
}