java code for Login Servlets

/*

Java Programming with Oracle JDBC
by Donald Bales
ISBN: 059600088X
Publisher: O'Reilly

*/



import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class Login extends HttpServlet {

public void init(ServletConfig config) throws ServletException {
super.init(config);
try {
// load the driver
Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
} catch (ClassNotFoundException e) {
throw new UnavailableException(
"Login init() ClassNotFoundException: " + e.getMessage());
} catch (IllegalAccessException e) {
throw new UnavailableException(
"Login init() IllegalAccessException: " + e.getMessage());
} catch (InstantiationException e) {
throw new UnavailableException(
"Login init() InstantiationException: " + e.getMessage());
}
}

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

response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println("");
out.println("");
out.println("");

HttpSession session = request.getSession();
Connection connection = (Connection) session.getAttribute("connection");
if (connection == null) {
String userName = request.getParameter("username");
String password = request.getParameter("password");
if (userName == null || password == null) {
// prompt the user for her username and password
out.println("

");
out.println("Please specify the following to log in:

");
out.println("Username: + "name=\"username\" size=\"30\">

");
out.println("Password: + "name=\"password\" size=\"30\">

");
out.println("");
out.println("

");
} else {
// create the connection
try {
connection = DriverManager.getConnection(
"jdbc:oracle:thin:@dssw2k01:1521:orcl", userName,
password);
} catch (SQLException e) {
out.println("Login doGet() " + e.getMessage());
}
if (connection != null) {
// store the connection
session.setAttribute("connection", connection);
response.sendRedirect("Login");
return;
}
}
} else {
String logout = request.getParameter("logout");
if (logout == null) {
// test the connection
Statement statement = null;
ResultSet resultSet = null;
String userName = null;
try {
statement = connection.createStatement();
resultSet = statement
.executeQuery("select initcap(user) from sys.dual");
if (resultSet.next())
userName = resultSet.getString(1);
} catch (SQLException e) {
out.println("Login doGet() SQLException: " + e.getMessage()
+ "

");
} finally {
if (resultSet != null)
try {
resultSet.close();
} catch (SQLException ignore) {
}
if (statement != null)
try {
statement.close();
} catch (SQLException ignore) {
}
}
out.println("Hello " + userName + "!

");
out.println("Your session ID is " + session.getId() + "

");
out
.println("It was created on "
+ new java.util.Date(session.getCreationTime())
+ "

");
out.println("It was last accessed on "
+ new java.util.Date(session.getLastAccessedTime())
+ "

");
out.println("

");
out.println(" + "value=\"Logout\">");
out.println("

");
} else {
// close the connection and remove it from the session
try {
connection.close();
} catch (SQLException ignore) {
}
session.removeAttribute("connection");
out.println("You have been logged out.");
}
}
out.println("");
out.println("");
}

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