How does this example work even if no oracle to be used and only access is available?

How does this example work even if no oracle to be used and only access is available?

CONNECTION CLASS

package ExamplePackage;

import java.sql.*; import java.util.*;

public class ConnectionManager {

  static Connection con;
  static String url;

  public static Connection getConnection()
  {

     try
     {

        Class.forName("oracle.jdbc.driver.OracleDriver");
        System.out.println(" Defing the URL");

         String url= "jdbc:oracle:thin:@172.24.137.30:1521:ORA10G";
        // assuming "DataSource" is your DataSource name

       // Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

        try
        {   


            System.out.println(" Defing the username");
            String username= ""; 
            System.out.println(" Defing the password");
            String password= "";
            System.out.println(" Defing the connection");
            con = DriverManager.getConnection(url,username,password); 
            System.out.println(" connection done" +con);





        }

        catch (SQLException ex)
        {
           ex.printStackTrace();
        }
     }

     catch(ClassNotFoundException e)
     {
        System.out.println(e);
     }

  return con;

} }

LOGIN SERVLET

package ExamplePackage;

import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;

/** * Servlet implementation class LoginServlet */ public class LoginServlet extends HttpServlet {

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

try {

 UserBean user = new UserBean();
 user.setUserName(request.getParameter("un"));
 user.setPassword(request.getParameter("pw"));

 user = UserDAO.login(user);

 if (user.isValid())
 {

      HttpSession session = request.getSession(true);       
      session.setAttribute("currentSessionUser",user); 
      response.sendRedirect("userLogged.jsp"); //logged-in page             
 }

 else 
      response.sendRedirect("invalidLogin.jsp"); //error page

}

catch (Throwable theException)
{ System.out.println(theException); } } }

USERBEAN

package ExamplePackage;

public class UserBean {

  private String username;
  private String password;
  private String firstName;
  private String lastName;
  public boolean valid;


  public String getFirstName() {
     return firstName;
}

  public void setFirstName(String newFirstName) {
     firstName = newFirstName;
}


  public String getLastName() {
     return lastName;
        }

  public void setLastName(String newLastName) {
     lastName = newLastName;
        }


  public String getPassword() {
     return password;
}

  public void setPassword(String newPassword) {
     password = newPassword;
}


  public String getUsername() {
     return username;
        }

  public void setUserName(String newUsername) {
     username = newUsername;
        }


  public boolean isValid() {
     return valid;
}

  public void setValid(boolean newValid) {
     valid = newValid;
}

}

USERDAO package ExamplePackage;

import java.text.*; import java.util.*; import java.sql.*;

public class UserDAO
{ static Connection currentCon = null; static ResultSet rs = null;

  public static UserBean login(UserBean bean) {

     //preparing some objects for connection 
     Statement stmt = null;    

     String username = bean.getUsername();    
     String password = bean.getPassword();   

     String searchQuery =
           "select * from users where username='"
                    + username
                    + "' AND password='"
                    + password
                    + "'";

  // "System.out.println" prints in the console; Normally used to trace the process
  System.out.println("Your user name is " + username);          
  System.out.println("Your password is " + password);
  System.out.println("Query: "+searchQuery);

  try 
  {
     //connect to DB 
     currentCon = ConnectionManager.getConnection();
     stmt=currentCon.createStatement();
     rs = stmt.executeQuery(searchQuery);           
     boolean more = rs.next();

     // if user does not exist set the isValid variable to false
     if (!more) 
     {
        System.out.println("Sorry, you are not a registered user! Please sign up first");
        bean.setValid(false);
     } 

     //if user exists set the isValid variable to true
     else if (more) 
     {
        String firstName = rs.getString("firstname");
        String lastName = rs.getString("lastname");

        System.out.println("Welcome " + firstName);
        bean.setFirstName(firstName);
        bean.setLastName(lastName);
        bean.setValid(true);
     }
  } 

  catch (Exception ex) 
  {
     System.out.println("Log In failed: An Exception has occurred! " + ex);
  } 

  //some exception handling
  finally 
  {
     if (rs != null)    {
        try {
           rs.close();
        } catch (Exception e) {}
           rs = null;
        }

     if (stmt != null) {
        try {
           stmt.close();
        } catch (Exception e) {}
           stmt = null;
        }

     if (currentCon != null) {
        try {
           currentCon.close();
        } catch (Exception e) {
        }

        currentCon = null;
     }
  }

return bean;

  }

}

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