Login Form Using Servlets and Jsp and Dao

This is for UserLogin Form.How to check user Login form using MVC2 architecture. Here Jsp acting as a View Component and DAO act as a Model component and Servlet act as a Controller. 

View Component: 

This is mainly used for presentation purpose.

Model Component:

This is mainly used for ReUseble Component.This Model Componet is directly interact with database server and extra methods.

Controller:

This mainly used for creating a javabean object and call the method and dispatching the servlet to another resource.



Step1: create a login form name login.jsp

step2:develop a Dao and name UserDAO.java

step3: develop a servletclass name LoginServlet.java

step4: if usernme and password is valid open the new page name userLogged.jsp

step5: if username and password is InValid open the new page name invalidLogin.jsp


login.jsp


<form action="LoginServlet">

            Please enter your username        
            <input type="text" name="un"/><br>       
       
            Please enter your password
            <input type="text" name="pw"/>
           
            <input type="submit" value="submit">           
       
        </form>

UserDAO.java

 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;
   
      }   
   }

LoginServlet.java

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.java
 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;
    }   
}

ConnectionManger.java


 */
package a.b;

import java.sql.Connection;
import java.sql.DriverManager;

/**
 *
 * @author user
 */
public class ConnectionManager {
   
    public static Connection get(){
        Connection con=null; 
         try{
           
        Class.forName("com.mysql.jdbc.Driver");
   con=(Connection) DriverManager.getConnection("jdbc:mysql://localhost/ashok","root","");
    
       
    }catch(Exception  e){
       
    }
   return con;
}
}