To show the Error message at the login.jsp page using servlet

[Shivoham Pandey]

Hi folks
I am doing a project for which i need to display the error message to the same login.jsp page using servlet.Error messages should be of there types:
For invalid username:invalid user name
For invalid password:Invalid password
For Invalid username or password:user details are not found in database
I am doing these validation against MS-Access Database.
I have written a code which is giving only one type of error:
Thats :For Invalid username or password:user details are not found in database.
Please help me out.Thanks in Advance

package com.Demo.Servlet_EmployeeProject;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class LoginEmployee extends HttpServlet{ 
 
   public void doPost(HttpServletRequest request, HttpServletResponse response)
                                   throws ServletException,IOException{
      //response.setContentType("text/html");
     // PrintWriter out = response.getWriter();

      System.out.println("MySQL Connect Example.");
      Connection conn = null;
      String url = "jdbc:odbc:Employee";
      String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
      
       String username=request.getParameter("username");
       String userpass=request.getParameter("password");
       String strQuery= ""; 
      Statement st=null;
      ResultSet rs=null;
      HttpSession session = request.getSession(false);
     
      try {
        Class.forName(driver).newInstance();
        conn = DriverManager.getConnection(url);
          System.out.println(userpass);
           strQuery="select * from Employee"+" where uid="+username+" and  password='"+userpass+"'";
           System.out.println(strQuery);
          // PreparedStatement ps = conn.prepareStatement("select * from Employee"+" where uid='"+username+"' and  password='"+userpass+"'");
        
          // rs = ps.executeQuery();

          st = conn.createStatement();
          rs = st.executeQuery(strQuery);
         
          int count=0;
          while(rs.next())
          {
            session.setAttribute("username",rs.getString(1));
            session.setAttribute("password",rs.getString(2));
            session.setAttribute("aid",rs.getString(3));
            session.setAttribute("fname",rs.getString(4));
            session.setAttribute("lname",rs.getString(5)); 
            session.setAttribute("display",rs.getString(6));
            session.setAttribute("design",rs.getString(7));
            session.setAttribute("email",rs.getString(8));
            session.setAttribute("address",rs.getString(9));
            
            count++;
          }

                    if(count>0)
          {
            
           // response.sendRedirect("welcome.jsp");		
            RequestDispatcher dispatcher = request.getRequestDispatcher("/welcome.jsp");
            dispatcher.forward( request, response);
          }
          else
         {
        	  
        	  request.setAttribute("errorMessage", "Invalid username or password"); 
              RequestDispatcher dispatcher = request.getRequestDispatcher("/LoginPage.jsp");
              dispatcher.forward( request, response);
                     //  response.sendRedirect("LoginPage.jsp");
          }
          
        System.out.println("Connected to the database");       
        
        conn.close();
        System.out.println("Disconnected from database");
      } catch (Exception e ) {
      e.printStackTrace();
      
      }finally{
    	  if ((username==""||username==null)&&(userpass==""||userpass==null))
			  session.setAttribute("message", "Please Re-login"); 
		      RequestDispatcher dispatcher = request.getRequestDispatcher("/LoginPage.jsp");
		      dispatcher.forward( request, response);
    	  }
  }
}
    

This code is working fine for the third type of Error.
I have also written a code to display all the three errors.But it is not working

   package com.Demo.Servlet02;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

public class LoginServlet01 extends HttpServlet{ 
 
   public void doPost(HttpServletRequest request, HttpServletResponse response)
                                   throws ServletException,IOException{
      //response.setContentType("text/html");
     // PrintWriter out = response.getWriter();

      System.out.println("MySQL Connect Example.");
      Connection conn = null;
      String url = "jdbc:odbc:Employee";
      String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
       String username=request.getParameter("username");
       String userpass=request.getParameter("password");
       String strQuery= "";
       String sqid="";
       String sqpass="";
      Statement st=null;
      Statement st1=null;
      ResultSet rs=null;
      ResultSet rs1=null;
     
      HttpSession session = request.getSession(true);

      try {
        Class.forName(driver).newInstance();
        conn = DriverManager.getConnection(url);
       
        sqid="select uid,password from Employee"+"where uid='"+username+"'";
        
        System.out.println( sqid);
        System.out.println( sqid);
        st1 = conn.createStatement();
        rs = st.executeQuery(sqid);
        rs1=st.executeQuery(sqpass);
        if(username!=rs.getString(1) && userpass.equals(rs1.getString(2))){
        	request.setAttribute("errorMessage", "Invalid username"); 
            RequestDispatcher dispatcher = request.getRequestDispatcher("/LoginPage.jsp");
            dispatcher.forward( request, response);
        }else if(username.equals(rs.getString(1)) && userpass!=rs.getString(2)){
	request.setAttribute("errorMessage", "Invalid password"); 
    RequestDispatcher dispatcher = request.getRequestDispatcher("/LoginPage.jsp");
    dispatcher.forward( request, response);
}else{
          System.out.println(userpass);
           strQuery="select * from Employee"+" where uid='"+username+"' and  password='"+userpass+"'";
           System.out.println(strQuery);
          // PreparedStatement ps = conn.prepareStatement("select * from Employee"+" where uid='"+username+"' and  password='"+userpass+"'");
        
          // rs = ps.executeQuery();

          st = conn.createStatement();
          rs = st.executeQuery(strQuery);
          int count=0;
          while(rs.next())
          {
            
            session.setAttribute("username1",rs.getString(3));
            session.setAttribute("username2",rs.getString(4));
            session.setAttribute("username3",rs.getString(5)); 
            session.setAttribute("username4",rs.getString(6));
            session.setAttribute("username5",rs.getString(7));
            session.setAttribute("username6",rs.getString(8));
            session.setAttribute("username7",rs.getString(9));
            
            count++;
          }

                    if(count>0)
          {
            
           // response.sendRedirect("welcome.jsp");		
            RequestDispatcher dispatcher = request.getRequestDispatcher("/welcome.jsp");
            dispatcher.forward( request, response);
          }
          else
         {
        	  
        	  request.setAttribute("errorMessage", "Invalid username or password"); 
              RequestDispatcher dispatcher = request.getRequestDispatcher("/LoginPage.jsp");
              dispatcher.forward( request, response);
                     //  response.sendRedirect("LoginPage.jsp");
          }
      
}
        
        System.out.println("Connected to the database");       
        
        conn.close();
        System.out.println("Disconnected from database");
      } catch (Exception e) {
      e.printStackTrace();
      }
  }
}  

.

[Seetharaman Venkatasamy]

Welcome to Javaranch

your logic[the way of querying the DB] is false. check the DB for username,if it is not in DB,then show first error message else go for password checking..and etc... go ahead.

but really what is the use of displaying these many errors ?