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Login Servlet

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posted 12 years ago

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Hello Sir,

It's my first project, want to create login servlet for employee.

i have created jsp but not getting the logic to create Servlet for the same.

The jsp code is as follows :

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">

<tr>
    <td height="33"><a href="ZoneWise.jsp"><img src="Untitled-2_19.gif" width="182" height="31" /></a></td>
  </tr>
  </table>
    </td>
  </tr>
  <tr>
    <td><table width="49%" border="0" cellpadding="0" cellspacing="0">
  <tr>
    <th scope="col"><img src="Untitled-2_03.gif" width="182" height="32" /></th>
  </tr>
  <tr>
    <td><img src="Untitled-2_25.gif" width="181" height="26" /></td>
  </tr>
  <tr>
    <td><a href="WaterConservation.jsp"><img src="Untitled-2_29.gif" width="179" height="28" /></a></td>
  </tr>
  <tr>
    <td><img src="Untitled-2_31.gif" width="180" height="26" /></td>
  </tr>
  <tr>
    <td><a href="WaterSupply.jsp"><img src="Untitled-2_35.gif" width="180" height="28" /></a></td>
  </tr>
</table>
</td>
  </tr>
  <tr>
    <td height="128"><table width="61%" border="0" cellpadding="0" cellspacing="0">
  <tr>
    <th scope="col"><img src="Untitled-2_07.gif" width="181" height="35" /></th>
  </tr>
  <tr>
    <td><img src="Untitled-2_32.gif" width="184" height="30" /></td>
  </tr>
  <tr>
    <td><img src="Untitled-2_37.gif" width="183" height="29" /></td>
  </tr>
  <tr>
     <td><a href="RegisterComplaint.jsp"><img src="Untitled-2_41.gif" width="183" height="29" /></a></td>
  </tr>
 </table>
 </td>
</tr>
</table>
    
</td>
<td width="71%" align="center" valign="middle"><table width="235" height="136" border="0" background="adminlog_03.gif" >
  <tr>
    <th scope="col" colspan="2"><font size="+2"><b>Login</b></font></th>
    </tr>
  <tr>
      <td width="102" align="center" valign="bottom"><font size="+1">Employee-ID</font></td><td><input type="text" name="empid"></td>
   </tr>
  <tr>
      <td width="130" align="center" valign="bottom"><font size="+1">Password</font></td><td><input type="password" name="password"</td>
  </tr>
    <tr><td colspan="2" >        <input type="submit" value="Sign-in" name="signin">    
                            <input type="reset" value="Cancel" name="cancel"></td></tr>
</table></td>
  </tr>
  <tr>
    <td colspan="2"><img src="footer_02.gif" width="762" height="26" /></td>
  </tr>
</table>

</body>
    </body>
</html>
[code=java]

Habeeb Shaikh

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posted 12 years ago

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Hi mohini,
What you want to say exactly.Do you want to create a servlet ? how to use it? or anything else?

Mohini Dhanaskar

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posted 12 years ago

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i want to create a login servlet for the employee.

Tim Moores

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posted 12 years ago

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What, exactly, should this servlet do? No sense thinking about details (or even code) unless and until the requirements are clear.

Mohini Dhanaskar

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posted 12 years ago

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Sorry Sir for inconvenience,

There is a jsp called employee login in which the employee has to enter empid and password.

which has been check from database table EmpRegistration.

If the employee is registered and valid ,EmailFormat jsp will appear or else LoginError.jsp will appear.

hope this has given you some idea.

Habeeb Shaikh

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posted 12 years ago

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hi mohini, do not called me as sir,

1. Create a class LoginServlet.
2. Create 2 setter and getter method for empname and password.
3. In getter method you can write your any validation code like emp does not exit if it is not in database or any your simple arraylist.
4. Import LoginServlet into your .jsp class
5 Set value attribute of empname text field by using loginServlet.getEmpname()

I hope you understand it.let me know if any difficulty.

Mohini Dhanaskar

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posted 12 years ago

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thank you, i will try and let you know.

Tim Moores

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Habeeb Shaikh wrote:
1. Create a class LoginServlet.
2. Create 2 setter and getter method for empname and password.
3. In getter method you can write your any validation code like emp does not exit if it is not in database or any your simple arraylist.
4. Import LoginServlet into your .jsp class
5 Set value attribute of empname text field by using loginServlet.getEmpname()

A servlet is a servlet, not a backing (or model) bean. It does not need getters and setters, and it should definitely not be used in a JSP page. The basic steps of the servlet code are: retrieve username and password from the request, use them to check for validity against the DB, and depending on that redirect to either of the JSP pages. Which of these steps are you having difficulties with?

Also note that you need to fix your HTML - while there are several input fields, there is no actual <form ...> ... </form> tag. Without that there'S no way to specify the URL of the servlet that the form should be submitted to, or that the HTTP method to be used is a POST.

Swastik Dey

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posted 12 years ago

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Habeeb Shaikh wrote:hi mohini, do not called me as sir,

1. Create a class LoginServlet.
2. Create 2 setter and getter method for empname and password.
3. In getter method you can write your any validation code like emp does not exit if it is not in database or any your simple arraylist.
4. Import LoginServlet into your .jsp class
5 Set value attribute of empname text field by using loginServlet.getEmpname()

I hope you understand it.let me know if any difficulty.

Why should a servlet have a setter, getter methods. Servlet is a controller. What is the need of importing a servlet in jsp? You should never embed java code in jsp it's a very old practice and not at all recommended these days, use el/jstl/custom tags etc. Your process flow should be like this

1. Create a login page which has two textboxes to enter user id and password
2. The submit action of this page is mapped to a servlet
3. Servlet retrieves the value of those two boxes using getParameter method of request object.
4. You do the required validation in the servlet or using some helper classes.
5. Based on the validity of user credentials you redirect the user to the specific jsp/html page.

Swastik

Mohini Dhanaskar

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posted 12 years ago

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i have tried sir as you said,

but i am getting an error as follow :

and the servlet code is as folllow:

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 *
 * @author Administrator
 */

public class EmpLoginServlet extends HttpServlet {
    private String empid;

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        try {
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();
            HttpSession session = request.getSession();
            String empid = request.getParameter("empid");
            String password = request.getParameter("password");
            Connection connection = DatabaseConnection.getConnection();
            System.out.println("Database Connected");

//Using PreparedStatement Class

PreparedStatement ps = connection.prepareStatement("select empid,password from EmpRegistration where empid=? and password=?");

ps.setString(1, empid);
            ps.setString(2, password);

ResultSet rs = ps.executeQuery();

String submit=request.getParameter("submit");
            System.out.println("submit= " + submit);

if(submit.equals("SUBMIT"))
            {

if (rs.next()) {
                System.out.println("Valid User");
                session.setAttribute("empid", empid);
                session.setAttribute("password", password);
                response.sendRedirect("EmailFormatServlet.jsp");

} else {
                System.out.println("Invalid User");
                response.sendRedirect("LoginErrorForm.jsp");

}
            }

} catch (SQLException ex) {
            Logger.getLogger(NewServlet.class.getName()).log(Level.SEVERE, null, ex);
        }

}

Swastik Dey

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posted 12 years ago

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Mohini,

What code do you have in line#48 EmpLoginServlet?

Swastik

Mohini Dhanaskar

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posted 12 years ago

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Nothing Sir.

Actually i didn't understand what should i write there,or should i use that if block or not.

Swastik Dey

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posted 12 years ago

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It can't be nothing, look at the exception you are getting

java.lang.NullPointerException
EmpLoginServlet.processRequest(EmpLoginServlet.java:48)

and I don't think you need the following check

unless you have more than one submit button in the same page with different values.

Swastik

Mohini Dhanaskar

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posted 12 years ago

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Ok, Sir

I will remove these lines from code.

Tim Moores

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It looks like you're storing passwords in cleartext in the DB; that's a huge No-No for security reasons!

Kunal Lakhani

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posted 12 years ago

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Mohini Dhanaskar , its better to separate Persistence logic from servlet. Why don't you go for MVC architecture?

kunal

Mohini Dhanaskar

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posted 12 years ago

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ok,

Sir,then what should i do to resolved this?

Swastik Dey

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posted 12 years ago

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Tim's and Kunal's suggestion is excellent. But what happened after removing that if check? Did it still not work?

Swastik

Prashant Chindhade

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posted 12 years ago

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first try simple application like this.

Login.jsp file.

this is bean class which is used to hold the data. it is also called model class.
Employee.java

now write servlet. like this.
LoginServlet.java

try this.

Mohini Dhanaskar

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Swastik Sir, i removed that lines and run it ..it is displaying LoginError.jsp page.

But Sir,while running Employee Login page,there is no action after clicking signin button.

Not getting,where i am wrong.

Tim Moores

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Time to do some debugging: Is the page being submitted, meaning: is the servlet being invoked? If so, what are the values of the parameters?

Be aware that we do not see your code, so we have no idea what might or might not be happening.

Swastik Dey

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posted 12 years ago

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prashant,

You should never compare a String object like this

it should have been (use methods of String class)

Mohini,

What you are saying is little confusing. You said that it's displaying the login error page, that means it's being redirected from the servlet, right, and again you are saying nothing happens if you click on the submit button.

Swastik

Prashant Chindhade

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posted 12 years ago

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Swastik Dey wrote:prashant,

You should never compare a String object like this

if(name != "")

it should have been (use methods of String class)

if(!"".equals(name))

Mohini,

What you are saying is little confusing. You said that it's displaying the login error page, that means it's being redirected from the servlet, right, and again you are saying nothing happens if you click on the submit button.

ya thanks for that. i will follow this now on.

Mohini Dhanaskar

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posted 12 years ago

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Swastik Sir,i mean to say that

if i run only that servlet alone it is displaying LoginError.jsp.

Bu when i run the EmployeeLogin jsp that time after clicking signin(submit) button there is
no respond.

Swastik Dey

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Mohini,

By this what I understand is, when you are hitting the mapped url of the servlet in the browser you are getting the login error page, that may be possible because it may not be getting the query parameter values. As far as the second problem is concerned, probably we need to see the code of your login page, i.e form action, and the web.xml file to know whether the servlet mapping is correct or not.

Swastik

Mohini Dhanaskar

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Yuppiii,, my servlet is running properly.

thank you Habeeb Sir, Kunal Sir, Prashant Sir..

and Special thanks to Tim Sir and Swastik Sir..

Thanks a lot.

Swastik Dey

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posted 12 years ago

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You are most welcome Mohini.

Swastik

Habeeb Shaikh

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Your are welcome mohini...

Tim Holloway

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Not to spoil the party, but the technical term for web applications with Login Servlets in them is "hacked", "pwned" or "exploited". I really wish that J2EE books wouldn't use Login Servlets as demonstrators. Java has a much more secure way of doing logins that doesn't require any user-written code at all.

Experience keeps a dear School, but Fools will learn in no other.
---
Benjamin Franklin - Postal official and Weather observer

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