Servlet application for login page

Q. Write a Servlet application for login page, which is check the username and password. If username and password are matched, display welcome message.

Answer:

In this example, we match the username and password from the database.

First create the userlist table

Create table userlist(name varchar2(20), pass varchar2(20));

There are five files in the below program.

i. Index.html
ii. FirstServlet.java
iii. LoginDao.java
iv. WelcomeServlet.java
v. Web.xml

Index.html

<!doctype html>
<html lang="en">
     <head>
          <title>Document</title>
     </head>
     <body>
          <form action="servlet1" method="post">
               <fieldset style="width:20%; background-color:#ccffcc">
                    <h2 align="center">Login Page</h2>
                    <hr>
                    <table>
                    <tr><td>Name</td><td><input type="text" name="username"/></td>
                    <tr><td>Password</td><td><input type="password" name="userpass"/></td></tr>
                    <tr><td></td><td><input type="submit" value="login"/></td></tr>
                    </table>
               </fieldset>
          </form>
     </body>
</html>

FirstServlet.java

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

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

          String n=request.getParameter("username");
          String p=request.getParameter("userpass");
          if(LoginDao.validate(n, p))
          {
               RequestDispatcher rd=request.getRequestDispatcher("servlet2");
               rd.forward(request,response);
          }
          else
          {
               out.print("Sorry username or password error");
               RequestDispatcher rd=request.getRequestDispatcher("index.html");
               rd.include(request,response);
          }
          out.close();
     }
}

LoginDao.java

import java.sql.*;
public class LoginDao
{
     public static boolean validate(String name,String pass)
     {
          boolean status=false;
          try
          {
               Class.forName("oracle.jdbc.driver.OracleDriver");
               Connection con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","local","test");

               PreparedStatement ps=con.prepareStatement(
               "select * from userreg where name=? and pass=?");
               ps.setString(1,name);
               ps.setString(2,pass);
               ResultSet rs=ps.executeQuery();
               status=rs.next();
          }
          catch(Exception e)
          {
               System.out.println(e);
          }
          return status;
     }
}

WelcomeServlet.java

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

public class WelcomeServlet extends HttpServlet
{
     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
     {
          response.setContentType("text/html");
          PrintWriter out = response.getWriter();
          String n=request.getParameter("username");
          out.print("Welcome "+n);
          out.close();
     }
}

web.xml

<web-app>
  <servlet>
    <servlet-name>FirstServlet</servlet-name>
    <servlet-class>FirstServlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>WelcomeServlet</servlet-name>
    <servlet-class>WelcomeServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>FirstServlet</servlet-name>
    <url-pattern>/servlet1</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>WelcomeServlet</servlet-name>
    <url-pattern>/servlet2</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>

</web-app>

Output:

i. Enter username or password

login page

ii. Correct username and password

login page