Servlets : Authentication Filter

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Servlets : Authentication Filter

AuthenticationFilterDemo Project Dir Structure

Servlets : Authentication Filter

AuthenticationFilter.java

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class AuthenticationFilter implements Filter
{

 public void init(FilterConfig config) throws ServletException
 {
  System.out
          .println("------------------------------------------------------");
  System.out.println(" init method is called in "
          + this.getClass().getName());
  System.out
          .println("------------------------------------------------------");
 }

 public void doFilter(ServletRequest request, ServletResponse response,
         FilterChain chain) throws IOException, ServletException
 {

  System.out.println(" doFilter method is called in "
          + this.getClass().getName() + "\n\n");

  PrintWriter out = response.getWriter();

  String username = request.getParameter("username");
  String password = request.getParameter("password");
  if (username.equals("admin") && password.equals("admin"))
  {
   // sends request to next resource
   chain.doFilter(request, response);
  }
  else
  {
   out.print("username or password is not correct!");

  }
 }

 public void destroy()
 {
  // add code to release any resource
  System.out
          .println("------------------------------------------------------");
  System.out.println(" destroy method is called in "
          + this.getClass().getName());
  System.out
          .println("------------------------------------------------------");
 }
}

HelloServlet.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 HelloServlet extends HttpServlet
{
 private static final long serialVersionUID = 1L;

 public void init() throws ServletException
 {
  System.out
          .println("------------------------------------------------------");
  System.out.println(" Init method is called in "
          + this.getClass().getName());
  System.out
          .println("------------------------------------------------------");
 }

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

  System.out.println(" doGet method is called in "
          + this.getClass().getName() + "\n\n");
  System.out
          .println("------------------------------------------------------");

  response.setContentType("text/html");
  PrintWriter out = response.getWriter();

  out.print("<br>welcome to helloservlet<br>");

 }

 public void destroy()
 {
  System.out
          .println("------------------------------------------------------");
  System.out.println(" destroy method is called in "
          + this.getClass().getName());
  System.out
          .println("------------------------------------------------------");
 }

}

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
 metadata-complete="true" version="3.0">
 <display-name>AuthenticationFilterDemo</display-name>
 <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>
 <servlet>
  <servlet-name>HelloServlet</servlet-name>
  <servlet-class>HelloServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>HelloServlet</servlet-name>
  <url-pattern>/hello</url-pattern>
 </servlet-mapping>
 <filter>
  <filter-name>AuthFilter</filter-name>
  <filter-class>AuthenticationFilter</filter-class>
 </filter>
 <filter-mapping>
  <filter-name>AuthFilter</filter-name>
  <url-pattern>/hello</url-pattern>
 </filter-mapping>
</web-app>

index.html

<html lang="en">
<head>
<meta charset="UTF-8">
<title>AuthenticationFilter Demo</title>
</head>
<body>
 <form action="hello" method="GET">
  
  UserName :  <input type="text" name="username" /><br /> 
  
  Password :&nbsp; &nbsp; <input type="password" name="password" /><br /> 
   
  <input type="submit" value="login" />
  
 </form>
</body>
</html>

Environment Used 

JDK version :1.6.0_30
Tomcat version : 7.0.50

To Download AuthenticationFilterDemoApp Project Click the below link
https://sites.google.com/site/javaee4321/servlets/AuthenticationFilterDemoApp.zip?attredirects=0&d=1

See also:

Servlets Tutorial

All Design Patterns Links