Servlets : ServletRequestAttributeListener Demo

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ServletRequestAttributeListenerDemo Project Dir Structure

ServletRequestAttributeTestServlet.java

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletRequestAttributeTestServlet 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
    {
        response.setContentType("text/html");

        sleep();
        
        request.setAttribute("CompanyName", "Wipro");

        sleep();

        request.setAttribute("CompanyName", "Infosys");

        sleep();

        request.removeAttribute("CompanyName");

    }

    private void sleep()
    {
        try
        {
            Thread.sleep(10000);
        }
        catch( InterruptedException e )
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

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

}

MyServletRequestAttributeListener.java

import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;

public class MyServletRequestAttributeListener implements
        ServletRequestAttributeListener
{

    @Override
    public void attributeAdded(
            ServletRequestAttributeEvent servletRequestAttributeEvent )
    {
        System.out.println("\n###################################\n");

        System.out.println("attributeAdded method has been called in "
                + this.getClass().getName());

        System.out.println("Newly added Attribute Name ="
                + servletRequestAttributeEvent.getName() + ",value = "
                + servletRequestAttributeEvent.getValue());

        System.out.println("\n#####################################\n");

        /*
         * if particular Attribute is added, based on that if you want to
         * perform any operation then you can do it here.
         */

    }

    @Override
    public void attributeRemoved(
            ServletRequestAttributeEvent servletRequestAttributeEvent )
    {
        System.out.println("\n###################################\n");

        System.out.println("attributeRemoved method has been called "
                + this.getClass().getName());

        System.out.println("Removed Attribute Name ="
                + servletRequestAttributeEvent.getName() + ",value = "
                + servletRequestAttributeEvent.getValue());

        System.out.println("\n###################################\n");

        /*
         * if particular Attribute is Removed, based on that if you want to
         * perform any operation then you can do it here.
         */

    }

    @Override
    public void attributeReplaced(
            ServletRequestAttributeEvent servletRequestAttributeEvent )
    {
        System.out.println("\n###################################\n");

        System.out.println("attributeReplaced method has been called "
                + this.getClass().getName());

        System.out.println("Replaced Attribute Name ="
                + servletRequestAttributeEvent.getName() + ",value = "
                + servletRequestAttributeEvent.getValue());

        System.out.println("\n###################################\n");

        /*
         * if particular Attribute is Replaced, based on that if you want to
         * perform any operation then you can do it here.
         */

    }

}

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>ServletRequestAttributeListenerDemo</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>ServletRequestAttributeTestServlet</servlet-name>
        <servlet-class>ServletRequestAttributeTestServlet</servlet-class>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>ServletRequestAttributeTestServlet</servlet-name>
        <url-pattern>/listenerTest</url-pattern>
    </servlet-mapping>

    <listener>
        <listener-class>MyServletRequestAttributeListener</listener-class>
    </listener>


</web-app>

index.html

<html>
<body>
    <a href="listenerTest">listenerTest</a>
</body>
</html>

Environment Used 

JDK version :1.7.0_51
Tomcat version : 7.0.50 

To Download ServletRequestAttributeListenerDemoApp Project Click the below link

https://sites.google.com/site/javaee4321/servlets/ServletRequestAttributeListenerDemoApp.zip?attredirects=0&d=1

See also:

Servlets Tutorial

All Design Patterns Links