Servlets : ServletContextAttributeListener Demo

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ServletContextAttributeListenerDemo Project Dir Structure

ServletContextAttributeTestServlet.java

import java.io.IOException;

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

public class ServletContextAttributeTestServlet 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");
        
        ServletContext servletContext = getServletContext();

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

        sleep();

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

        sleep();

        servletContext.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("-----------------------------------------");
    }

}

MyServletContextAttributeListener.java

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;

public class MyServletContextAttributeListener implements
        ServletContextAttributeListener
{

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

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

        System.out.println("Newly added Attribute Name ="
                + servletContextAttributeEvent.getName() + ",value = "
                + servletContextAttributeEvent.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(
            ServletContextAttributeEvent servletContextAttributeEvent )
    {
        System.out.println("\n###################################\n");

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

        System.out.println("Removed Attribute Name ="
                + servletContextAttributeEvent.getName() + ",value = "
                + servletContextAttributeEvent.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(
            ServletContextAttributeEvent servletContextAttributeEvent )
    {
        System.out.println("\n###################################\n");

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

        System.out.println("Replaced Attribute Name ="
                + servletContextAttributeEvent.getName() + ",value = "
                + servletContextAttributeEvent.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>ServletContextAttributeListenerDemo</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>ServletContextAttributeTestServlet</servlet-name>
        <servlet-class>ServletContextAttributeTestServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>ServletContextAttributeTestServlet</servlet-name>
        <url-pattern>/listenerTest</url-pattern>
    </servlet-mapping>

    <listener>
        <listener-class>MyServletContextAttributeListener</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 ServletContextAttributeListenerDemoApp Project Click the below link

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

See also:

Servlets Tutorial

All Design Patterns Links