Servlet Context Attributes Listeners Project

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package com.cv.servlet.context.listeners; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.log4j.Logger; /**  * @author Chandra Vardhan  *  */ public class ContextParamServlet extends HttpServlet {   private static final Logger LOGGER = Logger.getLogger(ContextParamServlet.class);      public void doGet(HttpServletRequest request, HttpServletResponse response)       throws IOException, ServletException {     LOGGER.info("Entered into doGet(--) of ContextParamServlet class... ");     response.setContentType("text/plain");     PrintWriter printWriter = response.getWriter();     ServletContext context = getServletContext();      Dog dog = (Dog) context.getAttribute("dog");      LOGGER.info("Getting Context attribute 'dog' from ContextParamServlet class... ");      printWriter.print("Dog's name is : " + dog.getName());      LOGGER.info("Removing Context attribute 'dog' from ContextParamServlet class... ");      context.removeAttribute("dog");               }   /**    * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse    *      response)    */   protected void doPost(HttpServletRequest request,       HttpServletResponse response) throws ServletException, IOException {     LOGGER.info("Entered into doPost(--) of ContextParamServlet class... ");     doGet(request, response);   } }

package com.cv.servlet.context.listeners; /**  * @author Chandra Vardhan  *  */ public class Dog {      private String name;   public String getName() {     return name;   }   public void setName(String name) {     this.name = name;   }   public Dog(String name) {     this.name = name;   } }

package com.cv.servlet.context.listeners; import javax.servlet.ServletContextAttributeEvent; import javax.servlet.ServletContextAttributeListener; import org.apache.log4j.Logger; /**  * @author Chandra Vardhan  *  */ public class ServletContextAttributeListenerImpl implements     ServletContextAttributeListener {   private static final Logger LOGGER = Logger       .getLogger(ServletContextAttributeListenerImpl.class);   public void attributeAdded(       ServletContextAttributeEvent servletContextAttributeEvent) {     LOGGER.info("ServletContextAttributeListenerImpl class of attributeAdded(ServletContextAttributeEvent)...");     Dog dog = (Dog) servletContextAttributeEvent.getValue();     LOGGER.info("Value of the context attribute is : " + dog.getName());     LOGGER.info("Checking whether it is stored as context attribute : "         + servletContextAttributeEvent.getServletContext()             .getAttribute("dog"));     dog.setName("Tommy is the second pet name...");     servletContextAttributeEvent.getServletContext().setAttribute("dog",         dog);     }   public void attributeRemoved(       ServletContextAttributeEvent servletContextAttributeEvent) {     LOGGER.info("ServletContextAttributeListenerImpl class of attributeRemoved(ServletContextAttributeEvent)...");     Dog dog = (Dog) servletContextAttributeEvent.getValue();     LOGGER.info("Value of the context attribute is : " + dog.getName());     LOGGER.info("Checking whether it is stored as context attribute : "         + servletContextAttributeEvent.getServletContext()             .getAttribute("dog"));     LOGGER.info("Value of the context attribute is removed... " );   }   public void attributeReplaced(       ServletContextAttributeEvent servletContextAttributeEvent) {     LOGGER.info("ServletContextAttributeListenerImpl class of attributeReplaced(ServletContextAttributeEvent)...");     Dog dog = (Dog) servletContextAttributeEvent.getValue();     LOGGER.info("Value of the context attribute is : " + dog.getName());     /*dog.setName("Bubby is the third pet name...");     servletContextAttributeEvent.getServletContext().setAttribute("dog",         dog);*/     } }

/**  *   */ package com.cv.servlet.context.listeners; import javax.servlet.ServletContext; import javax.servlet.ServletContextEvent; import javax.servlet.ServletContextListener; import org.apache.log4j.Logger; /**  * @author Chandra Vardhan  *  */ public class ServletContextListenerImpl implements ServletContextListener {   private static final Logger LOGGER = Logger       .getLogger(ServletContextListenerImpl.class);   @Override   public void contextDestroyed(ServletContextEvent event) {     LOGGER.info("ServletContextListenerImpl ..ServletContextEvent.. contextDestroyed...");   }   @Override   public void contextInitialized(ServletContextEvent event) {     LOGGER.info("ServletContextListenerImpl class of contextInitialized(ServletContextEvent)...");     ServletContext servletContext = event.getServletContext();     String contextParam = servletContext.getInitParameter("contextParam");     Dog dog = new Dog(contextParam);     LOGGER.info("Value of contextParam is : "+contextParam+" set as context attribute...");     servletContext.setAttribute("dog", dog);   } }

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Context Param</title> </head> <body> <form  method="POST" action="ContextParamServlet">       <br><br>     <center>         <input type="SUBMIT" value="Please Click here">     </center>   </form> </body> </html>

#By default enabling Console appender # Root logger option log4j.rootLogger=INFO, stdout # Redirect log messages to console log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target=System.out log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%-5p [%c]:%L -->> %m%n # Redirect log messages to a log file #log4j.appender.file=org.apache.log4j.RollingFileAppender #log4j.appender.file.File=C:\\servlet-application.log #log4j.appender.file.MaxFileSize=5MB #log4j.appender.file.MaxBackupIndex=10 #log4j.appender.file.layout=org.apache.log4j.PatternLayout #log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <artifactId>ServletContextAttributesListeners</artifactId> <version>1.0</version> <packaging>war</packaging> <properties> <log4j.version>1.2.16</log4j.version> <java.version>1.8</java.version> </properties> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <version>3.3</version> <configuration> <source>${java.version}</source> <target>${java.version}</target> </configuration> </plugin> <plugin> <artifactId>maven-war-plugin</artifactId> <version>2.6</version> <configuration> <warSourceDirectory>WebContent</warSourceDirectory> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> </plugins> </build> <dependencies> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>3.0-alpha-1</version> </dependency> <dependency> <groupId>commons-fileupload</groupId> <artifactId>commons-fileupload</artifactId> <version>1.3.1</version> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>${log4j.version}</version> </dependency> <dependency> <groupId>javax.servlet.jsp</groupId> <artifactId>jsp-api</artifactId> <version>2.0</version> </dependency> <dependency> <groupId>jstl</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>1.1.2</version> </dependency> </dependencies> <groupId>com.cv.servlet.context.listeners</groupId> </project>

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <context-param> <param-name>contextParam</param-name> <param-value>JokeyIsTheFirstPetName</param-value> </context-param> <servlet> <servlet-name>ContextParamServlet</servlet-name> <servlet-class>com.cv.servlet.context.listeners.ContextParamServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ContextParamServlet</servlet-name> <url-pattern>/ContextParamServlet</url-pattern> </servlet-mapping> <listener> <listener-class> com.cv.servlet.context.listeners.ServletContextListenerImpl</listener-class> </listener> <listener> <listener-class>com.cv.servlet.context.listeners.ServletContextAttributeListenerImpl</listener-class> </listener> <welcome-file-list> <welcome-file>input.html</welcome-file> </welcome-file-list> </web-app>