SERVLET3.0 Learning Summary (iv)--using annotation callout listener (Listener)

SERVLET3.0 Learning Summary (iv)--using annotation callout listener (Listener)

Servlet3.0 provides @weblistener annotations to define a class that implements a specific listener interface as a listener , so that when we use the listener in a web app, we no longer need to configure the listener's descriptive information in the. xml file.

Let's create a listener and experience using the @weblistener annotation callout listener as follows:

　　

The code for the listener is as follows:

1 package Me.gacl.web.listener; 2  3 import javax.servlet.ServletContextEvent; 4 import javax.servlet.ServletContextListener; 5 import Javax.servlet.annotation.WebListener; 6  7/** 8  * Using @weblistener annotations will implement the Myservletcontextlistener labeled Servletcontextlistener interface as Listener 9  */10 @ WebListener11 public class Myservletcontextlistener implements Servletcontextlistener {     @Override14     public void contextdestroyed (Servletcontextevent sce) {         System.out.println ("Servletcontex destroyed");     }17 18     @Override19 public     void contextinitialized (Servletcontextevent sce) {         System.out.println (" Servletcontex initialization "),         System.out.println (Sce.getservletcontext (). Getserverinfo ());     

The listener is initialized when the Web app starts, as shown in:

　　

With @weblistener annotations, our web. XML does not have to be configured

1 <?xml version= "1.0" encoding= "UTF-8"?> 2 <web-app version= "3.0"  3     xmlns= "http://java.sun.com/xml/ Ns/javaee "  4     xmlns:xsi=" Http://www.w3.org/2001/XMLSchema-instance "  5     xsi:schemalocation=" http ://java.sun.com/xml/ns/javaee  6     http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd "> 7   < Display-name></display-name>     8   <welcome-file-list> 9     <welcome-file>index.jsp </welcome-file>10   </welcome-file-list>11 </web-app>

The advent of the SERVLET3.0 specification allows us to develop servlet, filter, and listener programs that implement zero configuration in Web. Xml.

SERVLET3.0 Learning Summary (iv)--using annotation callout listener (Listener)