JSP 監聽器總結

概述

https://blog.csdn.net/u011024652/article/details/52293932

https://blog.csdn.net/qq_37651267/article/details/90962152

監聽器作用：

監聽器是Servlet規範中定義的一種特殊類，用於監聽ServletContext、HttpSession和ServletRequest等域對象的創建和銷燬事件，它還可以監聽域對象的屬性發生修改的事件，可以在事件發生前或者發生後做一些必要的處理。

 

IDEA默認創建的監聽器代碼：

它使用了ServletContextListener,HttpSessionListener, HttpSessionAttributeListener 三個監聽器接口

​

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import javax.servlet.http.HttpSessionBindingEvent;

@WebListener()  
public class Listener implements ServletContextListener,
        HttpSessionListener, HttpSessionAttributeListener {

    // Public constructor is required by servlet spec
    public Listener() {
    }

    // -------------------------------------------------------
    // ServletContextListener implementation
    // -------------------------------------------------------
    public void contextInitialized(ServletContextEvent sce) {
      /* This method is called when the servlet context is
         initialized(when the Web application is deployed). 
         You can initialize servlet context related data here.
      */
    }

    public void contextDestroyed(ServletContextEvent sce) {
      /* This method is invoked when the Servlet Context 
         (the Web application) is undeployed or 
         Application Server shuts down.
      */
    }

    // -------------------------------------------------------
    // HttpSessionListener implementation
    // -------------------------------------------------------
    public void sessionCreated(HttpSessionEvent se) {
        /* Session is created. */
    }

    public void sessionDestroyed(HttpSessionEvent se) {
        /* Session is destroyed. */
    }

    // -------------------------------------------------------
    // HttpSessionAttributeListener implementation
    // -------------------------------------------------------

    public void attributeAdded(HttpSessionBindingEvent sbe) {
      /* This method is called when an attribute 
         is added to a session.
      */
    }

    public void attributeRemoved(HttpSessionBindingEvent sbe) {
      /* This method is called when an attribute
         is removed from a session.
      */
    }

    public void attributeReplaced(HttpSessionBindingEvent sbe) {
      /* This method is invoked when an attibute
         is replaced in a session.
      */
    }
}
​

javax.servlet.http包的監聽器接口：

1. HttpSessionActivationListener
2. HttpSessionAttributeListener
3. HttpSessionBindingListener
4. HttpSessionIdListener
5. HttpSessionListener
6. ServletContextListener
7. ServletRequestAttributeListener
8. ServletRequestListener
9. WriteListener