13.JavaWeb基础监听器

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最新推荐文章于 2024-04-21 22:10:05 发布

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分类专栏： JavaWeb基础

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本文详细介绍了在Web开发中使用监听器进行监听application、session、request等操作的方法及其实现过程，包括如何实现监听事件、配置监听器以及通过测试代码验证监听效果。

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监听器俗称监听Servlet。主要的功能是负责监听Web的各种操作，当相关的事件触发

之后将产生事件，并对此事件进行处理。在Web中可以对request、session、application

属性进行监听操作。

一.对application监听

ApplicationListener：

package com.zyy.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class ApplicationListener implements ServletContextListener {

	public void contextDestroyed(ServletContextEvent event) {

		System.out.println("*************************Application销毁："
				+ event.getServletContext().getContextPath());

	}

	public void contextInitialized(ServletContextEvent event) {

		System.out.println("***************************Application初始化："
				+ event.getServletContext().getContextPath());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.ApplicationListener</listener-class>
  
  </listener>

ApplicationAttributeListener：

package com.zyy.listener;

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

public class ApplicationAttributeListener implements
		ServletContextAttributeListener {

	public void attributeAdded(ServletContextAttributeEvent event) {

		System.out.println("Application增加属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeRemoved(ServletContextAttributeEvent event) {

		System.out.println("Application删除属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeReplaced(ServletContextAttributeEvent event) {

		System.out.println("Application更新属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.ApplicationAttributeListener</listener-class>
  
  </listener>

测试代码：

<%

	this.getServletContext().setAttribute("CaMnter", "Save you from anything 07") ;
        this.getServletContext().setAttribute("CaMnter", "Save you from anything 07 forever") ;
	this.getServletContext().removeAttribute("CaMnter") ;

%>

刷新好多次页面得到如下：

二.对session监听

SessionListener：

package com.zyy.listener;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class SessionListener implements HttpSessionListener {

	public void sessionCreated(HttpSessionEvent event) {

		System.out.println("***** Session创建  id：" + event.getSession().getId());

	}

	public void sessionDestroyed(HttpSessionEvent event) {

		System.out.println("***** Session摧毁  id：" + event.getSession().getId());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.SessionListener</listener-class>
  
  </listener>

测试代码：

<%

	session.invalidate();

%>

刷新好多次页面得到如下：

SessionAttributeListener：

package com.zyy.listener;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class SessionAttributeListener implements HttpSessionAttributeListener {

	public void attributeAdded(HttpSessionBindingEvent event) {

		System.out.println("Session增加属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeRemoved(HttpSessionBindingEvent event) {

		System.out.println("Session删除属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeReplaced(HttpSessionBindingEvent event) {

		System.out.println("Session更新属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.SessionAttributeListener</listener-class>
  
  </listener>

测试代码：

<%

	session.setAttribute("CaMnter", "Save you from anything 07") ;
	session.removeAttribute("CaMnter");

%>

刷新好多次页面得到如下：

三.对request监听

RequestListener：

package com.zyy.listener;

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;

public class RequestListener implements ServletRequestListener {

	public void requestDestroyed(ServletRequestEvent event) {

		System.out.println("Request 销毁："
				+ event.getServletRequest().getRemoteAddr()
				+ event.getServletContext().getContextPath());

	}

	public void requestInitialized(ServletRequestEvent event) {

		System.out.println("Request 初始化："
				+ event.getServletRequest().getRemoteAddr()
				+ event.getServletContext().getContextPath());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.RequestListener</listener-class>
  
  </listener>

这个不需要测试代码，发布项目后，连接到即可。比如（http://127.0.0.1:8080/Listener）。

然后多次刷新后得到：

RequestAttributeListener：

package com.zyy.listener;

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

public class RequestAttributeListener implements
		ServletRequestAttributeListener {

	public void attributeAdded(ServletRequestAttributeEvent event) {

		System.out.println("Request增加属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeRemoved(ServletRequestAttributeEvent event) {

		System.out.println("Request删除属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

	public void attributeReplaced(ServletRequestAttributeEvent event) {

		System.out.println("Request更新属性：" + " name = " + event.getName()
				+ " ,value = " + event.getValue());

	}

}

web.xml：

  <listener>
  
  	<listener-class>com.zyy.listener.RequestAttributeListener</listener-class>
  
  </listener>

测试代码：

<%

	request.setAttribute("CaMnter", "Save you from anything 07") ;
	request.setAttribute("CaMnter", "Save you from anything 07 forever") ;
	request.removeAttribute("CaMnter") ;

%>