监听器

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   在部署web应用是产生，即用户第一次访问之前已经产生，在重新部署web应用时，后销毁原监听器，再产生新的监听器

package cn.itcast.web.listener;

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

//事件监听器[用于监听ServletContext对象产生和销毁]
public class MyServletContextListener implements ServletContextListener{
	public MyServletContextListener(){
		System.out.println("空参构造");
		System.out.println(this.hashCode());
	}
	//产生
	public void contextInitialized(ServletContextEvent sce) {
		System.out.println("ServletContext产生");
		System.out.println(this.hashCode());
	}
	//销毁
	public void contextDestroyed(ServletContextEvent sce) {
		System.out.println("ServletContext销毁");
		System.out.println(this.hashCode());
	}
}

package cn.itcast.web.listener;

import java.util.Date;

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

//监听器[用于监听HttpSesison产生和销毁]
public class MyHttpSessionListener implements HttpSessionListener {
	//产生
	public void sessionCreated(HttpSessionEvent se) {
		HttpSession session = se.getSession();
		System.out.println(session.getId());
		System.out.println("sessionCreated()" + new Date().toLocaleString());
	}
	//销毁
	public void sessionDestroyed(HttpSessionEvent se) {
		HttpSession session = se.getSession();
		System.out.println(session.getId());
		System.out.println("sessionDestroyed()");
		System.out.println("sessionCreated()" + new Date().toLocaleString());
	}
}

package cn.itcast.web.listener;

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

//监听器[用于监听ServletRequest对象的产生和销毁]
public class MyServletRequestListener implements ServletRequestListener {
	//产生
	public void requestInitialized(ServletRequestEvent sre) {
		System.out.println("requestInitialized()");
	}
	//销毁
	public void requestDestroyed(ServletRequestEvent sre) {
		System.out.println("requestDestroyed()");
	}
}

监听器

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原文地址：http://my.oschina.net/u/2356176/blog/468108