Cookie应用

1.添加cookie属性,显示输出cookie相关内容并设置存在时间

package com.tsinghua;

import javax.servlet.http.*;
import java.io.*;

public class CookieTest1 extends HttpServlet {
	public void doGet(HttpServletRequest req,HttpServletResponse res) {
		try {
			PrintWriter pw = res.getWriter();
			res.setContentType("text/html;charset=utf8");
			Cookie myCookie = new Cookie("pass","ok");
			//设置cookie存在时间
			myCookie.setMaxAge(30);
			//将cookie添加到客户端
			res.addCookie(myCookie);
			pw.println("Hello,current cookie's name is "+myCookie.getName()+",value is "+myCookie.getValue());
		}catch(Exception ex) {
			ex.printStackTrace();	
		}
	}
	public void doPost(HttpServletRequest req,HttpServletResponse res) {
		this.doGet(req,res);	
	}	
}

关键代码:

(1)新建Cookie   

　Cookie myCookie = new Cookie("String name","String value");        

(2)设置Cookie存在时间(单位:s)     

 myCookie.setMaxAge(int time);

(3)获取Cookie的名称       

 myCookie.getName();

(4)获取Cookie的值           

 myCookie.getValue();

(5)将Cookie添加到客户端         

 res.addCookie(myCookie);

(6)获取所有Cookie信息    

 Cookie []allCookies = req.getCookies();

开启tomcat,访问浏览器效果如下:

2.检验cookie某属性是否存在,根据cookie是否存在输出相应的信息

package com.tsinghua;

import javax.servlet.http.*;
import java.io.*;

public class CookieTest2 extends HttpServlet {
	public void doGet(HttpServletRequest req,HttpServletResponse res) {
		try {
			PrintWriter pw = res.getWriter();
			res.setContentType("text/html;charset=utf8");
			//获得所有cookie信息
			Cookie []allCookies = req.getCookies();
			if(allCookies!=null) {
				for(int i=0; i<allCookies.length; i++) {
					Cookie temp = allCookies[i];
					if(temp.getName().equals("pass")) {
						pw.println("pass="+temp.getValue());
						break;	
					} 
				}
			}else {
				pw.println("Cookie is not exisits or out-of-date");	
			}
		}catch(Exception ex) {
			ex.printStackTrace();	
		}	
	}
	public void doPost(HttpServletRequest req,HttpServletResponse res) {
		this.doGet(req,res);
	}	
}

Reload后,访问浏览器,若Cookie仍然存在,显示的效果图如下:

若Cookie不存在(在设置cookie存在的时间30s后访问),显示的效果如图如下: