Servlet第五课：Cookie的使用

目标规划：

通过这一节课，我们可以懂得如何使用Cookie，以及如何获取Cookie中的内容。

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Cookie的详细概述。

1. Cookie 是保存在客户端的一个“键-值”对，用来标识用户的一些信息。

2. Cookie的应用
–在电子商务会话中标识用户
–对站点进行定制
–定向广告
3. 调用Cookie的构造函数，给出cookie的名称和cookie的值，二者都是字符串
Cookie c = new Cookie("userID", "a1234");
4. 如果要告诉浏览器将cookie存储到磁盘上，而非仅仅保存在内存中，使用setMaxAge (参数为秒数)
c.setMaxAge(60*60*24*7); // One week
5. 将Cookie放入到HTTP响应
response.addCookie(c);

6. 调用request.getCookies 获得这会得到Cookie对象组成的数组，在这个数组中循环，调用每个对象的getName，直到找到想要的cookie为止。

7.实例，创建cookie

我们首先创建一个Cookie信息：

核心代码：

Cookie c = new Cookie("goxuexi", "www.goxuexi.com");
c.setMaxAge(60*60*24*7);
response.addCookie(c);

全部代码：TestCookieServlet.java

package com.goxuexi.demo;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class TestCookieServlet
 */
@WebServlet("/TestCookieServlet")
public class TestCookieServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestCookieServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
Cookie c = new Cookie("goxuexi", "www.goxuexi.com");
c.setMaxAge(60*60*24*7);
response.addCookie(c);
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}

}

02.写一个获取Cookie的代码：

TestCookie.java

核心代码：

Cookie[] cs =  request.getCookies();
for (Cookie c : cs) {
System.out.println(c.getName()+":"+c.getValue());
}

全部代码：

package com.goxuexi.demo;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class TestCookie
 */
@WebServlet("/TestCookie")
public class TestCookie extends HttpServlet {
private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestCookie() {
        super();
        // TODO Auto-generated constructor stub
    }

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
Cookie[] cs =  request.getCookies();
               if(cs != null)
                for (Cookie c : cs) {
System.out.println(c.getName()+":"+c.getValue());
}
                 }
                   }

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}

}

8.实例-使用cookie检测初访者

//使用cookie检测初访者   
String result=null;    
        boolean newUser = true;    
        Cookie[] cookies = request.getCookies();    
        if(cookies!=null){    
                for(int i=0;i<cookies.length;i++){    
                        Cookie c = cookies[i];    
                        if((c.getName().equals("repeatVisitor"))&&(c.getValue().equals("yes"))){    
                        newUser = false;    
                            break;    
                        }    
                }    
        } 

if (newUser) {
Cookie returnVisitorCookie = new Cookie("repeatVisitor", "yes");
returnVisitorCookie.setMaxAge(60 * 60 * 24 * 365);
response.addCookie(returnVisitorCookie);
result = "Welcome Aboard";
} else {
result = "Welcome Back";
}
System.out.println(result);