详细学习Java Cookie技术(用户登录、浏览、访问权限)

摘要：本章文章详细讲解：1、Cookie基本用法演示2、演示Cookie的访问权限3、演示Cookie的删除4、利用Cookie显示用户上次登录的...

本章文章详细讲解：

1、Cookie基本用法演示

2、演示Cookie的访问权限

3、演示Cookie的删除

4、利用Cookie显示用户上次登录的时间

5、利用Cookie技术显示用户最近浏览的若干个图片

6、测试火狐浏览器到底支持多少个Cookie和一个Cookie最大为多大

1、Cookie基本用法演示

index.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> </head> <body> <h1>演示Cookie技术</h1> <a href="CookieDemo">Cookie基本用法演示</a><br/> </body> </html>

web.xml:

<"1.0" encoding="UTF-8"?> <web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name> <servlet> <servlet-name>CookieDemo</servlet-name> <servlet-class>cn.hncu.servlets.CookieDemo</servlet-class> </servlet> <servlet-mapping> <servlet-name>CookieDemo</servlet-name> <url-pattern>/CookieDemo</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>

CookieDemo.java:

package cn.hncu.servlets; import java.io.IOException; import java.io.PrintWriter; import java.net.URLDecoder; import java.net.URLEncoder; import java.util.Random; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CookieDemo extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); //向客户端写cookie Random r = new Random(); int n =r.nextInt(100); String name = "jack";//cookie的格式：key=value Cookie c = new Cookie("name", name+n); c.setMaxAge(60*60);//设置过期时间，以秒为单位 c.setPath( request.getContextPath() );//该路径是: /项目名 //Cookie机制中，是通过path来控制权限的。只有<url-pattern>和该path相同或是它的子路径的servlet才能够访问该cookie //如果把一个cookie的path设为项目根目录，那么该项目下的所有servlet都能够访问它 response.addCookie(c); //这一段演示cookie带中文 String str = "我带中文"; str = URLEncoder.encode(str, "utf-8");//中文设置编码！！！urlencode编码 Cookie cStr = new Cookie("str", str); //如果不设置setMaxAge，则浏览器一关闭就过期 cStr.setPath("/"); response.addCookie(cStr); //读取客户端发过来的cookie Cookie cs[] = request.getCookies();//读取cookie if(cs!=null){//防范一下 for(Cookie cc:cs){ String name2 = cc.getName(); String val = cc.getValue(); val = URLDecoder.decode(val, "utf-8");//原来是怎么编码的，就怎么解码！中文解码，ascii是原样的！ out.print(name2+"="+val+"<br/>"); } } out.print("Cook保存成功！"); } }

演示结果：

第一次点击时！session下次讲！tomcat自动生成发给客户端的！

再次进入时！

name+n–因为后面的n一直在随机生成，这个点击总是显示的是前一个的信息！

2、演示Cookie的访问权限

index.jsp:

<a href="servlet/CookieDemo2">演示Cookie的访问权限</a><br/> web.xml: <servlet> <servlet-name>CookieDemo2</servlet-name> <servlet-class>cn.hncu.servlets.CookieDemo2</servlet-class> </servlet> <servlet-mapping> <servlet-name>CookieDemo2</servlet-name> <url-pattern>/servlet/CookieDemo2</url-pattern> </servlet-mapping>

CookieDemo2.java:

package cn.hncu.servlets; import java.io.IOException; import java.io.PrintWriter; import java.util.Random; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CookieDemo2 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); //向客户端写Cookie Random r = new Random(); int n =r.nextInt(100); Cookie c = new Cookie("age", ""+n); c.setMaxAge(60*60);//过期时间 c.setPath( request.getContextPath()+"/servlet/CookieDemo2" );//Cookie机制中,是通过path来控制权限的 //由于CookieDemo的url-pattern是项目根目录/CookieDemo，不是当前cookie所设路径的子目录，因此无法访问到该cookie //注意！！！path不一样，那么cookie是不同的对象，也就是不会覆那个名字相同的cookie！ response.addCookie(c); //读取从客户端发来的cookie Cookie cs[] = request.getCookies(); if(cs!=null){ for(Cookie cc:cs){ String name = cc.getName(); String val = cc.getValue(); out.print("22222--"+name+"="+val+"<br/>"); } } out.print("Cookie保存成功！"); } }

演示结果：

先进入CookieDemo2的页面，能访问到CookieDemo的name-cookie

再进入CookieDemo的页面，不能访问到CookieDemo2的age-cookie

3、演示Cookie的删除

index.jsp:

<a href="servlet/DelCookieDemo"> 演示Cookie的删除 </a><br/>

web.xml:

<servlet> <servlet-name>DelCookieDemo</servlet-name> <servlet-class>cn.hncu.servlets.DelCookieDemo</servlet-class> </servlet> <servlet-mapping> <servlet-name>DelCookieDemo</servlet-name> <url-pattern>/servlet/DelCookieDemo</url-pattern> </servlet-mapping>

DelCookieDemo.java:

演示结果：

这个时候，name还存在的。

我们访问DelCookieDemo.

再去第一个链接看：

name已经没有了！

火狐会自动删除过期的cookie：

4、利用Cookie显示用户上次登录的时间

index.jsp:

<a href="LoginServlet">利用Cookie显示用户上次登录的时间</a>

web.xml:

<servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>cn.hncu.servlets.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/LoginServlet</url-pattern> </servlet-mapping>

LoginServlet.java:

package cn.hncu.servlets; import java.io.IOException; import java.io.PrintWriter; import java.text.SimpleDateFormat; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>演示利用Cookie显示用户上次登录的时间</TITLE></HEAD>"); out.println(" <BODY>"); //读取客户端的cookie Cookie cs[] = request.getCookies(); boolean boo = false; if(cs!=null){ for(Cookie c:cs){ //遍历 if("loginTime".equals(c.getName())){ String val =c.getValue(); long dt = Long.parseLong(val); Date d = new Date(dt); SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss"); out.print("您上次登录时间是："+sdf.format(d)); boo=true; break; } } } if(boo==false){//表示之前1年没有访问记录！因为下面我们保存的过期时间是一年 out.print("您最近一年是第一次访问。。。"); } //无论是新旧用户，都会以最近的时间俩创建一个Cookie，写到客户端。原来有了的，就是更新时间 Date d = new Date(); Cookie c = new Cookie("loginTime", ""+d.getTime() ); c.setPath(request.getContextPath()); c.setMaxAge(60*60*24*30*12); response.addCookie(c); out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } }

演示结果：

第一次访问;

再次访问：

5、利用Cookie技术显示用户最近浏览的若干个图片

index.jsp:

<a href="jsps/show.jsp">看美女--利用Cookie技术显示用户最近浏览的若干个图片</a>

web.xml:

<servlet> <servlet-name>ShowServlet</servlet-name> <servlet-class>cn.hncu.servlets.ShowServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ShowServlet</servlet-name> <url-pattern>/showImg</url-pattern> </servlet-mapping>

show.jsp:

<%@page import="java.io.File"%> <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <style type="text/css"> .span{ border:0px solid #000; width:100px; height:100px; overflow:hidden; } .span img{ max-width:100px; _width:expression(this.width > 100 " : this.width); } .spans{ border:0px solid #000; width:50px; height:50px; overflow:hidden; } .spans img{ max-width:50px; _width:expression(this.width > 50 " : this.width); } </style> </head> <body> <h1>看美女--利用Cookie技术显示用户最近浏览的若干个图片</h1> <a href="/myCookieWeb/jsps/show.jsp">看美女--利用Cookie技术显示用户最近浏览的若干个图片</a> <h3>最近浏览的图片：</h3> <> <% String str =null; Cookie cs[] = request.getCookies(); if(cs!=null){ for(Cookie c:cs){ if("images".equals(c.getName())){ str=c.getValue();// ***.jpg break; } } } if(str!=null){ String strs[] = str.split(","); for(String s:strs){ %> <span> <img src="<%=request.getContextPath()%>/imgs/<%=s%>" /> </span> <% } } %> <br/><hr/><br/> <% //利用file遍历所有的图片，显示出来。 String path = getServletContext().getRealPath("/imgs"); //System.out.printf(path);//D:apache-tomcat-7.0.30webappsmyCookieWebjsps File file = new java.io.File(path); File[] files = file.listFiles(); if(files!=null){ %> <% for(File f:files){ String imgName = f.getName(); %> <span> <a href="<%=request.getContextPath() %>/showImg?img=<%=imgName %>"> <img src="<%=request.getContextPath()%>/imgs/<%=imgName%>" /> </a> </span> <% } %> <% } %> </body> </html>

ShowServlet.java:

package cn.hncu.servlets; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ShowServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">"); out.println("<HTML>"); out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>"); out.println(" <BODY>"); String img = request.getParameter("img"); String imgStr = "<img src='"+request.getContextPath()+"/imgs/"+img+"'/>"; out.print(imgStr); //用Cookie记录用户访问过的图片信息 Cookie cs[] = request.getCookies(); boolean boo = false; if(cs!=null){ for(Cookie c:cs){ if("images".equals(c.getName())){//已经有了images这个cookie String imgs = c.getValue(); String imgStrs[] = imgs.split(","); boolean booStr = false; //防范点击重复的图片 for(int i=0;i<imgStrs.length;i++){ if(imgStrs[i].equals(img)){ if(i==1&&imgStrs.length==2){ imgs=imgStrs[i]+","+imgStrs[0]; }else if(i==2&&imgStrs.length==3){ imgs=imgStrs[i]+","+imgStrs[0]+","+imgStrs[1]; }else if(i==2&&imgStrs.length==3){ imgs=imgStrs[i]+","+imgStrs[0]+","+imgStrs[1]; } booStr=true; break; } } if(!booStr){ imgs = img+","+imgs;//采用如下方式会麻烦一点：imgs+","+img if(imgs.split(",").length>3){//如果访问的图片超过3次了 imgs = imgs.substring(0, imgs.lastIndexOf(","));//左包含，右不包含 } /*//如果这样写了，最好把上面的防范重复的图片，那个添加顺序倒过来 //imgs+","+img 方式： imgs = imgs+","+img; if(imgs.split(",").length>3){//如果访问的图片超过3次了 imgs = imgs.substring(imgs.indexOf(",")+1, imgs.length()); } */ } c.setValue(imgs);//更新 c.setMaxAge(60*60*24*30); c.setPath("/");//相当于把访问权限完全放开，即所有的项目都能访问 response.addCookie(c); boo=true; break; } } } if(boo==false){//表示首次访问，即浏览器中没有图片浏览的cookie Cookie c = new Cookie("images", img); c.setMaxAge(60*60*24*30); c.setPath("/"); response.addCookie(c); } out.println(" </BODY>"); out.println("</HTML>"); out.flush(); out.close(); } }

演示结果：

6、测试火狐浏览器到底支持多少个Cookie和一个Cookie最大为多大

index.jsp:

<a href="servlet/HowManyCookieServlet">测试火狐浏览器到底支持多少个Cookie和一个Cookie最大为多大 </a><br/>

web.xml:

<servlet> <servlet-name>HowManyCookie</servlet-name> <servlet-class>cn.hncu.servlets.HowManyCookie</servlet-class> </servlet> <servlet-mapping> <servlet-name>HowManyCookie</servlet-name> <url-pattern>/servlet/HowManyCookieServlet</url-pattern> </servlet-mapping>

HowManyCookie.java:

package cn.hncu.servlets; import java.io.IOException; import java.io.PrintWriter; import java.net.URLDecoder; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class HowManyCookie extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); /* //测试个数--火狐47.0.1 最大支持110个 for(int i=1;i<=110;i++){ Cookie c = new Cookie("textNum"+i, ""+i); c.setMaxAge(60*15); c.setPath("/"); response.addCookie(c); } */ //测试大小 ---4092字节为最大支持的单个cookie存储 String s =""; for(int i=0;i<4092;i++){ s+="1"; } Cookie c = new Cookie("test", s); c.setMaxAge(60*15); c.setPath("/"); response.addCookie(c); Cookie cs[] = request.getCookies();//读取cookie if(cs!=null){//防范一下 for(Cookie cc:cs){ String key = cc.getName(); String val = cc.getValue(); out.print(key+"="+val+" "); } } } }

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