本章博客讲解：
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:
<?xml version="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:
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 DelCookieDemo extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
Cookie cs[] = request.getCookies();
if(cs!=null){
for(Cookie c:cs){
//要想遍历到"name"这个cookie，当前servlet必须要有读的权限，即servlet的url-pattern必须是该cookie所设路径或者是其所设路径的子路径
//删除name这个cookie
if("name".equals(c.getName())){
c.setPath( request.getContextPath() );//删除时是通过这一句来判断权限的！这里必须和原来所设的路径完全一样才能删除，否则不能删除！
//对于上句，我的个人理解是：因为如果你这个路径设置不同了，其实只是相当与新开了一个cookie，这个新cookie的到期时间是0，name是"name"
c.setMaxAge(0);//到期时见设为0，即是删除---此处只是设置删除标识
response.addCookie(c);
}
}
}
}
}
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 ? "100px" : this.width);
}
.spans{
border:0px solid #000;
width:50px;
height:50px;
overflow:hidden;
}
.spans img{
max-width:50px;
_width:expression(this.width > 50 ? "50px" : 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>
<!-- 添加最近3次浏览的图片 -->
<%
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 class="spans">
<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 class="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+" ");
}
}
}
}