本章文章詳細講解：
1、Cookie基本用法演示
2、演示Cookie的訪問權限
3、演示Cookie的刪除
4、利用Cookie顯示用戶上次登錄的時間
5、利用Cookie技術顯示用戶最近瀏覽的若干個圖片
6、測試火狐瀏覽器到底支持多少個Cookie和一個Cookie最大為多大
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技術</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(); //向客戶端寫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);//設置過期時間，以秒為單位c.setPath( request.getContextPath() );//該路徑是: /項目名//Cookie機制中，是通過path來控制權限的。只有<url-pattern>和該path相同或是它的子路徑的servlet才能夠訪問該cookie //如果把一個cookie的path設為項目根目錄，那麼該項目下的所有servlet都能夠訪問它response.addCookie(c); //這一段演示cookie帶中文String str = "我帶中文"; str = URLEncoder.encode(str, "utf-8");//中文設置編碼！ ！ ！ urlencode編碼Cookie cStr = new Cookie("str", str); //如果不設置setMaxAge，則瀏覽器一關閉就過期cStr.setPath("/"); response.addCookie(cStr); //讀取客戶端發過來的cookie Cookie cs[] = request.getCookies();//讀取cookie if(cs!=null){//防範一下for(Cookie cc:cs){ String name2 = cc.getName(); String val = cc.getValue(); val = URLDecoder.decode(val, "utf-8");//原來是怎麼編碼的，就怎麼解碼！ 中文解碼，ascii是原樣的！ out.print(name2+"="+val+"<br/>"); } } out.print("Cook保存成功！"); }}演示結果：
第一次點擊時！ session下次講！ tomcat自動生成發給客戶端的！
再次進入時！
name+n因為後面的n一直在隨機生成，這個點擊總是顯示的是前一個的信息！
2、演示Cookie的訪問權限
index.jsp:
<a href="servlet/CookieDemo2">演示Cookie的訪問權限</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(); //向客戶端寫Cookie Random r = new Random(); int n =r.nextInt(100); Cookie c = new Cookie("age", ""+n); c.setMaxAge(60*60);//過期時間c.setPath( request.getContextPath()+"/servlet/CookieDemo2" );//Cookie機制中,是通過path來控制權限的//由於CookieDemo的url-pattern是項目根目錄/CookieDemo，不是當前cookie所設路徑的子目錄，因此無法訪問到該cookie //注意！ ！ ！ path不一樣，那麼cookie是不同的對象，也就是不會覆那個名字相同的cookie！ response.addCookie(c); //讀取從客戶端發來的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！"); }}演示結果：
先進入CookieDemo2的頁面，能訪問到CookieDemo的name-cookie
再進入CookieDemo的頁面，不能訪問到CookieDemo2的age-cookie
3、演示Cookie的刪除
index.jsp:
<a href="servlet/DelCookieDemo"> 演示Cookie的刪除</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){ //要想遍歷到"name"這個cookie，當前servlet必須要有讀的權限，即servlet的url-pattern必須是該cookie所設路徑或者是其所設路徑的子路徑//刪除name這個cookie if("name".equals(c.getName())){ c.setPath( request.getContextPath() );//刪除時是通過這一句來判斷權限的！這裡必須和原來所設的路徑完全一樣才能刪除，否則不能刪除！ //對於上句，我的個人理解是：因為如果你這個路徑設置不同了，其實只是相當與新開了一個cookie，這個新cookie的到期時間是0，name是"name" c.setMaxAge(0);//到期時見設為0，即是刪除---此處只是設置刪除標識response.addCookie(c); } } } }}演示結果：
這個時候，name還存在的。
我們訪問DelCookieDemo.
再去第一個鏈接看：
name已經沒有了！
火狐會自動刪除過期的cookie：
4、利用Cookie顯示用戶上次登錄的時間
index.jsp:
<a href="LoginServlet">利用Cookie顯示用戶上次登錄的時間</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顯示用戶上次登錄的時間</TITLE></HEAD>"); out.println(" <BODY>"); //讀取客戶端的cookie Cookie cs[] = request.getCookies(); boolean boo = false; if(cs!=null){ for(Cookie c:cs){ //遍歷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("您上次登錄時間是："+sdf.format(d)); boo=true; break; } } } if(boo==false){//表示之前1年沒有訪問記錄！因為下面我們保存的過期時間是一年out.print("您最近一年是第一次訪問。。。"); } //無論是新舊用戶，都會以最近的時間倆創建一個Cookie，寫到客戶端。原來有了的，就是更新時間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(); }}演示結果：
第一次訪問;
再次訪問：
5、利用Cookie技術顯示用戶最近瀏覽的若干個圖片
index.jsp:
<a href="jsps/show.jsp">看美女--利用Cookie技術顯示用戶最近瀏覽的若干個圖片</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技術顯示用戶最近瀏覽的若干個圖片</h1> <a href="/myCookieWeb/jsps/show.jsp">看美女--利用Cookie技術顯示用戶最近瀏覽的若干個圖片</a> <h3>最近瀏覽的圖片：</h3> <!-- 添加最近3次瀏覽的圖片--> <% 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> <img src="<%=request.getContextPath()%>/imgs/<%=s%>" /> </span> <% } } %> <br/><hr/><br/> <% //利用file遍歷所有的圖片，顯示出來。 String path = getServletContext().getRealPath("/imgs"); //System.out.printf(path);//D:/apache-tomcat-7.0.30/webapps/myCookieWeb/jsps 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記錄用戶訪問過的圖片信息Cookie cs[] = request.getCookies(); boolean boo = false; if(cs!=null){ for(Cookie c:cs){ if("images".equals(c.getName())){//已經有了images這個cookie String imgs = c.getValue(); String imgStrs[] = imgs.split(","); boolean booStr = false; //防範點擊重複的圖片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;//採用如下方式會麻煩一點：imgs+","+img if(imgs.split(",").length>3){//如果訪問的圖片超過3次了imgs = imgs.substring(0, imgs.lastIndexOf(","));//左包含，右不包含} /*//如果這樣寫了，最好把上面的防範重複的圖片，那個添加順序倒過來//imgs+","+img 方式： imgs = imgs+","+img; if(imgs.split(",").length>3){//如果訪問的圖片超過3次了imgs = imgs.substring(imgs.indexOf(",")+1, imgs.length()); } */ } c.setValue(imgs);//更新c.setMaxAge(60*60*24*30); c.setPath("/");//相當於把訪問權限完全放開，即所有的項目都能訪問response.addCookie(c); boo=true; break; } } } if(boo==false){//表示首次訪問，即瀏覽器中沒有圖片瀏覽的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(); }}演示結果：
6、測試火狐瀏覽器到底支持多少個Cookie和一個Cookie最大為多大
index.jsp:
<a href="servlet/HowManyCookieServlet">測試火狐瀏覽器到底支持多少個Cookie和一個Cookie最大為多大</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(); /* //測試個數--火狐47.0.1 最大支持110個for(int i=1;i<=110;i++){ Cookie c = new Cookie("textNum"+i, ""+i); c.setMaxAge(60*15); c.setPath("/"); response.addCookie(c); } */ //測試大小---4092字節為最大支持的單個cookie存儲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();//讀取cookie if(cs!=null){//防範一下for(Cookie cc:cs){ String key = cc.getName(); String val = cc.getValue(); out.print(key+"="+val+" "); } } }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。