Cookie

会话：

保存会话数据的两种技术：

Cookie技术：

Session技术：

Cookie API：

Cookie应用：

Servlet代码：

//代表网站首页public class CookieDemo1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");response.setHeader("Content-Type","text/html;charset=UTF-8");PrintWriter out = response.getWriter();out.print("<a href='/day07/servlet/CookieDemo2'>清除上次访问时间</a></br>");out.print("您上次访问时间是：");//获得用户的时间cookieCookie cookies[] = request.getCookies();for(int i = 0 ; cookies!=null&&i<cookies.length;i++){if(cookies[i].getName().equals("lastAccessTime")){long cookieValue = Long.parseLong(cookies[i].getValue());//得到用户上次访问时间(转成long类型，即毫秒值)Date date = new Date(cookieValue);out.print(date.toLocaleString());}}//给用户回送最新的访问时间Cookie cookie = new Cookie("lastAccessTime",System.currentTimeMillis()+"");cookie.setMaxAge(1*30*24*3600);//设置cookie有效时间为1个月cookie.setPath("/day07");//设置cookie有效路径response.addCookie(cookie);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

public class CookieDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//要想清除cookie，则setMaxAge(0)，而且其他属性必须一致，比如pathCookie cookie = new Cookie("lastAccessTime",System.currentTimeMillis()+"");cookie.setMaxAge(0);cookie.setPath("/day07");response.addCookie(cookie);response.setStatus(302);response.setHeader("Location", "/day07/servlet/CookieDemo1");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

Cookie细节：

Cookie案例—显示商品浏览记录：

Servlet代码：

//商品类（书籍）class Book{private String id;private String name;private String author;private String description;public Book() {super();// TODO Auto-generated constructor stub}public Book(String id, String name, String author, String description) {super();this.id = id;this.name = name;this.author = author;this.description = description;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}}

//数据库(如果有检索数据需求，则用双列(Map)，如果不检索，则用单列(List))class Db{private static Map<String,Book> map = new LinkedHashMap();  //如果用HashMap，则获取商品顺序和存入顺序不一致，hashMap是根据hash值排列的//静态块，一使用Db类就自动执行static{map.put("1", new Book("1","javaweb开发","老张","一本好书"));map.put("2", new Book("2","jdbc开发","老张","一本好书"));map.put("3", new Book("3","spring开发","老黎","一本好书"));map.put("4", new Book("4","struts开发","老毕","一本好书"));map.put("5", new Book("5","android开发","老黎","一本好书"));}public static Map getAll(){return map;}}

//代表首页的servletpublic class CookieDemo3 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");response.setHeader("Content-Type", "text/html;charset=UTF-8");PrintWriter out = response.getWriter();//1.输出网站所有商品out.write("本网站有如下商品：<br/>");Map<String, Book> map = Db.getAll();//1.迭代map要把map先用entrySet方法转成Set//2.用增强for循环对map迭代，迭代出的每一个都是Map.Entryfor(Map.Entry<String, Book> entry : map.entrySet()){Book book = entry.getValue();out.print("<a href='/day07/servlet/CookieDemo4?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a><br/>");}//2.显示用户曾经看过的商品out.print("<br/>您曾经看过如下商品：<br/>");Cookie cookies[] = request.getCookies();for(int i = 0;cookies!=null&&i<cookies.length;i++){if(cookies[i].getName().equals("bookHistory")){String ids[] = cookies[i].getValue().split("\\,");//用逗号分割，用\\转义，确保不出问题for(String id : ids){Book book = (Book)Db.getAll().get(id);out.print(book.getName()+"<br/>");}}}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

//显示商品详细信息的servletpublic class CookieDemo4 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTF-8");response.setHeader("Content-Type", "text/html;charset=UTF-8");PrintWriter out = response.getWriter();//1.根据用户带过来的id,显示响应商品的详细信息String id = request.getParameter("id");Book book = (Book)Db.getAll().get(id);out.write(book.getId()+"<br/>");out.write(book.getAuthor()+"<br/>");out.write(book.getName()+"<br/>");out.write(book.getDescription()+"<br/>");//2.构建cookie，回写给浏览器String cookieValue = buildCookie(id,request);Cookie cookie = new Cookie("bookHistory",cookieValue);cookie.setMaxAge(1*30*24*3600);cookie.setPath("/day07");response.addCookie(cookie);}private String buildCookie(String id, HttpServletRequest request) {//当前cookiez值当前浏览id  回送cookie值//bookHistory=null11//bookHistory=2,5,111,2,5//bookHistory=2,5,411,2,5//bookHistory=2,511,2,5String bookHistory = null;Cookie cookies[] = request.getCookies();for(int i = 0;cookies!=null&&i<cookies.length;i++){if(cookies[i].getName().equals("bookHistory")){bookHistory=cookies[i].getValue();}}//if(bookHistory==null){////bookHistory=null11//return id;//}////LinkedList<String> list = new LinkedList(Arrays.asList(bookHistory.split("\\,")));//if(list.contains(id)){////bookHistory=2,5,111,2,5//list.remove(id);//list.addFirst(id);//}//else{////bookHistory=2,5,411,2,5//if(list.size()>=3){//list.removeLast();//list.addFirst(id);//}//else{////bookHistory=2,511,2,5//list.addFirst(id);//}//}if(bookHistory==null){return id;}//先把bookHistory字符串按","拆分为数组，再用Arrays.asList把数组转为List集合，再把List集合转为LinkedList，因为LinkedList对于节点的增删改查很方便LinkedList<String> list = new LinkedList(Arrays.asList(bookHistory.split("\\,")));if(list.contains(id)){list.remove(id);}else{if(list.size()>=3){list.removeLast();}}list.addFirst(id);StringBuffer sb = new StringBuffer();for(String bid : list){sb.append(bid+",");}return sb.deleteCharAt(sb.length()-1).toString();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}