显示商品历史浏览记录
废话不多说，直接上代码
package cn.itcast.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.Arrays;import java.util.Date;import java.util.LinkedList;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;//显示详细信息的servletpublic class CookieDemo4 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //根据用户带过来的id，显示相应的详细信息 response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String id=request.getParameter("id"); Book book=(Book)Db.getAll().get(id); out.write(book.getId()+"<br/>"); out.write(book.getName()+"<br/>"); out.write(book.getAuthor()+"<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);//1 个月 cookie.setPath("/day07"); response.addCookie(cookie); } private String buildCookie(String id, HttpServletRequest request) { //bookHistory =null 1 1 //bookHistory=2,5,1 1 1,2,5 //bookHistory=2,5,4 1 1,2,5 //bookHistroy=2,5 1 1,2,5 // 假如列表最多3个 String bookHistroy=null; Cookie cookies[]=request.getCookies(); for(int i=0;cookies!=null && i<cookies.length;i++){ if(cookies[i].getName().equals("bookHistory")){ bookHistroy=cookies[i].getValue(); } } if(bookHistroy==null) return id; //if(bookHistroy.contains(id))不能这样 21,23 也包括1 List<String> list=Arrays.asList(bookHistroy.split("\\,")); LinkedList <String>linkedlist=new LinkedList<String>(list); if(list.contains(id)){ linkedlist.remove(id); linkedlist.addFirst(id); }else{ if(list.size()>=3){ linkedlist.removeLast(); linkedlist.addFirst(id); }else linkedlist.addFirst(id); } StringBuffer sb=new StringBuffer(); for(String bid : linkedlist){ sb.append(bid+","); } return sb.deleteCharAt(sb.length()-1).toString(); }}