求高手帮忙解决一下问题Java Web Cookie实例
package cn.com; import java.io.IOException;import java.io.PrintWriter;import java.util.LinkedHashMap;import java.util.Map; 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 CookieDemo3 extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //解决中文乱码问题 response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out=response.getWriter(); //输出所有的商品 out.write("本网站有如下商品：<br/>"); Map<String ,Book > map=Db.getAll(); for(Map.Entry<String, Book> entry:map.entrySet()) { Book book=entry.getValue(); out.print("<a href='/Cookie/CookieDemo4?id=' "+book.getId()+" target='_blank'>"+book.getName()+"</a><br/>"); } //显示用户曾经看过的商品 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("\\,"); for(String id:ids) { Book book=(Book)Db.getAll().get(id); out.print(book.getName()+"<br/>"); } } } } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }//Db作为数据库class Db{ private static Map<String ,Book> map=new LinkedHashMap(); static { map.put("1", new Book("1","Java WEB开发","WY","好书")); map.put("2", new Book("2","WEB开发","zt","一般")); map.put("3", new Book("3","程序设计","df","较好书")); map.put("4", new Book("4","计算机组成","as","一般好书")); map.put("5", new Book("5","编译原理","ty","很好书")); map.put("6", new Book("6","网络维护","hj","非常好书")); } public static Map getAll() { return map; }}//书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; } }package cn.com; import java.io.IOException;import java.io.PrintWriter;import java.util.Arrays;import java.util.Iterator;import java.util.LinkedList; import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class CookieDemo4 */public class CookieDemo4 extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=UTF-8"); PrintWriter out=response.getWriter(); //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.getDescription()+"<br/>"); out.write(book.getName()+"<br/>"); //构建Cookie ,回写给浏览器 String cookieValue=buildCookie(id,request); Cookie cookie=new Cookie("bookHistory",cookieValue); cookie.setMaxAge(30*24*3600); cookie.setPath("/Cookie"); response.addCookie(cookie); } private String buildCookie(String id, HttpServletRequest request) { // TODO Auto-generated method stub //如果用户没有带任何的Cookie过来 //如果用户带了Cookie来了包含在看过的id中，则要把id删掉 //带了Cookie过来了但是没有包含看过的id //带了Cookie过来但是没有包含 String 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) { return id; } @SuppressWarnings("rawtypes") LinkedList list=new LinkedList(Arrays.asList(bookHistory.split("\\,")));// if(list.contains(id))// {// list.remove(id);// list.addFirst(id);// }// else // {// if(list.size()>=3)// {// list.removeLast();// list.addFirst(id);// }// else// {// list.addFirst(id);// }// } if(list.contains(id)) { list.remove(id); } else if(list.size()>=3) { list.removeLast(); } list.addFirst(id); StringBuffer sb=new StringBuffer(); Iterator it=list.iterator(); while(it.hasNext()) { sb.append(id+","); } return sb.deleteCharAt(sb.length()-1).toString(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }