【JSP开发】利用cookie实现商品浏览记录

在主页中显示商品，点击商品可以查看商品的具体信息，带用户浏览完之后，回到主页，就会看到自己曾经浏览过什么商品。


商品主页Servlet

CookieDemo3.java:package cn.edu.cookie;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;//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.setContentType("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();for(Map.Entry<String, Book> entry :map.entrySet()){Book book=entry.getValue();out.print("<a href='/day07/CookieDemo4?id="+book.getId()+"' terget='_blank'>"+book.getName()+"</a><br/>");}   //2.输出用户曾经看过的商品out.print("您曾经看过如下商品：<br/>");Cookie cookies[]= request.getCookies();for(int i=0;cookies!=null&&i<cookies.length;i++){//是不是要加if(cookies[i].getName().equals("BookHistory"))判断？    String ids[]=cookies[i].getValue().split("\\,");    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);}}//如果有检索数据的需求，用双列（Map）的容器，若没有用单列的（List）//模拟数据库class Db{private static Map<String,Book> map=new LinkedHashMap();//HashMap取出来和存进去的顺序不是一致的（自己测试）//类初始化代码（写在静态代码块里）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;}}class Book{private String id;private String name;private String author;private String description;public Book(){super();}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;}}

CookieDemo4.java是每件商品的详细信息Servlet，在这里，cookie中的"BookHistory"就是存储的浏览记录，记录的是
浏览每件商品的id记录顺序的字符串。组建该字符串的时候需要注意一下四种情况:
1.当一件商品都没有浏览过时，即BookHistory=null 
此时加入的商品直接组成字符串CookieValue即可，假设此时浏览过id=1的商品，
CookieValue="1";

2.当浏览的商品是以前浏览过的，即BookHistory="2,5,1"的时候此时又浏览了id=1的

商品，这个时候，就要找到原来的那个id，删除它，将此次浏览的记录加入到最前面。

即BookHistory="2,5,1"变成了BookHistory="1,2,5"

3.由于我们的商品浏览记录有限，只记录前三个，所以每当新的记录加入的时候，要判断
是否满三个，满了的话，删除最后一个，将最新的加入到最前面。
如BookHistory=2,5,4，当又浏览了1商品，要改成BookHistory=1,2,5

4.如果不满3个，又不和以前的重复，直接将记录加在最前面即可
如BookHistory=2,5的时候，又浏览了1商品，此时BookHistory=1,2,5

CookieDemo4.java

package cn.edu.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.Arrays;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;//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.setContentType("text/html;charset=UTF-8");PrintWriter out=response.getWriter();//根据用户带过来的id，显示相应商品的详细信息//getParameter是拿到客户机带过来的数据(通过表单和链接传递的参数使用getParameter)        String id =request.getParameter("id");//当两个Web组件之间为转发关系时采用getAttribute        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/>");        //构建cookie，回写给浏览器                /*一个web应用最多能被浏览器记录20个左右的cookie                           所以这里要把大量的cookie记录到一起，记录成一个cookie*/        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) {//四种cookie情况//BookHistory=null   1   1//BookHistory=2,5,1   1   1,2,5//BookHistory=2,5,4   1   1,2,5//BookHistory=2,5   1   1,2,5String 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){return id;}//分割成数组，之后将数组转成集合,集合转成链表LinkedList<String> list=new LinkedList(Arrays.asList(BookHistory.split("\\,")));//分情况分配新的cookie值if(list.contains(id)){//BookHistory=2,5,1   1   1,2,5list.remove(id);list.addFirst(id);}else{if(list.size()>=3){//BookHistory=2,5,4   1   1,2,5list.removeLast();list.addFirst(id);}else{//BookHistory=2,5   1   1,2,5//BookHistory=null   1   1list.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);}}

至此，介绍了使用cookie记录商品浏览记录的小例子。

转载请注明出处:http://blog.csdn.net/acmman