最近好烦~ 不过没什么大不了的
一个商品的展示界面，可以看到你以前浏览过的的界面。利用cookie
/**
* 商品的列表界面
*/
public class Servlet_products extends HttpServlet {
public static final String bookHistory="bookHistory";
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1、展示商品的列表
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("商品的信息如下"+"<br/>");
HashMap<String, Book> map=(HashMap<String, Book>) DB.getAll();
Set<Entry<String, Book>> set = map.entrySet();
for (Entry<String, Book> entry : set) {
Book book=entry.getValue();
//展示商品的数据
out.write("<a href='/Demo2/Servlet_productInfo?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a>");
out.write("<br/>");
}
//2.展示以前浏览过的数据
out.write("<br/><br/>您曾经浏览过的商品:<br/>" );
Cookie[] cookies = request.getCookies();
for (int i = 0;cookies!=null&& i < cookies.length; i++) {
Cookie c=cookies[i];
if(c.getName().equals(bookHistory))
{
//是这个界面给浏览器的
String value=c.getValue();
//我们存入用户浏览过商品的id 是 1_2_3 这种格式进行存储的
String ids[] = value.split("\\_");
for(String id: ids){
Book book = (Book) DB.getAll().get(id);
out.write(book.getName() + "<br/>");
}
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
//模拟数据库
public static class DB {
//有序的 map
public static LinkedHashMap<String,Book> map=new LinkedHashMap<String,Book>();
static {
//静态代码块 用于初始化 map的信息
map.put("1", new Book("1","javaweb开发","老张","一本好书"));
map.put("2", new Book("2","spring开发","老黎","一本好书"));
map.put("3", new Book("3","hibernate开发","老佟","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","ajax开发","老张","一本好书"));
}
public static Map<String,Book> getAll(){
return map;
}
}
//商品的信息
public static class Book {
private String id;
private String name;
private String author;//作者
private String description; //描述
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;
}
}
}
商品的详情界面
package jemo.cookie.demo;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
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;
import jemo.cookie.demo.Servlet_products.Book;
import jemo.cookie.demo.Servlet_products.DB;
/**
* 点击具体的商品挑转到界面
*/
public class Servlet_productInfo extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//1.根据用户带过来的id号，显示商品的详细信息
String id = request.getParameter("id");
Book book = (Book) DB.getAll().get(id);
out.write("您要查看的书的详细信息如下：<br/><br/>");
out.write(book.getId() + "<br/>");
out.write(book.getName() + "<br/>");
out.write(book.getAuthor() + "<br/>");
out.write(book.getDescription() + "<br/>");
//2.给用户回送包含当前商品id的cookie
String bookHistory = makeHistory(request,id); // 3_2
Cookie cookie = new Cookie(Servlet_products.bookHistory,bookHistory);
cookie.setMaxAge(1*30*24*3600);
response.addCookie(cookie);
}
/**
* 得到要给浏览器cookie
* @param request
* @param id
* @return
*/
private String makeHistory(HttpServletRequest request, String id) {
String bookHistory = null;
Cookie cookies[] = request.getCookies();
for(int i=0;cookies!=null&&i<cookies.length;i++){
if(cookies[i].getName().equals(Servlet_products.bookHistory)){
bookHistory = cookies[i].getValue();
}
}
// bookHistory=null 1 bookHistory=1
// bookHistory=3_1_5 1 bookHistory=1_3_5
// bookHistory=3_2_5 1 bookHistory=1_3_2
// bookHistory=3_2 1 bookHistory=1_3_2
// bookHistory=null 1 bookHistory=1
if(bookHistory==null){
return id;
}
List l = Arrays.asList(bookHistory.split("\\_")); //[3,4] //数组 链接
LinkedList<String> list = new LinkedList();//对数据增删更有效
list.addAll(l);
if(list.contains(id)){
// bookHistory=3_1_5 1 bookHistory=1_3_5
list.remove(id);
list.addFirst(id);
}else{
if(list.size()>=3){
// bookHistory=3_2_5 1 bookHistory=1_3_2
list.removeLast();
list.addFirst(id);
}else{
// bookHistory=3_2 1 bookHistory=1_3_2
list.addFirst(id);
}
}
StringBuffer sb = new StringBuffer(); //2_3_4
for(String lid: list){
sb.append(lid + "_");
}
return sb.deleteCharAt(sb.length()-1).toString();//删除最后的_
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
