Cookie案例-显示商品流量历史记录

package 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 test1 extends HttpServlet {
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='test2?id=" + book.getId() + "' target='_blank' >" + book.getName()
+ "</a><br/>");
}

//显示用户曾经看过的商品
out.print("<br/>您曾经看过的商品：<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("\\,");
for (String id : ids) {
Book book = (Book) Db.getAll().get(id);
out.print(book.getName() + "<br/>");
}
}
}

}
}

//Db作为数据库
class Db {
private static Map<String, Book> map = new LinkedHashMap<String, Book>();
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<String, Book> getAll() {
return map;
}
}

//书
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;
}
}

package com;

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;

public class test2 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) {
//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;
}
LinkedList<String> list = new LinkedList<String>(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).append(",");
}
return sb.deleteCharAt(sb.length() - 1).toString();
}
}