cookie02--回显浏览过的商品-白红宇

cookie02--回显浏览过的商品

阅读量：5083 次

发布时间：2019-06-13

本文共 5157 字，大约阅读时间需要 17 分钟。

package cn.itcast.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 {		@Override	protected void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		//1. 输出网站所有的商品		request.setCharacterEncoding("utf-8");		response.setContentType("text/html;charset=utf-8");		PrintWriter writer = response.getWriter();		writer.write("本网站有如下商品:
"); // 浏览器换行用br,java用/r/n				//1.2 从DB中获取所有的商品信息		Map
     
       map = DB.getAll();		for(Map.Entry
      
        entry : map.entrySet()){			Book book = entry.getValue();			writer.print("
       "+  book.getName() +"
       
");		}				//2.显示用户曾经看过的商品		writer.print("
       
您曾经浏览过的商品: 
       
");		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("\\,"); //推荐转意				for( String id : ids) { // 通过id去db中查找对应的书					Book book = DB.getAll().get(id);					writer.print(book.getName() + "
       
");				}			}		}	}		protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException ,IOException {				this.doGet(request, response);	}}class DB{	//想存的数据的顺序与显示的顺序一致,用LinkedHashMap	private static Map
       
         map = new LinkedHashMap
        
         (); 		static{ //静态代码块确保只加载一次		map.put("1", new Book("1", "javaweb开发", "老张", "高薪书"));		map.put("2", new Book("2", "andorid开发", "老张", "高薪书"));		map.put("3", new Book("3", "ios开发", "老张", "高薪书"));		map.put("4", new Book("4", "javaEE开发", "老张", "高薪书"));		map.put("5", new Book("5", "疯狂的java开发", "老张", "高薪书"));	}		public static Map
         
           getAll(){		return map;	}}class Book{		private String id;	private String name;	private String author;	private String description;		public Book(){}	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.itcast.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;public class CookieDemo4 extends HttpServlet {		@Override	protected void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		request.setCharacterEncoding("utf-8");		response.setContentType("text/html;charset=utf-8");		PrintWriter out = response.getWriter();				//根据用户传过来的id,显示相应商品的详细信息		String id = request.getParameter("id");		Book book = DB.getAll().get(id);		out.write(book.getId() + "
");		out.write(book.getName() + "
");		out.write(book.getAuthor() + "
");		out.write(book.getDescription() + "
");				//构建cookie, 回写给浏览器		String cookieValue = buildCookie(id, request);		Cookie cookie = new Cookie("bookHistory", cookieValue);		cookie.setMaxAge(3600*24*30);		cookie.setPath(request.getContextPath());		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		//bookHistory = 2,5     1    1,2,5				Cookie[] cookies = request.getCookies();		String bookHistory = null;		for(int i = 0; cookies != null && i < cookies.length; i++) {			if(cookies[i].getName().equals("bookHistory")){				bookHistory = cookies[i].getValue();			}		}		if(bookHistory == null){ //第一次			return id;		}				LinkedList
     
       list = new LinkedList
      
       (Arrays.asList(bookHistory.split("\\,")));		/*if(list.contains(id)){ //当前浏览的商品在cookie中存在			list.remove(id); //把存在的删除			list.addFirst(id);//把当前的放在第一个		} else{ //不存在; 			if(list.size() >= 3){// 如何list满了把当前的放在第一个并删除最后一个				list.removeLast();				list.addFirst(id);			} else{ //直接添加到list头部				list.addFirst(id);			}		}*/				if(list.contains(id)){ 			list.remove(id);		} else{ 			if(list.size() >= 3){				list.removeLast();			} 		}		list.addFirst(id);				StringBuilder sb = new StringBuilder();		for(String bookId : list) {			sb.append(bookId).append(",");		}		sb.deleteCharAt(sb.length() - 1);		bookHistory = sb.toString();		return bookHistory;	}}