cookie小实例第二弹------浏览记录

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cookie小实例第二弹——浏览记录

这是一个简陋的小实例，用来记录浏览过的图书信息。主要三个类。

1. DBUtils           存储图书数据用的；2. ShowAllBooks      展示所有图书信息；3. ShowBookDetails   显示单本图书详细信息；

一切都在注释中

package com.samblack323.util;import java.util.HashMap;import java.util.Map;import com.samblack323.entity.Book;public class DBUtils {  private static Map<String,Book> books = new HashMap<String,Book>();  //直接搞四本书，简单粗暴  static {        books.put("1", new Book("1", "金瓶梅", 20, "王瑞鑫"));        books.put("2", new Book("2", "葵花宝典", 20, "杨成毅"));        books.put("3", new Book("3", "九阴真经", 30, "陈光"));        books.put("4", new Book("4", "玉女心经", 10, "陈志家"));  }  //得到所有书，便于展示所有商品  public static Map<String,Book> getAllBooks() {      return books;  }  //根据ID等到书，便于展示详细信息  public static Book getBookById(String id) {       return books.get(id);  }}

package com.samblack323.service;import java.io.IOException;import java.io.PrintWriter;import java.util.Map;import java.util.Map.Entry;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 com.samblack323.entity.Book;import com.samblack323.util.DBUtils;public class ShowAllBooks extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        //老样子，先把编码表弄好        req.setCharacterEncoding("UTF-8");          resp.setContentType("text/html;charset=UTF-8");        PrintWriter out = resp.getWriter();        //先拿到书再说        Map<String, Book> books = DBUtils.getAllBooks();        out.write("下面有四本好书，快来看看！" + "<br>");        //把书名都po出来，给上超链接，用get方式提交书的id到处理detail的servlet        for (Entry<String, Book> book : books.entrySet()) {            String id = book.getKey();            out.write("<a href='" + req.getContextPath() + "/cookie/showbookdetails?id=" + id + "' target='_blank'>" + book.getValue().getName()                    + "</a>" + "<br>");        }        out.write("-------------------------------" + "<br>");        out.write("最近浏览商品如下：" + "<br>");        //搞到所有cookie        Cookie[] cookies = req.getCookies();          Book book = null;        //别忘了判断cookie是否为空        for (int i = 0; cookies != null && i < cookies.length; i++) {               if ("BookId".equals(cookies[i].getName())) {                   //得到cookie中的value，即图书的id                String value = cookies[i].getValue();                         if (value != "") {                    //图书ID是用'-'拼接起来的字符串，咱们分割一下                    String[] booksId = value.split("-");                          //，总共四本书，倒着取值。j>1表示只浏览最近的3本(因为取不到缓存中下标为0的那本书)                    for (int j = booksId.length; j > 1; j--) {                        //注意角标不要越界                        book = DBUtils.getBookById(booksId[j-1]);                         //屏幕上走你                        out.write(book.getName() + "<br>");                          }                }            }        }    }}

package com.samblack323.service;import java.io.IOException;import java.io.PrintWriter;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 com.samblack323.entity.Book;import com.samblack323.util.DBUtils;public class ShowBookDetails extends HttpServlet{    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req,resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        //老样子，先把编码表弄好        req.setCharacterEncoding("UTF-8");        resp.setContentType("text/html;charset=UTF-8");        PrintWriter out = resp.getWriter();        //得到传来的id参数值        String id = req.getParameter("id");        //搞到这本书        Book book = DBUtils.getBookById(id);        //展示出来        out.write(book.toString());        //搞一个方法，拼接好图书id的值以便存储        String historyId = getId(id,req);        //搞一个cookie        Cookie cookie = new Cookie("BookId",historyId);        //设置路径        cookie.setPath("/");        //设置存货时长        cookie.setMaxAge(60*60);        //把cookie怼回客户端        resp.addCookie(cookie);    }    private String getId(String id, HttpServletRequest req) {        Cookie[] cookies = req.getCookies();        //如果还没有cookie就直接传当前图书id        if (cookies == null) {            return id;        }        String value = "";        StringBuffer sb = new StringBuffer();        for (int i = 0; i < cookies.length; i++) {            if ("BookId".equals(cookies[i].getName())) {    //找到这个cookie                value = cookies[i].getValue();                //搞到value，一个图书id与'-'拼接起来的字符串                if(value != "") {                    String[] booksId = value.split("-");        //value有值得话，切割成字符串数组                    for (int j = 0; j < booksId.length; j++) {                       //已经存在的记录中，不和当前图书id相同的，都给加到StringBuffer里面，并且后面跟一个'-'                        if(!id.equals(booksId[j])) {                                          sb.append(booksId[j]+"-");                                      }                    }                } else {    //如果有BookId的这个cookie，但是没值，一样返回当前id即可                    return id;                }            }        }        sb.append(id);   //循环结束，别忘了把最新的图书id加到Buffer里面        return sb.toString();    //怼回拼接完成的字符串    }}

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