大型网站一般都用cookie,因为session的会在客户端生成,是服务器压力增大,下面我来介绍一下,cookie的原理和使用
原理如图
使用方法:如如下代码demo1生成cookie,demo2获得cookie
demo1:
- import java.io.IOException;
- import java.util.Date;
-
- 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 CookieDemo1 extends HttpServlet {
-
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- Cookie cookie = new Cookie("lastTime", new Date().toLocaleString());
- cookie.setMaxAge(60 * 60);
- cookie.setValue(new Date().toLocaleString());
- cookie.setPath(request.getContextPath());// 设置的是有效路劲,如果没有设置,那就表示当前路径
- System.out.println(request.getContextPath());
- response.addCookie(cookie);
-
- }
-
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request, response);
- }
-
- }
demo2:
- package com.itcast.servlet;
-
- import java.io.IOException;
-
- 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 CookieDemo2 extends HttpServlet {
-
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- Cookie[] cookie = request.getCookies();
- for (int i = 0; cookie != null && i < cookie.length; i++) {
- if ("lastTime".equals(cookie[i].getName())) {
- response.getWriter().write(cookie[i].getValue());
- System.out.println(cookie[i].getValue());
- } else if (cookie == null) {
- response.getWriter().write("您是首次访问本站");
- Cookie[] cookies = request.getCookies();
- }
- }
-
- } %ity="high" allowscriptaccess="always" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" style="z-index: 0;">
- import java.util.Collection;
- import java.util.LinkedHashMap;
- import java.util.Map;
-
- public class DB {
- private static Map<String, Book> books = new LinkedHashMap<String, Book>();
-
- public static Collection<Book> getAll() {
- return books.values();
- }
-
- static {
- books.put("1", new Book("1", "php实战", "老路", "hello"));
- books.put("2", new Book("2", "android开发", "老徐", "110"));
- books.put("3", new Book("3", "jdbc开发", "老黎", "106"));
- books.put("4", new Book("4", "c++算法", "老方", "107"));
- }
-
- public static Book Findbook(String bookid) {
- return books.get(bookid);
- }
- }
3.这个类,有两个功能,第一个,显示全部的书,第二个,在你买书后,刷新能显示你曾经浏览过的书
- package com.itcast.servlet;
-
- import java.io.IOException;
- import java.io.PrintWriter;
- import java.util.Collection;
-
- 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 cn.itcast.cookie.javabean.Book;
- import cn.itcast.cookie.javabean.DB;
-
- public class ListBookServlet extends HttpServlet {
-
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- response.setContentType("text/html;charset=utf-8");
- PrintWriter out = response.getWriter();
- request.getParameter("id");
- // 获得商品
- Collection<Book> books = DB.getAll();
- // 显示商品
- for (Book book : books) {
- out.write("<a href='/day07_cookie/servlet/ShowBookInfo?id="
- + book.getId() + "'>" + book.getName() + "</a><br>");
-
- }
- String bookHistory = null;
- Cookie[] cookies = request.getCookies();
- for (int i = 0; cookies != null && i < cookies.length; i++) {
- if ("BookHistory".equals(cookies[i].getName())) {
- bookHistory = cookies[i].getValue();
- break;
- }
- }
-
- out.write("您浏览过的商品:</br>");
-
- String[] strs = bookHistory.split("\\-");// 将获得的字符串拆分,获取里面的id,用来找到每一本书
- for (int j = 0; j < strs.length; j++) {
- System.out.println("strs[i]=" + strs[j]);
- Book book = DB.Findbook(strs[j]);
- out.write(book.getName() + "</br>");
- }
-
- }
-
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request, response);
- }
-
- }
4.显示你购买商品的详细信息,并将你所有的购买的商品的id,拼接成一个1-2-3格式的字符串
- package com.itcast.servlet;
-
- import java.io.IOException;
- 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 cn.itcast.cookie.javabean.Book;
- import cn.itcast.cookie.javabean.DB;
-
- public class ShowBookInfo extends HttpServlet {
-
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- response.setContentType("text/html;charset=utf-8");
- String id = request.getParameter("id");
- Book book = DB.Findbook(id);
- String BookHistory = makeBookHistory(request, book.getId());
- response.getWriter().write(
- "" + book.getName() + "</br>" + book.getAuthor() + "</br>"
- + book.getPrice() + "</br>");
- Cookie cookie = new Cookie("BookHistory", BookHistory);
- response.addCookie(cookie);
-
- }
-
- private String makeBookHistory(HttpServletRequest request, String id) {
- Cookie[] cookies = request.getCookies();
- String BookHistory = null;
- for (int i = 0; cookies != null && i < cookies.length; i++) {
- if ("BookHistory".equals(cookies[i].getName())) {
-
- BookHistory = cookies[i].getValue();
- break;
- }
- }
- if (BookHistory == null) {
- return id;
- }
- String[] strs = BookHistory.split("-");//如果前面获得的id不是null,将返回来的字符串拆分,获得所有的id,存到String[]中
- List<String> list = Arrays.asList(strs);
- LinkedList<String> ids = new LinkedList<String>();//添加到LinkedList,是为了能按照先后顺序显示
- ids.addAll(list);
-
- if (ids.contains(id)) {// 如果有,移除,并加到第一个
- ids.remove(id);//
- ids.addFirst(id);
-
- }
- if (ids.size() == 3) {//最多显示3个浏览过的商品,如果超过,就删除最后一个
- ids.remove(ids.size() - 1);
-
- } else {
- ids.addFirst(id);
- }
- StringBuffer sb = new StringBuffer();
- for (String str : ids) {//将所有的id,合并成一个1-2-3的字符串,因为一次只能储存一个数据,在cookie中,所以用这个来储存多个id
- sb.append(str + "-");
-
- }
- sb.deleteCharAt(sb.length() - 1);
- return sb.toString();
- }
-
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request, response);
- }
-
- }
本站仅提供存储服务,所有内容均由用户发布,如发现有害或侵权内容,请
点击举报。