1. 会话管理概述
1.1 什么是会话
好比一次通话。打开浏览器，点击多次链接（发出多次请求和收到多次的响应），关闭浏览器，这个过程就是一次会话。
有功能 可以 文件 新建会话
1.2 解决的问题是什么
共享多次请求中产生的数据。比如购物车。
1.3 Application Session Cookie 生命周期 简要区别
|
方法 |
信息量大小 |
保存时间 |
应用范围 |
保存位置 |
|
Application |
任意大小 |
整个应用程序的生命期 |
所有用户 |
服务器端 |
|
Session |
小量,简单的数据 |
用户活动时间+一段延迟时间(一般为20分钟) |
单个用户 |
服务器端 |
|
Cookie |
小量,简单的数据 |
可以根据需要设定 |
单个用户 |
客户端 |
2. 客户端技术：Cookie
2.1 HTTP协议的消息头
请求消息头：Cookie 客户端向服务器端传递信息
响应消息头：Set-Cookie 服务器端向客户端传递信息
2.2 Cookie详解
l 属性：
name：Cookie的名称，必要的属性
value：Cookie的取值（不能为中文），必要的属性
-------------------以下为可选属性
path：Cookie的路径
默认值就是写cookie的那个资源的访问路径
比如：http://localhost:8080/day09_00_cookie/servlet/CookieDemo1 path就是/day09_00_cookie/servlet/
注意：
如果一个存在浏览器缓存中的cookie的路径是/day09/servlet/
当访问http://localhost:8080/day09/CookiePathDemo1时，
浏览器根本不带Cookie给服务器。浏览器比对的是cookie的路径和当前访问的资源的路径。
浏览器满足一下条件就会带cookie给服务器：
当前访问的地址的路径.startWith(已存cookie的路径)。
即：如果一个Cookie的路径设置为了当前应用，说明访问该网站的任何资源时浏览器都带该cookie给服务器。（开发中经常做的）
maxAge：Cookie的最大生存时间。默认是在浏览器的内存中。
domain：Cookie的域名（网站）。默认就是写cookie的那个资源所属的网站。
http://localhost:8080/day09_00_cookie/servlet/CookieDemo1域名就是localhost
version：版本号
comment:注释
u 把Cookie写给客户端：
HttpServletResponse.addCookie(Cookie c):实际上就是向客户端发送了一个响应消息头。
注意：客户端只能保存一个网站最多20个Cookie数据，总共最多300个。每个Cookie的大小不能超过4kb。
l 服务器端获取客户端带来的Cookie：
Cookie [] HttpServletRequest.getCookies();
注意：domain+path+name唯一确定一个Cookie。
2.3 3个案例
2.3.1 显示用户最近的访问时间
public class CookieDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("您上次访问的时间是：<a href='"+request.getContextPath()+"/servlet/ClearTimeServlet'>清除时间</a>");
//获取指定名称的cookie：lastAccessTime=毫秒值
Cookie cs[] = request.getCookies();
for(int i=0;cs!=null&&i<cs.length;i++){
if("lastAccessTime".equals(cs[i].getName())){
//找到了
long time = Long.parseLong(cs[i].getValue());
out.write(new Date(time).toLocaleString());
}
}
//把当前的时间写回去
Cookie c = new Cookie("lastAccessTime", System.currentTimeMillis()+"");
c.setMaxAge(Integer.MAX_VALUE);//单位是秒
response.addCookie(c);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//清除指定的cookie
public class ClearTimeServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//如何唯一定位要删除的cookie：domain+path+name
Cookie c = new Cookie("lastAccessTime", "");
c.setMaxAge(0);
response.addCookie(c);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
演示Cookie的path
public class CookiePathDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//path：/day09/servlet/
Cookie c = new Cookie("demoCookie", "aaa");
c.setPath(request.getContextPath());// 把路径改为 /day09
c.setMaxAge(Integer.MAX_VALUE);
// c.setDomain("itheima.com");//写了白写
response.addCookie(c);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
public class CookiePathDemo2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie cs[] = request.getCookies();
for(int i=0;cs!=null&&i<cs.length;i++){
if("demoCookie".equals(cs[i].getName())){
//找到了
response.getWriter().write(cs[i].getValue());
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
2.3.2 记住登录的用户名
public class LoginUIServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String username = "";
String checked = "";
//得到指定的cookie
Cookie cs[] = request.getCookies();
for(int i=0;cs!=null&&i<cs.length;i++){
if("loginInfo".equals(cs[i].getName())){
username = cs[i].getValue();
checked="checked='checked'";
break;
}
}
out.write("<form action='"+request.getContextPath()+"/servlet/LoginServlet' method='post'>");
out.write("用户名：<input type='text' name='username' value='"+username+"'/><br/>");
out.write("密码：<input type='password' name='password' value=''/><br/>");
out.write("记住用户名：<input type='checkbox' name='remember' "+checked+"/><br/>");
out.write("<input type='submit' value='登录'/>");
out.write("</form>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//验证用户名和密码是否正确：此处输什么都正确
String username = request.getParameter("username");
String password = request.getParameter("password");
String remember = request.getParameter("remember");//没有选中就是null
Cookie c = new Cookie("loginInfo", username);
c.setPath(request.getContextPath());
if(remember==null){
//没有选中：删cookie
c.setMaxAge(0);
}else{
//用户记住用户名：存cookie
c.setMaxAge(Integer.MAX_VALUE);
}
response.addCookie(c);
out.write("登录成功");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
2.3.3 显示 最近浏览的产品 （图书）
//book类
public class Book { private String id; private String name; private String price; private String author; private String 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 getPrice() { return price; } public void setPrice(String price) { this.price = price; } 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; } @Override public String toString() { return "Book [id=" + id + ", name=" + name + ", price=" + price + ", author=" + author + ", description=" + description + "]"; } public Book(String id, String name, String price, String author, String description) { super(); this.id = id; this.name = name; this.price = price; this.author = author; this.description = description; } public Book(){} }
//模拟数据
public class BookDB {
//key:书的id value：id对应的书
private static Map<String,Book> books = new HashMap<String,Book>();
static{
books.put("1", new Book("1", "葵花宝典", "10", "nius", "欲练此功，必须很牛"));
books.put("2", new Book("2", "欲女心经", "2", "xuez", "欲练此功，必须清纯"));
books.put("3", new Book("3", "倾城之恋", "20", "liuc", "爱情经典"));
books.put("4", new Book("4", "辟邪剑法", "10", "wangl", "欲练此功，必须很牛"));
books.put("5", new Book("5", "JavaWeb开发", "100", "yif", "经典著作"));
}
public static Map<String,Book> findAllBooks(){
return books;
}
public static Book findById(String bookId){
return books.get(bookId);
}
}
public class ShowAllBooksServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//显示所有的商品，提供查看详细内容的链接
out.write("<h1>本站有以下好书：</h1>");
Map<String, Book> books = BookDB.findAllBooks();
for(Map.Entry<String, Book> me:books.entrySet()){
out.write(me.getValue().getName()+" <a href='"+request.getContextPath()+"/servlet/ShowDetailsServlet?id="+me.getKey()+"' target='_blank'>查看详细</a><br/>");
}
//显示最近的浏览记录：3条 bookHistory=2-1-3
out.write("<hr/>您最近的浏览记录如下：<br/>");
Cookie cs[] = request.getCookies();
for(int i=0;cs!=null&&i<cs.length;i++){
if("bookHistory".equals(cs[i].getName())){
String value = cs[i].getValue();// 2-1-3
String ids[] = value.split("\-");
for(String id:ids){
out.write(BookDB.findById(id).getName()+"<br/>");
}
break;
}
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//显示商品的详细内容
//组织数据，向客户端写cookie
public class ShowDetailsServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//显示商品的详细内容
String id = request.getParameter("id");
Book book = BookDB.findById(id);
out.write(book.toString());
//组织数据，向客户端写cookie 3条 bookHistory=2-1-3
String bookId = makeId(id,request);
Cookie c = new Cookie("bookHistory", bookId);
c.setPath(request.getContextPath());
response.addCookie(c);
}
//组织数据
/*
客户端带来的cookie 当前访问的书的id 应该写回去的新id
cookie为null 1 bookHistory=1
cookie不为null，但没有bookHistory 1 bookHistory=1
bookHistory=1 2 bookHistory=2-1
bookHistory=1-2 3 bookHistory=3-1-2
bookHistory=1-2 2 bookHistory=2-1
bookHistory=1-2-3 4 bookHistory=4-1-2
bookHistory=1-2-3 2 bookHistory=2-1-3
*/
private String makeId(String id, HttpServletRequest request) {
// cookie为null 1 bookHistory=1
Cookie cs[] = request.getCookies();
if(cs==null){
return id;
}
// cookie不为null，但没有bookHistory 1 bookHistory=1
Cookie bookHistoryCookie = null;
for(Cookie c:cs){
if("bookHistory".equals(c.getName())){
bookHistoryCookie = c;
break;
}
}
if(bookHistoryCookie==null){
return id;
}
// bookHistory=1 2 bookHistory=2-1
// bookHistory=1-2 3 bookHistory=3-1-2
// bookHistory=1-2 2 bookHistory=2-1
String value = bookHistoryCookie.getValue();
String ids[] = value.split("\-");
LinkedList<String> list = new LinkedList<String>(Arrays.asList(ids));
if(list.size()<3){
if(list.contains(id)){
list.remove(id);
}
}else{
// bookHistory=1-2-3 4 bookHistory=4-1-2
// bookHistory=1-2-3 2 bookHistory=2-1-3
if(list.contains(id)){
list.remove(id);
}else{
list.removeLast();
}
}
list.addFirst(id);
StringBuffer sb = new StringBuffer();
for(int i=0;i<list.size();i++){
if(i>0){
sb.append("-");
}
sb.append(list.get(i));
}
return sb.toString();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3. 服务器端技术：HttpSession
3.1 HttpSession是一个域对象及HttpSession的原理
void setAttribute(String name,Object value);
Object getAttribute(String name);
void removeAttribute(String name);
String getId()
HttpSession request.getSession();
//演示HttpSession的原理
public class SessionDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String name = request.getParameter("name");
if(name==null){
out.write("请这样访问：http://192.168.33.172:8080/day09_01_HttpSession/servlet/SessionDemo1?name=abc");
return;
}
//得到HttpSession的实例
HttpSession session = request.getSession();
//在创建HttpSession对象的同时，服务器给这个对象分配一个唯一的ID（GUID）
System.out.println("SessionDemo1中HttpSession对象的id："+session.getId());
session.setAttribute("p", name);
out.write("放了。<a href='http://192.168.33.172:8080/day09_01_HttpSession/servlet/SessionDemo2'>去看看</a>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
public class SessionDemo2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
System.out.println("SessionDemo2中HttpSession对象的id："+session.getId());
String v = (String)session.getAttribute("p");
response.getWriter().write(v);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
HttpSession request.getSession(boolean b):
b如果为true，和getSession()完全一样的
b为false，服务器只是查找，找不到不会创建新的，返回null。
HttpSession.invalidate();使HttpSession对象立即失效。
3.2 3个案例
3.2.1 使用Session完成简单的购物功能
使用上边的 book类 和 模拟 bookdb 数据
public class Book implements Serializable
//显示所有可购买的商品，提供购买链接
//提供一个查看购物车的链接
public class ShowAllBooksServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.getSession(); //为了使 url 重写
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//显示所有可购买的商品，提供购买链接
out.write("<h1>本站有以下好书：</h1>");
Map<String, Book> books = BookDB.findAllBooks();
for(Map.Entry<String, Book> me:books.entrySet()){
String url = request.getContextPath()+"/servlet/BuyServlet?id="+me.getKey();
url = response.encodeURL(url);
out.write(me.getValue().getName()+" <a href='"+url+"'>购买</a><br/>");
}
//提供一个查看购物车的链接
String url = request.getContextPath()+"/servlet/ShowCartServlet";
url = response.encodeURL(url);
out.write("<a href='"+url+"'>查看购物车</a>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//把书籍放入购物车
public class BuyServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String id = request.getParameter("id");
Book b = BookDB.findById(id);
//放到HttpSession中》用List来存
HttpSession session = request.getSession();
List<Book> cart = (List<Book>) session.getAttribute("cart");
if(cart==null){
cart = new ArrayList<Book>();
session.setAttribute("cart", cart);
}
//肯定有购物车
cart.add(b);
String url = request.getContextPath()+"/servlet/ShowAllBooksServlet";
url = response.encodeURL(url);
out.write(b.getName()+"已放入您的购物车<a href='"+url+"'>继续购物</a>");
//为学习原理而做
// Cookie c = new Cookie("JSESSIONID", session.getId());
// c.setPath(request.getContextPath());
// c.setMaxAge(Integer.MAX_VALUE);
// response.addCookie(c);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//显示购物车
public class ShowCartServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
HttpSession session = request.getSession();
List<Book> cart = (List<Book>)session.getAttribute("cart");
if(cart==null||cart.size()==0){
out.write("您还没有购买任何商品");
return;
}
out.write("<h1>你购买的商品如下</h1>");
for(Book b:cart){
out.write(b.getName()+"<br/>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3.2.2 完成用户的登录
//user类
public class User {
private String username;
private String password;
private String nickname;
public User(){}
public User(String username, String password, String nickname) {
super();
this.username = username;
this.password = password;
this.nickname = nickname;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getNickname() {
return nickname;
}
public void setNickname(String nickname) {
this.nickname = nickname;
}
}
public class UserDB {
private static List<User> users = new ArrayList<User>();
static{
users.add(new User("wzt", "123", "动感超油"));
}
public static User login(String username,String password){
for(User u:users){
if(u.getUsername().equals(username)&&u.getPassword().equals(password)){
return u;
}
}
return null;
}
}
//模拟主页
public class IndexServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("这是主页");
HttpSession s = request.getSession();
User user = (User)s.getAttribute("user");//获取登录标记
if(user==null){
//说明没有登录
out.write("<a href='"+request.getContextPath()+"/servlet/LoginUIServlet'>登录</a>");
}else{
out.write("欢迎您："+user.getNickname()+"<a href='"+request.getContextPath()+"/servlet/LogoutServlet'>注销</a>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//提供登录界面
public class LoginUIServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("<form action='"+request.getContextPath()+"/servlet/LoginServlet' method='post'>");
out.write("用户名： <input type='text' name='username' /><br/>");
out.write("密码： <input type='password' name='password' /><br/>");
out.write("验证码： <input type='text' name='code' /><img src='"+request.getContextPath()+"/servlet/ImageServlet'/><br/>");
out.write(" <input type='submit' value='登录' /><br/>");
out.write("</form>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//登录检
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String username = request.getParameter("username");
String password = request.getParameter("password");
User user = UserDB.login(username, password);
if(user==null){
out.write("错误的用户或密码,2秒后转向登录界面");
response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
return;
}
HttpSession session = request.getSession();
//验证码是否正确
String code = request.getParameter("code");
String scode = (String) session.getAttribute("code");
if(!code.equals(scode)){
out.write("错误的验证码,2秒后转向登录界面");
response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
return;
}
//登录成功
session.setAttribute("user", user);
out.write("登录成功,2秒后转向主页");
response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/IndexServlet");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
//注销
public class LogoutServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
HttpSession session = request.getSession();
// session.invalidate();//立即失效
session.removeAttribute("user");
out.write("注销成功,2秒后转向主页");
response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/IndexServlet");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
public class ImageServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int width = 120;
int height = 25;
//创建一副内存图像
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//得到画笔
Graphics g = image.getGraphics();
//开始画
//边线
g.setColor(Color.BLUE);
g.drawRect(0, 0, width, height);
//填充背景色
g.setColor(Color.YELLOW);
g.fillRect(1, 1, width-2, height-2);
//话干扰线
g.setColor(Color.GRAY);
Random r = new Random();
for(int i=0;i<9;i++)
g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
//验证码
g.setColor(Color.RED);
g.setFont(new Font("宋体", Font.ITALIC|Font.BOLD, 19));
// String base = "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";
int x = 20;
StringBuffer sb = new StringBuffer();
for(int i=0;i<4;i++){
String num = r.nextInt(10)+"";
sb.append(num);
g.drawString(num, x,20 );
// g.drawString(base.charAt(r.nextInt(base.length()))+"", x, 20);
x+=18;
}
request.getSession().setAttribute("code", sb.toString());
//输出
response.setHeader("Expires", "-1");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
ImageIO.write(image, "jpg", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3.2.3 防止表单的重复提交
//注册页面
public class RegistUIServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//产生一个唯一的ID（GUID就是UUID）
// String token = UUID.randomUUID().toString();
String token = new BigInteger(165, new Random()).toString(36).toUpperCase();//GUID
request.getSession().setAttribute("token", token);
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("<form action='/day09_01_HttpSession/servlet/RegistServlet' method='post'>");
out.write("姓名：<input name='name'/><br/>");
out.write("<input type='hidden' name='token' value='"+token+"'/><br/>");
out.write("<input type='submit' value='保存'/></form>");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
public class RegistServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String name = request.getParameter("name");
// try {
// Thread.sleep(1000);
// } catch (InterruptedException e) {
// e.printStackTrace();
// }//模拟网络慢
String stoken = (String) request.getSession().getAttribute("token");
String ftoken = request.getParameter("token");
if(ftoken.equals(stoken)){
System.out.println(name);
request.getSession().removeAttribute("token");
}else{
out.write("请不要重复提交");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3.3 客户端禁用Cookie后的会话数据的保持
客户端永远不会向服务器端带任何cookie。
解决办法：
方式一：（乌龙）文字提示：请不要禁用您的Cookie
方式二：在访问的地址后面加上JSESSIONID=session的id。
http://localhost:8080/servlet/ServletDemo1 URL重写，必须对网站的所有地址都重写
http://localhost:8080/servlet/ServletDemo1;JSESSIONID=123
response.encodeUrl(String url);自动重写。 对购物车案例 修改了
3.4 HttpSession对象的状态
很多 银行的保护性就是将session 减短了。
public class Book implements Serializable 序列化
4 总结
一、会话概述
1、如同一次电话通话。
2、会话中要解决的问题：多次请求中的数据的保持问题。典型：购物车
二、Cookie
1、属性：
name value path maxAge domain version 等
2、HttpServletResponse.addCookie(Cookie c)
3、HttpServletRequest.getCookies()
4、记住用户名和记住用户的浏览记录
三、HttpSession
1、HttpSession是一个域对象
2、HttpSession的原理（借助Cookie）
3、HttpSession.getSession():先查（按照session对象的ID去查），没有再创建。
4、案例：
简单购物车
用户登录和验证码验证
防止表单的重复提交：从原理上明白
5、客户端禁用了Cookie后的会话数据保持问题
URL重写
6、HttpSession对象的状态变化：钝化和激活。 向HttpSession中存放的对象的类，要实现java.io.Serializable接口
7、浏览器何时会开启一次新的会话。