J2EE进阶之Cookie和Session 十一

梦里梦外; 2024-02-17 23:47 29阅读 0赞

## **Cookie和Session** ##

### Cookie：客户端技术； ###

Cookie是客户端技术，程序把每个用户的数据以cookie的形式写给用户各自的浏览器。当用户使用浏览器再去访问服务器中的web资源时，就会带着各自的数据去。这样，web资源处理的就是用户各自的数据了

### HttpSession：服务器端技术。 ###

Session是服务器端技术，利用这个技术，服务器在运行时可以为每一个用户的浏览器创建一个其独享的HttpSession对象，由于session为用户浏览器独享，所以用户在访问服务器的web资源时，可以把各自的数据放在各自的session中，当用户再去访问服务器中的其它web资源时，其它web资源再从用户各自的session中取出数据为用户服务

### Cookie ###

1、客户端技术  
本地最多存300个cookie，服务器端最多存20个  
举例说明：我们访问后台程序，带过去一些数据，这些数据被存入servletrequest的addcookie方法写入cookei中。

2、Cookie属性：

name：必须的。    
    value：必须的。  
    path：路径。默认值。写cookie的那个程序的uri访问路径 。

![9RazyfU.png][]

domain：域。默认值。写cookie的那个程序所在的网站。  
    domain默认值：localhost  
    maxAge：最大存活时间。默认在浏览器的内存中。设置一个自然整数，单位是秒，这样浏览器就会把cookie信息存到自己的缓存区。  
    清楚cookei值得根本是清除本地的cookie，需要地址一致。如果访问的domain（网站地址）+path（工程的servlet路径）不一致，那么此次范文不会传递cookie过去，也就无法设置cookie。  
    我们可以手动设置cookei的uri地址。比如默认path为/abc/dd/，设置路径为/abc,那么以/abc开头的都能发送cookei.
    version：版本号。
    comment：注释。

#### 记录和显示最近的访问时间，和清除时间 ####

##### 记录 #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 import java.io.PrintWriter;
      5 import java.text.DateFormat;
      6 import java.text.ParseException;
      7 import java.text.SimpleDateFormat;
      8 import java.util.Date;
      9 
     10 import javax.servlet.ServletException;
     11 import javax.servlet.http.Cookie;
     12 import javax.servlet.http.HttpServlet;
     13 import javax.servlet.http.HttpServletRequest;
     14 import javax.servlet.http.HttpServletResponse;
     15 /**
     16  * 记录和显示最近的访问时间：cookie技术
     17  * @author Angus
     18  *
     19  */
     20 public class CookieDemo1 extends HttpServlet {
     21 
     22     public void doGet(HttpServletRequest request, HttpServletResponse response)
     23             throws ServletException, IOException {
     24         response.setContentType("text/html;charset=UTF-8");
     25         PrintWriter out = response.getWriter();
     26         out.write("您上次访问的时间是：<a href='"+request.getContextPath()+"/servlet/CookieDemo2'>清除</a>");
     27         //读取指定的Cookie：lastAccessTime=1010010毫秒
     28         Cookie cs[] = request.getCookies();
     29         for(int i=0;cs!=null&&i<cs.length;i++){
     30             if("lastAccessTime".equals(cs[i].getName())){
     31                 String value = cs[i].getValue();//时间毫秒值
     32                 Date date = new Date(Long.parseLong(value));
     33                 out.write(date.toLocaleString());
     34                 break;
     35             }
     36         }
     37         //向客户端写cookie
     38         Cookie cookie = new Cookie("lastAccessTime", System.currentTimeMillis()+"");
     39         cookie.setMaxAge(Integer.MAX_VALUE);//永久
     40         response.addCookie(cookie);
     41     }
     42 
     43     public void doPost(HttpServletRequest request, HttpServletResponse response)
     44             throws ServletException, IOException {
     45         doGet(request, response);
     46     }
     47 
     48 }

##### 读取和清除 #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 
      5 import javax.servlet.ServletException;
      6 import javax.servlet.http.Cookie;
      7 import javax.servlet.http.HttpServlet;
      8 import javax.servlet.http.HttpServletRequest;
      9 import javax.servlet.http.HttpServletResponse;
     10 //清除最后的访问时间
     11 public class CookieDemo2 extends HttpServlet {
     12 
     13     public void doGet(HttpServletRequest request, HttpServletResponse response)
     14             throws ServletException, IOException {
     15         Cookie cookie = new Cookie("lastAccessTime", "");//必须是同一个Cookie才行。domain+path+name
     16         cookie.setMaxAge(0); //清除时间Cookie
     17         response.addCookie(cookie);//写回去
     18     }
     19 
     20     public void doPost(HttpServletRequest request, HttpServletResponse response)
     21             throws ServletException, IOException {
     22         doGet(request, response);
     23     }
     24 
     25 }

##### 运行效果 #####

![yJKb3vm.jpg][]

#### 记录登录名 ####

##### Servlet处理 #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 import java.io.PrintWriter;
      5 
      6 import javax.servlet.ServletException;
      7 import javax.servlet.http.Cookie;
      8 import javax.servlet.http.HttpServlet;
      9 import javax.servlet.http.HttpServletRequest;
     10 import javax.servlet.http.HttpServletResponse;
     11 
     12 /**
     13  * Servlet implementation class LoginServlet1
     14  */
     15 public class LoginServlet1 extends HttpServlet {
     16 
     17     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     18         
     19         response.setContentType("text/html;charset=UTF-8");
     20         PrintWriter out = response.getWriter();
     21         //验证用户名和密码:  abc---密码cba
     22         String username = request.getParameter("username");
     23         String password = request.getParameter("password");
     24         password = new StringBuffer(password).reverse().toString();
     25         if(!username.equals(password)){
     26             out.write("错误的用户名或密码。2秒后自动转向登录页面");
     27             response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
     28             return;
     29         }
     30         response.getWriter().write("登陆成功");
     31         
     32         //根据是否记住用户名，保存cookie
     33         String remember = request.getParameter("remember");//没有选择，null
     34         Cookie c = new Cookie("loginInfo", username);
     35         c.setPath(request.getContextPath());
     36         if(remember==null){
     37             //没有选择：删除cookie
     38             c.setMaxAge(0);
     39         }else{
     40             //选择：记住cookie
     41             c.setMaxAge(Integer.MAX_VALUE);
     42         }
     43         response.addCookie(c);
     44     }
     45 
     46     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     47         
     48     }
     49 
     50 }

##### UI页面： #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 import java.io.PrintWriter;
      5 
      6 import javax.servlet.ServletException;
      7 import javax.servlet.http.Cookie;
      8 import javax.servlet.http.HttpServlet;
      9 import javax.servlet.http.HttpServletRequest;
     10 import javax.servlet.http.HttpServletResponse;
     11 
     12 /**
     13  * 登录UI
     14  */
     15 public class LoginUIServlet1 extends HttpServlet {
     16 
     17     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     18         response.setContentType("text/html;charset=UTF-8");
     19         PrintWriter writer = response.getWriter();
     20         
     21         //显示已经记住的用户名
     22                 String username = "";
     23                 String checked = "";
     24                 Cookie cs[] = request.getCookies();
     25                 for(int i=0;cs!=null&&i<cs.length;i++){
     26                     if("loginInfo".equals(cs[i].getName())){
     27                         username = cs[i].getValue();
     28                         checked = "checked='checked'";
     29                         break;
     30                     }
     31                 }
     32         //显示登录页面
     33         writer.write("<form action='"+request.getContextPath()+"/LoginServlet1' methond='POST'>");
     34         writer.write("username:<input type='text' name='username' value='"+username+"'/><br/>");
     35         writer.write("password:<input type='text' name='password' value=''/><br/>");
     36         writer.write("<input type='checkbox' name='remember' "+checked+"/>记住用户名<br/>");
     37         writer.write("<input type='submit' value='登陆'/>");
     38         writer.write("</form>");
     39         
     40     }
     41 
     42     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     43         doGet(request, response);
     44     }
     45 
     46 }

### Session ###

#### 原理： ####

１：HttpSession内存中查找谁的ID是这个的HttpSession对象。找到：取出来继续使用。没有找到：创建新的。。。。。

如图：  
![Bt3FnVS.png][]

２：HttpSession session = request.getSession(boolean create);  
create:true。和没有参数的getSession()是一样的。  
create:false。只是查找，找不到返回null。

３配置失效时间：

![3LK3AKc.png][]

Long getLastAccessedTime():返回最近的一次访问时间  
void invalidate():立即失效

#### 用户登录注销 ####

##### LoginUIServlet #####

##### LoginServlet #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 import java.io.PrintWriter;
      5 
      6 import javax.servlet.ServletException;
      7 import javax.servlet.http.HttpServlet;
      8 import javax.servlet.http.HttpServletRequest;
      9 import javax.servlet.http.HttpServletResponse;
     10 
     11 import com.itheima.domain.User;
     12 
     13 public class LoginServlet extends HttpServlet {
     14 
     15     public void doGet(HttpServletRequest request, HttpServletResponse response)
     16             throws ServletException, IOException {
     17         response.setContentType("text/html;charset=UTF-8");
     18         PrintWriter out = response.getWriter();
     19         //验证用户名和密码:  abc---密码cba
     20         String username = request.getParameter("username");
     21         String password = request.getParameter("password");
     22         password = new StringBuffer(password).reverse().toString();
     23         if(!username.equals(password)){
     24             out.write("错误的用户名或密码。2秒后自动转向登录页面");
     25             response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
     26             return;
     27         }
     28         //用户名和密码都正确：向HttpSession中设置标记
     29         User user = new User(username,password,"游客");
     30         request.getSession().setAttribute("user", user);
     31         response.getWriter().write("登陆成功,2秒后转向主页");
     32         response.setHeader("Refresh", "2;URL="+request.getContextPath());
     33     }
     34 
     35     public void doPost(HttpServletRequest request, HttpServletResponse response)
     36             throws ServletException, IOException {
     37         doGet(request, response);
     38     }
     39 
     40 }

##### IndexServlet #####

1 package com.wsj;
      2 
      3 import java.io.IOException;
      4 import java.io.PrintWriter;
      5 
      6 import javax.servlet.ServletException;
      7 import javax.servlet.http.HttpServlet;
      8 import javax.servlet.http.HttpServletRequest;
      9 import javax.servlet.http.HttpServletResponse;
     10 import javax.servlet.http.HttpSession;
     11 
     12 import com.itheima.domain.User;
     13 /**
     14  * 主页
     15  * @author Angus
     16  *
     17  */
     18 public class IndexServlet extends HttpServlet {
     19 
     20     public void doGet(HttpServletRequest request, HttpServletResponse response)
     21             throws ServletException, IOException {
     22         response.setContentType("text/html;charset=UTF-8");
     23         PrintWriter out = response.getWriter();
     24         
     25         HttpSession session = request.getSession();
     26         User user = new User();
     27         
     28         if(user==null){
     29             out.write("<a href='"+request.getContextPath()+"/servlet/LoginUIServlet'>登录</a>");
     30         }else{
     31             out.write("欢迎您："+user.getNickname()+"<a href='"+request.getContextPath()+"/servlet/LoginOutServlet'>注销</a>");
     32         }
     33         out.write("<hr/>这是主页");
     34     }
     35 
     36     public void doPost(HttpServletRequest request, HttpServletResponse response)
     37             throws ServletException, IOException {
     38         doGet(request, response);
     39     }
     40 
     41 }

##### LoginOutServlet #####

#### 利用HttpSession防止表单重复提交 ####

![ytZmnz3.png][]

##### PayUIServlet #####

1 import java.io.IOException;
      2 import java.io.PrintWriter;
      3 import java.util.UUID;
      4 
      5 import javax.servlet.ServletException;
      6 import javax.servlet.http.HttpServlet;
      7 import javax.servlet.http.HttpServletRequest;
      8 import javax.servlet.http.HttpServletResponse;
      9 /**
     10  * 生成唯一的令牌
     11  * @author Angus
     12  *
     13  */
     14 public class PayUIServlet extends HttpServlet {
     15 
     16     public void doGet(HttpServletRequest request, HttpServletResponse response)
     17             throws ServletException, IOException {
     18         response.setContentType("text/html;charset=UTF-8");
     19         PrintWriter out = response.getWriter();
     20         String token = UUID.randomUUID().toString();//唯一  GUID
     21         
     22         request.getSession().setAttribute("token", token);
     23         out.write("<form action='"+request.getContextPath()+"/servlet/PayServlet' method='post'>");
     24         out.write("付款金额：<input type='text' name='money' value='10000'/><br/>");
     25         out.write("<input type='hidden' name='token' value='"+token+"'/><br/>");
     26         out.write("<input type='submit' value='付款'/><br/>");
     27         out.write("</form>");
     28         
     29     }
     30 
     31     public void doPost(HttpServletRequest request, HttpServletResponse response)
     32             throws ServletException, IOException {
     33         doGet(request, response);
     34     }
     35 
     36 }

##### PayServlet #####

1 import java.io.IOException;
      2 import java.io.PrintWriter;
      3 
      4 import javax.servlet.ServletException;
      5 import javax.servlet.http.HttpServlet;
      6 import javax.servlet.http.HttpServletRequest;
      7 import javax.servlet.http.HttpServletResponse;
      8 import javax.servlet.http.HttpSession;
      9 /**
     10  * 
     11  * @author Angus
     12  *
     13  */
     14 public class PayServlet extends HttpServlet {
     15 
     16     public void doGet(HttpServletRequest request, HttpServletResponse response)
     17             throws ServletException, IOException {
     18         response.setContentType("text/html;charset=UTF-8");
     19         PrintWriter out = response.getWriter();
     20         String money = request.getParameter("money");
     21         String formToken = request.getParameter("token");
     22         HttpSession session = request.getSession();
     23         String sessionToken = (String) session.getAttribute("token");
     24         synchronized (PayServlet.class) {
     25             if(formToken.equals(sessionToken)){
     26                 
     27                     System.out.println("支付成功，金额是:" + money);
     28                     session.removeAttribute("token");  //移除后就无法重复提交
     29                 
     30             }else{
     31                 out.write("请不要重复提交");
     32             }
     33         }
     34     }
     35 
     36     public void doPost(HttpServletRequest request, HttpServletResponse response)
     37             throws ServletException, IOException {
     38         doGet(request, response);
     39     }
     40 
     41 }

##### 效果： #####

![3A1asoj.png][]

##### 再次提交 #####

![8scNo6u.jpg][]

#### 客户端禁用Cookie后的会话数据保持 ####

禁用Cookie：浏览器永远不会向服务器端发送Cookie的请求消息头 。  
方式一：主页上提示：为了更好浏览本网站，请不要禁用您的Cookie（很多网站都不做处理。。。）  
方式二：URL重写。 在URL侯拼上 JSESSIONID  
[http://localhost:8080/day10\_05\_shopping/servlet/ShowCartServlet][http_localhost_8080_day10_05_shopping_servlet_ShowCartServlet]  
[http://localhost:8080/day10\_05\_shopping/servlet/ShowCartServlet;JSESSIONID=11111][http_localhost_8080_day10_05_shopping_servlet_ShowCartServlet_JSESSIONID_11111]

特别注意：要重写就必须所有的地址都重写  
response.encodeUrl(String url);自动判断用户是否禁用，没有禁用就不重写。

#### HttpSession对象的状态 ####

![h14zapA.png][]

日后：\#\# javaBean一般情况下都要实现java.io.Serialiazable接口 \#\#，可以避免异常  
偶尔会报个异常：  
![cb6Eq0K.png][]

[9RazyfU.png]: http://i.imgur.com/9RazyfU.png
[yJKb3vm.jpg]: http://i.imgur.com/yJKb3vm.jpg
[Bt3FnVS.png]: http://i.imgur.com/Bt3FnVS.png
[3LK3AKc.png]: http://i.imgur.com/3LK3AKc.png
[ytZmnz3.png]: http://i.imgur.com/ytZmnz3.png
[3A1asoj.png]: http://i.imgur.com/3A1asoj.png
[8scNo6u.jpg]: http://i.imgur.com/8scNo6u.jpg
[http_localhost_8080_day10_05_shopping_servlet_ShowCartServlet]: http://localhost:8080/day10_05_shopping/servlet/ShowCartServlet
[http_localhost_8080_day10_05_shopping_servlet_ShowCartServlet_JSESSIONID_11111]: http://localhost:8080/day10_05_shopping/servlet/ShowCartServlet;JSESSIONID=11111
[h14zapA.png]: http://i.imgur.com/h14zapA.png
[cb6Eq0K.png]: http://i.imgur.com/cb6Eq0K.png