第74节：Java中的Cookie和Session

时间：2023-03-10 03:45:00
第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

第74节：第74节：Java中的Cookie和Session

ServletContext:

什么是ServletContext,有什么用哦，怎么用呢？

启动服务器后，会给每个应用程序创建一个ServletContext,并且这个ServletContext对象只有一个。可以用于获取全局参数，工程下的资源，和存取数据，共享数据。

例子，如何获取全局参数，如何获取工程下的资源，如何进行存取数据，用例子代码进行展示。

getServletContext().getInitParams();和getServletConfig().getInitParams();

getServletContext().getRealPath()

getServletContext().getReasourceAsStream()

InputStream is = getClass().getClassLoader().getReasourceAsStream();

相对路径和绝对路径

getServletContext().setAttribute()

getServletContext().getAttribute()

获取登录成功次数

HttpServletRequest:

请求对象，用于封装客户端提交过来的数据或者信息。

可以获取头信息，提交过来的数据：

`request.getParameter("name"); // dashucoding url连接拼接

中文乱码情况

HttpServletResponse:

响应对象，服务器要返回给客户端的数据

跳转页面：

response.setStatus(302);

response.setHeader("Location","success.html");

文件下载：输出流和输入流的对接

下载中文名字的资源：

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

// index.html

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

	默认servlet去下载<br>

	<a href="download/aa.jpg">aa.jpg</a><br>

	<a href="download/bb.txt">bb.txt</a><br>

	<a href="download/cc.rar">cc.rar</a><br>

	<br>手动下载<br>

	<a href="Demo01?filename=aa.jpg">aa.jpg</a><br>

	<a href="Demo01?filename=bb.txt">bb.txt</a><br>

	<a href="Demo01?filename=cc.rar">cc.rar</a><br>

	<a href="Demo01?filename=达叔.png">达叔.png</a><br>

</body>

</html>
// Demo01.java

package com.dashucoding.servlet;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class Demo01

 */

public class Demo01 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		// 获取要下载的文件名字

		String fileName = request.getParameter("filename");

		// 获取这个文件在tomcat里面的绝对路径地址

		String path = getServletContext().getRealPath("download/"+fileName);

		// 用于用户下载

		response.setHeader("Content-Disposition", "attachment; filename="+fileName);

		// 转化成输入流

		InputStream is = new FileInputStream(path);

		OutputStream os = response.getOutputStream();

		int len = 0;

		byte[] buffer = new byte[1024];

		while( (len = is.read(buffer)) != -1) {

			os.write(buffer, 0, len);

		}

		os.close();

		is.close();

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

浏览器

// Demo01.java

package com.dashucoding.servlet;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URLEncoder;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class Demo01

 */

public class Demo01 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		// 获取要下载的文件名字

		String fileName = request.getParameter("filename");

		// get请求有中文

		//byte[] bytes = fileName.getBytes("ISO-8859-1");

		//new String(bytes, "UTF-8");

		fileName = new String(fileName.getBytes("ISO-8859-1"), "UTF-8");

		System.out.println("fileName="+fileName);

		// 获取这个文件在tomcat里面的绝对路径地址

		String path = getServletContext().getRealPath("download/"+fileName);

		// 对中文的名字进行编码处理

		// 获取来访客户端的类型

		String clientType = request.getHeader("User-Agent");

		if (clientType.contains("Firefox")) {

			fileName = DownLoadUtil.base64EncodeFileName(fileName);

		}else {

			fileName = URLEncoder.encode(fileName, "UTF-8");

		}

		// 用于用户下载

		response.setHeader("Content-Disposition", "attachment; filename="+fileName);

		// 转化成输入流

		InputStream is = new FileInputStream(path);

		OutputStream os = response.getOutputStream();

		int len = 0;

		byte[] buffer = new byte[1024];

		while( (len = is.read(buffer)) != -1) {

			os.write(buffer, 0, len);

		}

		os.close();

		is.close();

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}
// DownLoadUtil

package com.dashucoding.servlet;

import java.io.UnsupportedEncodingException;

import sun.misc.BASE64Encoder;

public class DownLoadUtil {

	public static String base64EncodeFileName(String fileName) {

		BASE64Encoder base64Encoder = new BASE64Encoder();

		try {

			return "=?UTF-8?B?"

					+ new String(base64Encoder.encode(fileName

							.getBytes("UTF-8"))) + "?=";

		} catch (UnsupportedEncodingException e) {

			e.printStackTrace();

			throw new RuntimeException(e);

		}

	}

}

第74节：Java中的Cookie和Session

登录

第74节：Java中的Cookie和Session

// LoginServlet

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LoginServlet

 */

public class LoginServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		// public void setContextType(String type)

		// 设置将发送到客户端的响应的内容类型,如果该响应尚未提交,给定内容类型可能包含字符编码规范,例如

		// text/html;charseet=UTF-8,如果在调用 getWriter之前调用此方法,则只根据给定内容类型设置响应的字符编码

		response.setContentType("text/html;charset=utf-8");

		String userName = request.getParameter("username");

		String password = request.getParameter("password");

		if("admin".equals(userName) && "123".equals(password)) {

			response.getWriter().write("登录成功");

		}else {

			response.getWriter().write("登录失败");

		}

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}
// web

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

  <display-name>RequestRedirctionDemo</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

  <servlet>

    <description></description>

    <display-name>LoginServlet</display-name>

    <servlet-name>LoginServlet</servlet-name>

    <servlet-class>com.dashucoding.servlet.LoginServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>LoginServlet</servlet-name>

    <url-pattern>/login</url-pattern>

  </servlet-mapping>

</web-app>
// login

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

	<form action="login">

		账号: <input type="text"  name="username"/><br>

		密码: <input type="text"  name="password"/><br>

		<input type="submit"  value="登录"/><br>

	</form>

</body>

</html>

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

// LoginServlet

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LoginServlet

 */

public class LoginServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		// public void setContextType(String type)

		// 设置将发送到客户端的响应的内容类型,如果该响应尚未提交,给定内容类型可能包含字符编码规范,例如

		// text/html;charseet=UTF-8,如果在调用 getWriter之前调用此方法,则只根据给定内容类型设置响应的字符编码

		response.setContentType("text/html;charset=utf-8");

		String userName = request.getParameter("username");

		String password = request.getParameter("password");

		if("admin".equals(userName) && "123".equals(password)) {

			// response.getWriter().write("登录成功");

			response.setStatus(302);

			response.setHeader("Location", "login_success.html");

		}else {

			response.getWriter().write("登录失败");

		}

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

第74节：Java中的Cookie和Session

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<h1>登录成功!!!</h1>

</body>

</html>

第74节：Java中的Cookie和Session

重定向

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LoginServlet

 */

public class LoginServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		// public void setContextType(String type)

		// 设置将发送到客户端的响应的内容类型,如果该响应尚未提交,给定内容类型可能包含字符编码规范,例如

		// text/html;charseet=UTF-8,如果在调用 getWriter之前调用此方法,则只根据给定内容类型设置响应的字符编码

		response.setContentType("text/html;charset=utf-8");

		String userName = request.getParameter("username");

		String password = request.getParameter("password");

		if("admin".equals(userName) && "123".equals(password)) {

			// response.getWriter().write("登录成功");

			/*response.setStatus(302);

			response.setHeader("Location", "login_success.html");*/

			// 重定向写法,重新定位方向

			// response.sendRedirect("login_success.html");

			// 请求转发的写法

			request.getRequestDispatcher("login_success.html").forward(request, response);

		}else {

			response.getWriter().write("登录失败");

		}

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

Cookie

用于自动登录,浏览记录等,是服务器给客户端的.

Cookie cookie = new Cookie("a","b");

// 响应

response.addCookie(cookie);

获取Cookie

package com.dashucoding.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;

/**

 * Servlet implementation class Demo01

 */

public class Demo01 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		//Cookie的简单使用。

		//cookie 发送给客户端，并且保存在客户端上的一份小数据

		response.setContentType("text/html;charset=utf-8");

		//发送cookie给客户端

		Cookie cookie = new Cookie("aa", "bb");

		//给响应，添加一个cookie

		response.addCookie(cookie);

		response.getWriter().write("请求成功了...");

		//获取客户端带过来的cookie

		Cookie[] cookies = request.getCookies();

		if(cookies != null){

			for (Cookie c : cookies) {

				String cookieName = c.getName();

				String cookieValue = c.getValue();

				System.out.println(cookieName + " = "+ cookieValue);

			}

		}

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		doGet(request, response);

	}

}

Cookie是一份小数据,是服务器给客户端,存储在客户端上的一份小数据.

http请求是无状态的.

在响应的时候添加Cookie

Cookie cookie = new Cookie("name", "value");

// 添加cookie

response.addCookie(cookie);

在客户端信息里,响应头中多了Set-Cookie

获取客户端带来的Cookie

Cookie[] cookies = request.getCookies();

if(cookies != null){

 for(Cookie c : cookies){

  String cookieName = c.getName();

  String cookieValue = c.getValue();

  System.out.println(cookieName + " = " + cookieValue);

 }

}

cookie过期

public int getMaxAge()

返回以秒为单位指定的cookie的最大生存时间.

public void setMaxAge(int expiry)

设置cookie的最大生存时间,以秒为单位.

如何显示上次登录时间

可以进行判断账号密码,如果上次有登录过,那么显示上次的登录时间.这里分两种情况,获取带过来的cookie进行判断,第一种是没有cookie的,第一次登录,输出登录成功或者失败,然后给客户端添加cookie,new Cookie(),第二种的登录过的,还是要输出登录成功或者是失败,获取以前的cookie.时间戳要重置怎么理解?

package com.dashucoding.servlet;

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;

import com.dashucoding.util.CookieUtil;

/**

 * Servlet implementation class Demo03

 */

public class Demo03 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		response.setContentType("text/html;charset=utf-8");

		String userName = request.getParameter("username");

		String password = request.getParameter("password");

		if("admin".equals(userName) && "123".equals(password)){

			//获取cookie last-name --- >

			Cookie [] cookies = request.getCookies();

			//从数组里面找出我们想要的cookie

			Cookie cookie = CookieUtil.findCookie(cookies, "last");

			//是第一次登录，没有cookie

			if(cookie == null){

				Cookie c = new Cookie("last", System.currentTimeMillis()+"");

				c.setMaxAge(60*60); //一个小时

				response.addCookie(c);

				response.getWriter().write("欢迎您, "+userName);

			}else{

				//1. 去以前的cookie第二次登录，有cookie

				long lastVisitTime = Long.parseLong(cookie.getValue());

				//2. 输出到界面，

				response.getWriter().write("欢迎您, "+userName +",上次来访时间是："+new Date(lastVisitTime));

				//3. 重置登录的时间

				cookie.setValue(System.currentTimeMillis()+"");

				response.addCookie(cookie);

			}

		}else{

			response.getWriter().write("登陆失败 ");

		}

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		doGet(request, response);

	}

}

如何显示商品浏览记录

获取提交过来的id,把id放入到cookie里,跳转界面.

servlet?id=1;

servlet?id=2;

获取cookie 1

1#2

setValue("1#2");

jsp

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

// index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

    pageEncoding="ISO-8859-1"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

 <br>---------1------------<br>

 <%! int a = 123; %>

 <br>---------2------------<br>

 <% int b = 123456; %>

 <br>---------3------------<br>

 <%=a %><br>

 <%=b %>

</body>

</html>

浏览记录

package com.dashucoding.util;

import javax.servlet.http.Cookie;

public class CookieUtil {

	/**

	 * 从一个cookie数组中找到具体我们想要的cookie对象

	 * @param cookies

	 * @param name

	 * @return

	 */

	public static Cookie findCookie(Cookie[] cookies , String name){

		if(cookies != null){

			for (Cookie cookie : cookies) {

				if(name.equals(cookie.getName())){

					return cookie;

				}

			}

		}

		return null;

	}

}
				<!-- 显示浏览记录 -->

				<%

				Cookie[] cookies = request.getCookies();

				Cookie cookie = CookieUtil.findCookie(cookies, "history");

				 // 如果cookie是空,表明没有浏览商品

				 if(cookie == null){

				%>

				 <h2> 您还没有浏览任何商品! </h2>

				<%

				}else{

					// 不是空,表明有浏览记录

					String[] ids = cookie.getValue().split("#");

					for(String id : ids){

				%>

				<li style="width: 150px;height: 216;text-align: center;"><img src="products/1/cs1000<%=id %>.jpg" width="130px" height="130px" /></li>

				<%

					}

				}

				%>
package com.dashucoding.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;

import com.dashucoding.util.CookieUtil;

public class ProductInfoServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		String id = request.getParameter("id");

		Cookie[] cookies = request.getCookies();

		Cookie cookie = CookieUtil.findCookie(cookies, "history");

		if (cookie==null) {

			Cookie cook = new Cookie("history", id);

			cook.setMaxAge(60*60*24*7);

			response.addCookie(cook);

		}else{

			String id2 = cookie.getValue();

			cookie.setValue(id+"#"+id2);

			cookie.setMaxAge(60*60*24*7);

			response.addCookie(cookie);

		}

		response.sendRedirect("product_info.htm");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		doGet(request, response);

	}

}

清除浏览记录

清除cookie

package com.dashucoding.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;

/**

 * Servlet implementation class ClearHistory

 */

public class ClearHistory extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		// 清除cookie

		Cookie c = new Cookie("history", "");

		c.setMaxAge(0);

//		c.setPath("/demo1");

		response.addCookie(c);

		response.sendRedirect("product_list.jsp");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		doGet(request, response);

	}

}

获取cookie,添加cookie

request.getCookie();

response.addCookie();

Cookie分类

cookie.setMaxAge(0); // 删除

cookie.setMaxAge(100); // 100秒

Cloneable

创建一个cookie,cookie是servlet发送到web浏览器中的少量信息,这些信息是由浏览器保存,然后发送回到服务器中.

cookie的值是唯一标识客户端的,可以用于cookie会话管理.一个cookie拥有一个名,值,可以有一些可选属性.但又cookie也存在一些问题.浏览器支持每个web服务器又20个cookie,共有300个cookie,每个限制在4KB.

安全隐患,大小与个数限制.

Session

会话,Session是基于Cookie的一种会话机制.Cookie是服务器返回一部分小数据在客户端,存放在客户端上.

Session是把数据存放在服务端.

interface httpsession

public interface httpSession

常用的方法

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

/**

 * Servlet implementation class Demo01

 */

public class Demo01 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		HttpSession session = request.getSession();

		// 得到会话ID

		session.getId();

		// 存值

		session.setAttribute(name, value);

		// 取值

		session.getAttribute(name);

		// 移植

		session.removeAttribute(name);

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

// web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

  <display-name>SessionDemo02</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

  <servlet>

    <description></description>

    <display-name>LoginServlet</display-name>

    <servlet-name>LoginServlet</servlet-name>

    <servlet-class>com.dashucoding.servlet.LoginServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>LoginServlet</servlet-name>

    <url-pattern>/login</url-pattern>

  </servlet-mapping>

</web-app>
// LoginServlet

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LoginServlet

 */

public class LoginServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		response.setContentType("text/html;charset=utf-8");

		response.getWriter().write("收到请求了");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}
// login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

	<form action="login">

		账号: <input type="text"  name="username"/><br>

		密码: <input type="text"  name="password"/><br>

		<input type="submit"  value="登录"/><br>

	</form>

</body>

</html>

session创建与销毁

创建 request.getSession();

销毁 Redis session 存放在服务器内存中的数据

session关闭服务器销毁

session会话时间过期
// 可以改的 conf\web.xml 有效期30分钟

<session-config>

 <session-timeout>30</session-timeout>

</session-config>
package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LoginServlet

 */

public class LoginServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		response.setContentType("text/html;charset=utf-8");

		String sessionid = request.getSession().getId();

		System.out.println("sessionid="+sessionid);

		// cookid id -> sessionid

		response.getWriter().write("收到请求了");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}

session分析

商品列表添加商品,点击商品添加到购物车,到servlet.

获取点击商品标识id,存储到购物车,跳转界面.

判断购物车是否有商品,有数量加1,没有数量等于1.

购物车

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

package com.dashucoding.servlet;

import java.io.IOException;

import java.util.LinkedHashMap;

import java.util.Map;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class CarServlet

 */

public class CarServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		response.setContentType("text/html;charset=utf-8");

		// 获取添加到购物车的商品id

		int id = Integer.parseInt(request.getParameter("id"));

		// cat dog big pig

		String [] names = {"cat","dog","big","pig"};

		// 取到id对应商品

		String name = names[id];

		// 获取购物车存放东西的session

		// 把一个map 对象存放到session里面去,保证只有一次

		Map<String, Integer> map = (Map<String, Integer>) request.getSession().getAttribute("cat");

		if(map == null) {

			// value -> map

			map = new LinkedHashMap<String, Integer>();

			request.getSession().setAttribute("cat", map);

		}

		// 判断购物车里有没有该商品

		if(map.containsKey(name)) {

			// 在原来基础上 +1

			map.put(name, map.get(name)+1);

		}else {

			map.put(name, 1);

		}

		response.getWriter().write("<a href='product_list.jsp'><h2>继续购物</h2></a>");

		response.getWriter().write("<a href='cart.jsp'><h2>去购物车结算</h2></a>");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}
<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

 <a href="CarServlet?id=0"><h2>cat</h2></a><br>

 <a href="CarServlet?id=1"><h2>dog</h2></a><br>

 <a href="CarServlet?id=2"><h2>big</h2></a><br>

 <a href="CarServlet?id=3"><h2>pig</h2></a><br>

</body>

</html>

第74节：Java中的Cookie和Session

第74节：Java中的Cookie和Session

// cart.jsp

<%@page import="java.util.Map"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

 您的购物车商品如下:

 <%

  // 获取到map

  Map<String,Integer> map = (Map<String,Integer>)session.getAttribute("cat");

  // 遍历

  if(map != null){

	  for(String key : map.keySet()){

		  int value = map.get(key);

		  // key:商品名称 value:商品名称

		  // <h3>名称： 数量: </h3>

  %>

        <h3>名称: <%=key %> 数量: <%=value %></h3><br>

  <%

	  }

  }

  %>

</body>

</html>

第74节：Java中的Cookie和Session

package com.dashucoding.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

/**

 * Servlet implementation class ClearCartServlet

 */

public class ClearCartServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		HttpSession session = request.getSession();

		// cat购物车

		session.removeAttribute("cat");

		response.sendRedirect("cart.jsp");

	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		// TODO Auto-generated method stub

		doGet(request, response);

	}

}
<%@page import="java.util.Map"%>

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

 您的购物车商品如下:

 <%

  // 获取到map

  Map<String,Integer> map = (Map<String,Integer>)session.getAttribute("cat");

  // 遍历

  if(map != null){

	  for(String key : map.keySet()){

		  int value = map.get(key);

		  // key:商品名称 value:商品名称

		  // <h3>名称： 数量: </h3>

  %>

        <h3>名称: <%=key %> 数量: <%=value %></h3><br>

  <%

	  }

  }

  %>

  <a href="ClearCartServlet"><h4>清空购物车</h4></a>

</body>

</html>

第74节：Java中的Cookie和Session

public void invalidate()

使用,会话无效,取消对任何绑定到它的对象.

// 强制干掉会话

// session.invalidate();

小结

cookie和session

Cookie

获取上一次访问时间,获取浏览记录,数据存放在客户端

Session

会话技术,数据存放在服务端

setAttribute 存放数据

getAttribute 取数据

removeAttribute 移除

getSessionId() 获取会话id

invalidate() 让会话失效
response.addCookie(new Cookie())

request.getSession 创建

如果看了觉得不错

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