第74節：Java中的Cookie和Session

時間 2019-12-04

標籤 java cookie session 欄目 Java 简体版

原文原文鏈接

第74節：第74節：Java中的Cookie和Sessionhtml

`ServletContext`:

什麼是ServletContext,有什麼用哦，怎麼用呢？java

啓動服務器後，會給每一個應用程序建立一個ServletContext,而且這個ServletContext對象只有一個。能夠用於獲取全局參數，工程下的資源，和存取數據，共享數據。web

例子，如何獲取全局參數，如何獲取工程下的資源，如何進行存取數據，用例子代碼進行展現。數組

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

getServletContext().getRealPath() getServletContext().getReasourceAsStream()tomcat

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

相對路徑和絕對路徑bash

getServletContext().setAttribute()服務器

getServletContext().getAttribute()cookie

獲取登陸成功次數

`HttpServletRequest`:

請求對象，用於封裝客戶端提交過來的數據或者信息。能夠獲取頭信息，提交過來的數據： `request.getParameter("name"); // dashucoding url鏈接拼接

中文亂碼狀況

`HttpServletResponse`:

響應對象，服務器要返回給客戶端的數據

跳轉頁面： response.setStatus(302);

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

文件下載：輸出流和輸入流的對接

下載中文名字的資源：

// index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

	默認servlet去下載<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>手動下載<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=達叔.png">達叔.png</a><br>
</body>
</html>
複製代碼

// 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
		// 獲取要下載的文件名字
		String fileName = request.getParameter("filename");
		// 獲取這個文件在tomcat裏面的絕對路徑地址
		String path = getServletContext().getRealPath("download/"+fileName);
		
		// 用於用戶下載
		response.setHeader("Content-Disposition", "attachment; filename="+fileName);
		
		// 轉化成輸入流
		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);
	}

}
複製代碼

瀏覽器

// 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
		// 獲取要下載的文件名字
		String fileName = request.getParameter("filename");
		
		// get請求有中文
		//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);
		
		// 獲取這個文件在tomcat裏面的絕對路徑地址
		String path = getServletContext().getRealPath("download/"+fileName);
		
		// 對中文的名字進行編碼處理
		// 獲取來訪客戶端的類型
		String clientType = request.getHeader("User-Agent");
		
		if (clientType.contains("Firefox")) {
			fileName = DownLoadUtil.base64EncodeFileName(fileName);
		}else {
			fileName = URLEncoder.encode(fileName, "UTF-8");
		}
		
		// 用於用戶下載
		response.setHeader("Content-Disposition", "attachment; filename="+fileName);
		
		// 轉化成輸入流
		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);
	}

}
複製代碼

// 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);
		}
	}
}
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登陸

// 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)
		// 設置將發送到客戶端的響應的內容類型,若是該響應還沒有提交,給定內容類型可能包含字符編碼規範,例如
		// text/html;charseet=UTF-8,若是在調用 getWriter以前調用此方法,則只根據給定內容類型設置響應的字符編碼
		
		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("登陸成功");
		}else {
			response.getWriter().write("登陸失敗");
		}
		
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
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// 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>
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// login
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

	<form action="login">
		帳號: <input type="text"  name="username"/><br>
		密碼: <input type="text"  name="password"/><br>
		<input type="submit"  value="登陸"/><br>
	</form>
</body>
</html>
複製代碼

// 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)
		// 設置將發送到客戶端的響應的內容類型,若是該響應還沒有提交,給定內容類型可能包含字符編碼規範,例如
		// text/html;charseet=UTF-8,若是在調用 getWriter以前調用此方法,則只根據給定內容類型設置響應的字符編碼
		
		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("登陸成功");
			response.setStatus(302);
			response.setHeader("Location", "login_success.html");
		}else {
			response.getWriter().write("登陸失敗");
		}
		
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
複製代碼

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>登陸成功!!!</h1>
</body>
</html>
複製代碼

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)
		// 設置將發送到客戶端的響應的內容類型,若是該響應還沒有提交,給定內容類型可能包含字符編碼規範,例如
		// text/html;charseet=UTF-8,若是在調用 getWriter以前調用此方法,則只根據給定內容類型設置響應的字符編碼
		
		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("登陸成功");
			/*response.setStatus(302);
			response.setHeader("Location", "login_success.html");*/
			
			// 重定向寫法,從新定位方向
			// response.sendRedirect("login_success.html");
			
			// 請求轉發的寫法
			request.getRequestDispatcher("login_success.html").forward(request, response);
			
		}else {
			response.getWriter().write("登陸失敗");
		}
		
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
複製代碼

`Cookie`

用於自動登陸,瀏覽記錄等,是服務器給客戶端的.

Cookie cookie = new Cookie("a","b");
// 響應
response.addCookie(cookie);
複製代碼

獲取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的簡單使用。
		
		//cookie 發送給客戶端，而且保存在客戶端上的一份小數據
		
		response.setContentType("text/html;charset=utf-8");
		
		//發送cookie給客戶端
		Cookie cookie = new Cookie("aa", "bb");
		//給響應，添加一個cookie
		response.addCookie(cookie);
		response.getWriter().write("請求成功了...");
		
		
		
		//獲取客戶端帶過來的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);
	}


}
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Cookie是一份小數據,是服務器給客戶端,存儲在客戶端上的一份小數據.

http請求是無狀態的.

在響應的時候添加Cookie

Cookie cookie = new Cookie("name", "value");
// 添加cookie
response.addCookie(cookie);
複製代碼

在客戶端信息裏,響應頭中多了Set-Cookie

獲取客戶端帶來的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);
 }
}
複製代碼

cookie過時

public int getMaxAge() 返回以秒爲單位指定的cookie的最大生存時間.

public void setMaxAge(int expiry) 設置cookie的最大生存時間,以秒爲單位.

如何顯示上次登陸時間

能夠進行判斷帳號密碼,若是上次有登陸過,那麼顯示上次的登陸時間.這裏分兩種狀況,獲取帶過來的cookie進行判斷,第一種是沒有cookie的,第一次登陸,輸出登陸成功或者失敗,而後給客戶端添加cookie,new Cookie(),第二種的登陸過的,仍是要輸出登陸成功或者是失敗,獲取之前的cookie.時間戳要重置怎麼理解?

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)){
			//獲取cookie last-name --- >
			Cookie [] cookies = request.getCookies();
			
			//從數組裏面找出咱們想要的cookie
			Cookie cookie = CookieUtil.findCookie(cookies, "last");
			
			//是第一次登陸，沒有cookie
			if(cookie == null){
				
				Cookie c = new Cookie("last", System.currentTimeMillis()+"");
				c.setMaxAge(60*60); //一個小時
				response.addCookie(c);
				
				response.getWriter().write("歡迎您, "+userName);
				
			}else{
				//1. 去之前的cookie第二次登陸，有cookie
				long lastVisitTime = Long.parseLong(cookie.getValue());
				
				//2. 輸出到界面，
				response.getWriter().write("歡迎您, "+userName +",上次來訪時間是："+new Date(lastVisitTime));
				
				
				//3. 重置登陸的時間
				cookie.setValue(System.currentTimeMillis()+"");
				response.addCookie(cookie);
			}
		}else{
			response.getWriter().write("登錄失敗 ");
		}
	
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}
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如何顯示商品瀏覽記錄

獲取提交過來的id,把id放入到cookie裏,跳轉界面.

servlet?id=1;
servlet?id=2;
獲取cookie 1
1#2
setValue("1#2");
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jsp

// 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>
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瀏覽記錄

package com.dashucoding.util;

import javax.servlet.http.Cookie;

public class CookieUtil {
	/**
	 * 從一個cookie數組中找到具體咱們想要的cookie對象
	 * @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;
	}
}
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<!-- 顯示瀏覽記錄 -->
				<%
				Cookie[] cookies = request.getCookies();
				Cookie cookie = CookieUtil.findCookie(cookies, "history");
				 // 若是cookie是空,代表沒有瀏覽商品
				 if(cookie == null){
				%>
				 <h2> 您尚未瀏覽任何商品! </h2>
				<%
				}else{
					// 不是空,代表有瀏覽記錄
					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>
				<%
					}
				}
				%>
複製代碼

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);
	}
}
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清除瀏覽記錄

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);
	}

}
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獲取cookie,添加cookie

request.getCookie();
response.addCookie();
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Cookie分類

cookie.setMaxAge(0); // 刪除
cookie.setMaxAge(100); // 100秒
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Cloneable

建立一個cookie,cookie是servlet發送到web瀏覽器中的少許信息,這些信息是由瀏覽器保存,而後發送回到服務器中.

cookie的值是惟一標識客戶端的,能夠用於cookie會話管理.一個cookie擁有一個名,值,能夠有一些可選屬性.但又cookie也存在一些問題.瀏覽器支持每一個web服務器又20個cookie,共有300個cookie,每一個限制在4KB.

安全隱患,大小與個數限制.

`Session`

會話,Session是基於Cookie的一種會話機制.Cookie是服務器返回一部分小數據在客戶端,存放在客戶端上.

Session是把數據存放在服務端.

interface httpsession

public interface httpSession
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經常使用的方法

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();
		// 獲得會話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);
	}

}
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// 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>
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// 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("收到請求了");
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
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// 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">
		帳號: <input type="text"  name="username"/><br>
		密碼: <input type="text"  name="password"/><br>
		<input type="submit"  value="登陸"/><br>
	</form>
</body>
</html>
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session建立與銷燬

建立 request.getSession();
銷燬 Redis session 存放在服務器內存中的數據
session關閉服務器銷燬
session會話時間過時
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// 能夠改的 conf\web.xml 有效期30分鐘
<session-config>
 <session-timeout>30</session-timeout>
</session-config>
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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("收到請求了");
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
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session分析

商品列表添加商品,點擊商品添加到購物車,到servlet.

獲取點擊商品標識id,存儲到購物車,跳轉界面.

判斷購物車是否有商品,有數量加1,沒有數量等於1.

購物車

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");
		// 獲取添加到購物車的商品id
		int id = Integer.parseInt(request.getParameter("id"));
		// cat dog big pig
		String [] names = {"cat","dog","big","pig"};
		// 取到id對應商品
		
		String name = names[id];
		
		// 獲取購物車存放東西的session
		// 把一個map 對象存放到session裏面去,保證只有一次
		
		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);
		}
		
		// 判斷購物車裏有沒有該商品
		if(map.containsKey(name)) {
			// 在原來基礎上 +1
			map.put(name, map.get(name)+1);
		}else {
			map.put(name, 1);
		}
		
		response.getWriter().write("<a href='product_list.jsp'><h2>繼續購物</h2></a>");
		response.getWriter().write("<a href='cart.jsp'><h2>去購物車結算</h2></a>");
	}


	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
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<%@ 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>
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// 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>
 您的購物車商品以下:
 <%
  // 獲取到map
  Map<String,Integer> map = (Map<String,Integer>)session.getAttribute("cat");
  // 遍歷
  if(map != null){
	  for(String key : map.keySet()){
		  int value = map.get(key);
		  // key:商品名稱 value:商品名稱
		  // <h3>名稱： 數量: </h3>
  %>
        <h3>名稱: <%=key %> 數量: <%=value %></h3><br>
  <%
	  }
  }
  %>
</body>
</html>
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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購物車
		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);
	}

}
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<%@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>
 您的購物車商品以下:
 <%
  // 獲取到map
  Map<String,Integer> map = (Map<String,Integer>)session.getAttribute("cat");
  // 遍歷
  if(map != null){
	  for(String key : map.keySet()){
		  int value = map.get(key);
		  // key:商品名稱 value:商品名稱
		  // <h3>名稱： 數量: </h3>
  %>
        <h3>名稱: <%=key %> 數量: <%=value %></h3><br>
  <%
	  }
  }
  %>
  <a href="ClearCartServlet"><h4>清空購物車</h4></a>
</body>
</html>
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public void invalidate()
使用,會話無效,取消對任何綁定到它的對象.
// 強制幹掉會話
// session.invalidate();
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小結

cookie和session
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Cookie 獲取上一次訪問時間,獲取瀏覽記錄,數據存放在客戶端

Session 會話技術,數據存放在服務端

setAttribute 存放數據
getAttribute 取數據
removeAttribute 移除
getSessionId() 獲取會話id
invalidate() 讓會話失效
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response.addCookie(new Cookie())
request.getSession 建立
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若是看了以爲不錯

點贊！轉發！

達叔小生：日後餘生，惟獨有你 You and me, we are family ! 90後帥氣小夥，良好的開發習慣；獨立思考的能力；主動而且善於溝通簡書博客：達叔小生 www.jianshu.com/u/c785ece60…

結語

下面我將繼續對其餘知識深刻講解，有興趣能夠繼續關注
小禮物走一走 or 點贊

相關標籤/搜索

cookie&session&localstorage

每日一句

每一个你不满意的现在，都有一个你没有努力的曾经。

第74節：Java中的Cookie和Session

ServletContext:

HttpServletRequest:

HttpServletResponse:

Cookie

Session

小結

結語

`ServletContext`:

`HttpServletRequest`:

`HttpServletResponse`:

`Cookie`

`Session`