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java中的Cookie是什么_第74节：Java中的Cookie和Session

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第74節(jié)：第74節(jié)：Java中的Cookie和Session

ServletContext:

什么是ServletContext,有什么用哦，怎么用呢？

啟動(dòng)服務(wù)器后，會(huì)給每個(gè)應(yīng)用程序創(chuàng)建一個(gè)ServletContext,并且這個(gè)ServletContext對(duì)象只有一個(gè)。可以用于獲取全局參數(shù)，工程下的資源，和存取數(shù)據(jù)，共享數(shù)據(jù)。

例子，如何獲取全局參數(shù)，如何獲取工程下的資源，如何進(jìn)行存取數(shù)據(jù)，用例子代碼進(jìn)行展示。

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

getServletContext().getRealPath()

getServletContext().getReasourceAsStream()

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

相對(duì)路徑和絕對(duì)路徑

getServletContext().setAttribute()

getServletContext().getAttribute()

獲取登錄成功次數(shù)

HttpServletRequest:

請(qǐng)求對(duì)象，用于封裝客戶端提交過(guò)來(lái)的數(shù)據(jù)或者信息。

可以獲取頭信息，提交過(guò)來(lái)的數(shù)據(jù)：

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

中文亂碼情況

HttpServletResponse:

響應(yīng)對(duì)象，服務(wù)器要返回給客戶端的數(shù)據(jù)

跳轉(zhuǎn)頁(yè)面：

response.setStatus(302);

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

文件下載：輸出流和輸入流的對(duì)接

下載中文名字的資源：

// index.html

Insert title here

默認(rèn)servlet去下載

aa.jpg

bb.txt

cc.rar

手動(dòng)下載

aa.jpg

bb.txt

cc.rar

達(dá)叔.png

// 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(gè)文件在tomcat里面的絕對(duì)路徑地址

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

// 用于用戶下載

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

// 轉(zhuǎn)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);

}

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(qǐng)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(gè)文件在tomcat里面的絕對(duì)路徑地址

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

// 對(duì)中文的名字進(jìn)行編碼處理

// 獲取來(lái)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");

}

// 用于用戶下載

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

// 轉(zhuǎn)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);

}

// 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);

}

登錄

// 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(shè)置將發(fā)送到客戶端的響應(yīng)的內(nèi)容類型,如果該響應(yīng)尚未提交,給定內(nèi)容類型可能包含字符編碼規(guī)范,例如

// text/html;charseet=UTF-8,如果在調(diào)用 getWriter之前調(diào)用此方法,則只根據(jù)給定內(nèi)容類型設(shè)置響應(yīng)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("登錄成功");

}else {

response.getWriter().write("登錄失敗");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

// web

RequestRedirctionDemo

index.html

index.htm

index.jsp

default.html

default.htm

default.jsp

LoginServlet

com.dashucoding.servlet.LoginServlet

LoginServlet

/login

// login

Insert title here

賬號(hào):

密碼:

// 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(shè)置將發(fā)送到客戶端的響應(yīng)的內(nèi)容類型,如果該響應(yīng)尚未提交,給定內(nèi)容類型可能包含字符編碼規(guī)范,例如

// text/html;charseet=UTF-8,如果在調(diào)用 getWriter之前調(diào)用此方法,則只根據(jù)給定內(nèi)容類型設(shè)置響應(yīng)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("登錄成功");

response.setStatus(302);

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

}else {

response.getWriter().write("登錄失敗");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

Insert title here

登錄成功!!!

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(shè)置將發(fā)送到客戶端的響應(yīng)的內(nèi)容類型,如果該響應(yīng)尚未提交,給定內(nèi)容類型可能包含字符編碼規(guī)范,例如

// text/html;charseet=UTF-8,如果在調(diào)用 getWriter之前調(diào)用此方法,則只根據(jù)給定內(nèi)容類型設(shè)置響應(yīng)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("登錄成功");

/*response.setStatus(302);

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

// 重定向?qū)懛?重新定位方向

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

// 請(qǐng)求轉(zhuǎn)發(fā)的寫(xiě)法

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

}else {

response.getWriter().write("登錄失敗");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

用于自動(dòng)登錄,瀏覽記錄等,是服務(wù)器給客戶端的.

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

// 響應(yīng)

response.addCookie(cookie);

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(jiǎn)單使用。

//cookie 發(fā)送給客戶端，并且保存在客戶端上的一份小數(shù)據(jù)

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

//發(fā)送cookie給客戶端

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

//給響應(yīng)，添加一個(gè)cookie

response.addCookie(cookie);

response.getWriter().write("請(qǐng)求成功了...");

//獲取客戶端帶過(guò)來(lái)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是一份小數(shù)據(jù),是服務(wù)器給客戶端,存儲(chǔ)在客戶端上的一份小數(shù)據(jù).

http請(qǐng)求是無(wú)狀態(tài)的.

在響應(yīng)的時(shí)候添加Cookie

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

// 添加cookie

response.addCookie(cookie);

在客戶端信息里,響應(yīng)頭中多了Set-Cookie

獲取客戶端帶來(lái)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過(guò)期

public int getMaxAge()

返回以秒為單位指定的cookie的最大生存時(shí)間.

public void setMaxAge(int expiry)

設(shè)置cookie的最大生存時(shí)間,以秒為單位.

如何顯示上次登錄時(shí)間

可以進(jìn)行判斷賬號(hào)密碼,如果上次有登錄過(guò),那么顯示上次的登錄時(shí)間.這里分兩種情況,獲取帶過(guò)來(lái)的cookie進(jìn)行判斷,第一種是沒(méi)有cookie的,第一次登錄,輸出登錄成功或者失敗,然后給客戶端添加cookie,new Cookie(),第二種的登錄過(guò)的,還是要輸出登錄成功或者是失敗,獲取以前的cookie.時(shí)間戳要重置怎么理解?

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)){

//獲取cookie last-name --- >

Cookie [] cookies = request.getCookies();

//從數(shù)組里面找出我們想要的cookie

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

//是第一次登錄，沒(méi)有cookie

if(cookie == null){

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

c.setMaxAge(60*60); //一個(gè)小時(shí)

response.addCookie(c);

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

}else{

//1. 去以前的cookie第二次登錄，有cookie

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

//2. 輸出到界面，

response.getWriter().write("歡迎您, "+userName +",上次來(lái)訪時(shí)間是："+new Date(lastVisitTime));

//3. 重置登錄的時(shí)間

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

response.addCookie(cookie);

}

}else{

response.getWriter().write("登陸失敗 ");

}

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

doGet(request, response);

}

如何顯示商品瀏覽記錄

獲取提交過(guò)來(lái)的id,把id放入到cookie里,跳轉(zhuǎn)界面.

servlet?id=1;

servlet?id=2;

獲取cookie 1

1#2

setValue("1#2");

jsp

// index.jsp

pageEncoding="ISO-8859-1"%>

Insert title here

---------1------------

---------2------------

---------3------------

瀏覽記錄

package com.dashucoding.util;

import javax.servlet.http.Cookie;

public class CookieUtil {

/**

* 從一個(gè)cookie數(shù)組中找到具體我們想要的cookie對(duì)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;

}

Cookie[] cookies = request.getCookies();

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

// 如果cookie是空,表明沒(méi)有瀏覽商品

if(cookie == null){

您還沒(méi)有瀏覽任何商品!

}else{

// 不是空,表明有瀏覽記錄

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

for(String id : ids){

}

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);

}

獲取cookie,添加cookie

request.getCookie();

response.addCookie();

Cookie分類

cookie.setMaxAge(0); // 刪除

cookie.setMaxAge(100); // 100秒

Cloneable

創(chuàng)建一個(gè)cookie,cookie是servlet發(fā)送到web瀏覽器中的少量信息,這些信息是由瀏覽器保存,然后發(fā)送回到服務(wù)器中.

cookie的值是唯一標(biāo)識(shí)客戶端的,可以用于cookie會(huì)話管理.一個(gè)cookie擁有一個(gè)名,值,可以有一些可選屬性.但又cookie也存在一些問(wèn)題.瀏覽器支持每個(gè)web服務(wù)器又20個(gè)cookie,共有300個(gè)cookie,每個(gè)限制在4KB.

安全隱患,大小與個(gè)數(shù)限制.

Session

會(huì)話,Session是基于Cookie的一種會(huì)話機(jī)制.Cookie是服務(wù)器返回一部分小數(shù)據(jù)在客戶端,存放在客戶端上.

Session是把數(shù)據(jù)存放在服務(wù)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();

// 得到會(huì)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);

}

// web.xml

SessionDemo02

index.html

index.htm

index.jsp

default.html

default.htm

default.jsp

LoginServlet

com.dashucoding.servlet.LoginServlet

LoginServlet

/login

// 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(qǐng)求了");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

// login.jsp

pageEncoding="UTF-8"%>

Insert title here

賬號(hào):

密碼:

session創(chuàng)建與銷毀

創(chuàng)建 request.getSession();

銷毀 Redis session 存放在服務(wù)器內(nèi)存中的數(shù)據(jù)

session關(guān)閉服務(wù)器銷毀

session會(huì)話時(shí)間過(guò)期

// 可以改的 conf\web.xml 有效期30分鐘

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(qǐng)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,點(diǎn)擊商品添加到購(gòu)物車,到servlet.

獲取點(diǎn)擊商品標(biāo)識(shí)id,存儲(chǔ)到購(gòu)物車,跳轉(zhuǎn)界面.

判斷購(gòu)物車是否有商品,有數(shù)量加1,沒(méi)有數(shù)量等于1.

購(gòu)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(gòu)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(duì)應(yīng)商品

String name = names[id];

// 獲取購(gòu)物車存放東西的session

// 把一個(gè)map 對(duì)象存放到session里面去,保證只有一次

Map map = (Map) request.getSession().getAttribute("cat");

if(map == null) {

// value -> map

map = new LinkedHashMap();

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

}

// 判斷購(gòu)物車?yán)镉袥](méi)有該商品

if(map.containsKey(name)) {

// 在原來(lái)基礎(chǔ)上 +1

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

}else {

map.put(name, 1);

}

response.getWriter().write("

繼續(xù)購(gòu)物

");

response.getWriter().write("

去購(gòu)物車結(jié)算

");

}

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

// TODO Auto-generated method stub

doGet(request, response);

}

pageEncoding="UTF-8"%>

Insert title here

cat

dog

big

pig

// cart.jsp

pageEncoding="UTF-8"%>

Insert title here

您的購(gòu)物車商品如下:

// 獲取到map

Map map = (Map)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

名稱：數(shù)量:

名稱: 數(shù)量:

}

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(gòu)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);

}

pageEncoding="UTF-8"%>

Insert title here

您的購(gòu)物車商品如下:

// 獲取到map

Map map = (Map)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

名稱：數(shù)量:

名稱: 數(shù)量:

}

清空購(gòu)物車

public void invalidate()

使用,會(huì)話無(wú)效,取消對(duì)任何綁定到它的對(duì)象.

// 強(qiáng)制干掉會(huì)話

// session.invalidate();

小結(jié)

cookie和session

獲取上一次訪問(wèn)時(shí)間,獲取瀏覽記錄,數(shù)據(jù)存放在客戶端

Session

會(huì)話技術(shù),數(shù)據(jù)存放在服務(wù)端

setAttribute 存放數(shù)據(jù)

getAttribute 取數(shù)據(jù)

removeAttribute 移除

getSessionId() 獲取會(huì)話id

invalidate() 讓會(huì)話失效

response.addCookie(new Cookie())

request.getSession 創(chuàng)建

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java中的Cookie是什么_第74节：Java中的Cookie和Session

登錄成功!!!

您還沒(méi)有瀏覽任何商品!

繼續(xù)購(gòu)物

去購(gòu)物車結(jié)算

cat

dog

big

pig

名稱： 數(shù)量:

名稱: 數(shù)量:

名稱： 數(shù)量:

名稱: 數(shù)量:

清空購(gòu)物車

總結(jié)

名稱：數(shù)量:

名稱：數(shù)量: