掌握客户端会话跟踪技术Cookie
掌握服务端会话跟踪技术Sesssion
会话:用户打开浏览器,访问web服务器的资源,会话建立,直到有一方断开连接,会话结束。一次会话中可以包含多次请求和响应。
HTTP协议是无状态协议,每次同一浏览器向服务器请求时,服务器都会将该请求视为新的请求,因此我们需要会话跟踪技术来实现同一会话内数据共享
思考:下图建立几个会话?
每个浏览器都会与服务端建立了一个会话,加起来总共是3个会话。
思考:服务器如何识别多次请求是否来自于同一浏览器?这就需要我们学习今天的内容,会话跟踪技术。
会话跟踪:一种维护浏览器状态的方法,服务器需要识别多次请求是否来自于同一浏览器,以便在同一次会话的多次请求间共享数据
原因:HTTP协议是无状态的,每次浏览器向服务器请求时,服务器都会将该请求视为新的请求,因此我们需要会话跟踪技术来实现会话内数据共享
思考:一个会话中的多次请求为什么要共享数据呢?有了这个数据共享功能后能实现哪些功能呢?
购物车功能: 加入购物车和去购物车结算是两次请求,但是后面这次请求要想展示前一次请求所添加的商品,就需要用到数据共享。
记住我功能:当用户登录成功后,勾选记住我按钮后下次再登录的时候,网站就会自动填充用户名和密码,简化用户的登录操作,多次登录就会有多次请求,他们之间也涉及到共享数据
实现方式:
Cookie:客户端会话跟踪技术,将数据保存到客户端,以后每次请求都携带Cookie数据进行访问
Cookie cookie = new Cookie("key","value");
response.addCookie(cookie);
Cookie[] cookies = request.getCookies();
cookie.getName();
cookie.getValue();
<dependencies>
<dependency>
<groupId>JAVAx.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
Cookie[] cookies = request.getCookies();
package com.zbbmeta.cookie;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
/**
* 发送Cookie
*/
@WebServlet(value = "/a")
public class Aservlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//1.创建cookie对象
Cookie cookie = new Cookie("name","lisi");
//2.发送cookie对象到浏览器
response.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
package com.zbbmeta.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
/**
* 获取Cookie
*/
@WebServlet(value = "/b")
public class Bservlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//3.获取客户端携带的所有Cookie,使用request对象
Cookie[] cookies = request.getCookies();
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
if(cookies!=null){
//4.遍历数组,获取每一个Cookie对象:for
for (Cookie cookie : cookies) {
//5.使用Cookie对象方法获取数据
String name = cookie.getName();
String value = cookie.getValue();
writer.write(name+" = "+value+"<br>");
}
}else {
writer.write("cookie不存在<br>");
}
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
Cookie的实现是基于HTTP协议的。
在浏览器 查看Cookie。
package com.zbbmeta.cookie;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
/**
* 发送Cookie
*/
@WebServlet(value = "/a")
public class Aservlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//1.创建cookie对象
Cookie cookie = new Cookie("name","lisi");
//3. setMaxAge(int seconds):设置Cookie存活时间,但是是秒
cookie.setMaxAge(10);
// cookie.setMaxAge(-1);
//cookie.setMaxAge(0);
//2.发送cookie对象到浏览器
response.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
在发送cookie端进行URL编码。
URLEncoder.encode(name,"UTF-8");
在获取cookie端进行URL解码。
value = URLDecoder.decode(name,"UTF-8");
浏览器显示结果。
package com.zbbmeta.cookie;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.NET.URLDecoder;
import java.net.URLEncoder;
/**
* 发送Cookie
*/
@WebServlet(value = "/a")
public class Aservlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//1.创建cookie对象
String name = " lisi";
name = URLEncoder.encode(name,"UTF-8");
Cookie cookie = new Cookie("name",name);
//3. setMaxAge(int seconds):设置Cookie存活时间,但是是秒
cookie.setMaxAge(10);
// cookie.setMaxAge(-1);
//cookie.setMaxAge(0);
//2.发送cookie对象到浏览器
response.addCookie(cookie);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
package com.zbbmeta.cookie;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
/**
* 获取Cookie
*/
@WebServlet(value = "/b")
public class Bservlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//3.获取客户端携带的所有Cookie,使用request对象
Cookie[] cookies = request.getCookies();
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
if(cookies!=null){
//4.遍历数组,获取每一个Cookie对象:for
for (Cookie cookie : cookies) {
//5.使用Cookie对象方法获取数据
String name = cookie.getName();
String value = cookie.getValue();
value = URLDecoder.decode(value,"UTF-8");
writer.write(name+" = |"+value+"<br>");
}
}else {
writer.write("cookie不存在<br>");
}
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
Session:服务端会话跟踪技术:将数据保存到服务端
HttpSession session = request.getSession();
(2)Session对象功能
void setAttribute(String name, Object o)//存储数据到 session 域中
Object getAttribute(String name) //根据 key,获取值
void removeAttribute(String name) //根据 key,删除该键值对
package com.zbbmeta.session;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;
/**
* 1.存储Session数据到服务器
*/
@WebServlet(value = "/c")
public class CServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//1.获取Session对象
HttpSession session = request.getSession();
//2.存储数据到session
session.setAttribute("name","session_wangwu");
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.write("访问了C资源"+"<br>");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
package com.zbbmeta.session;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
/**
* 2.在Session对象中获取数据
*/
@WebServlet(value = "/d")
public class DServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
//1.获取Session对象
HttpSession session = request.getSession();
//2.存储数据到session
Object name = session.getAttribute("name");
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.write("访问了D资源"+"<br>");
if(name!=null){
writer.write(name.toString()+"<br>");
}else {
writer.write("Session数据不存在"+"<br>");
}
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
思考:如果新开一个浏览器,还是同一个session对象么?
答案:上图显示的获取的Session对象不是一个,每一个浏览器都会获取一个新的Session对象。
package com.zbbmeta.session;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;
/**
* 1.存储Session数据到服务器
*/
@WebServlet(value = "/c")
public class CServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
//1.获取Session对象
HttpSession session = request.getSession();
//3.判断Session是否是新对象
boolean aNew = session.isNew();
//4.获取SessionID
String id = session.getId();
writer.write("session 是新的= "+aNew+" session id : "+id+"<br>");
//2.存储数据到session
session.setAttribute("name","session_wangwu");
writer.write("访问了C资源"+"<br>");
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
package com.zbbmeta.session;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
/**
* 2.在Session对象中获取数据
*/
@WebServlet(value = "/d")
public class DServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//get请求
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
//1.获取Session对象
HttpSession session = request.getSession();
//3.判断Session是否是新对象
boolean aNew = session.isNew();
//4.获取SessionID
String id = session.getId();
writer.write("session 是新的= "+aNew+" session id : "+id+"<br>");
//2.存储数据到session
Object name = session.getAttribute("name");
writer.write("访问了D资源"+"<br>");
if(name!=null){
writer.write(name.toString()+"<br>");
}else {
writer.write("Session数据不存在"+"<br>");
}
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//post请求
doGet(request, response);
}
}
查看钝化数据的前台条件是,我们已经有Session对象存储数据。
//5.获取存活时间
int maxInactiveInterval = session.getMaxInactiveInterval();
思考:为什么停留10s后,session对象的存活时间还是1800s?
存活时间表示的是没有访问资源的情况下,如果访问了,则存活时间重新变为1800s.
可以通过web.xml进行配置,单位为分钟。
<?xml versinotallow="1.0" encoding="UTF-8"?>
<web-App xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<session-config>
<!-- 单位是分钟-->
<session-timeout>2</session-timeout>
</session-config>
</web-app>
注意:最好关闭浏览器再打开。