文章目录
代码链接:代码
一、会话技术
- 会话:一次会话中包含多次请求和响应。
- 一次会话:浏览器第一次给服务器资源发送请求,会话建立,直到有一方断开为止
- 功能:在一次会话的范围内的多次请求间,共享数据
- 方式:
- 客户端会话技术:Cookie
- 服务器端会话技术:Session
二、Cookie
1.概念
客户端会话技术,是服务器端保存在客户端的一组资源。是要Cookie还没失效,当客户端访问服务器时,保存客户端的Cookie就可以被获取到。
2.Cookie的特点和作用
- 特点:
- cookie存储数据在客户端浏览器
- 浏览器对于单个cookie 的大小有限制(4kb) 以及 对同一个域名下的总cookie数量也有限制(20个)
- 作用:
- cookie一般用于存出少量的不太敏感的数据
- 在不登录的情况下,完成服务器对客户端的身份识别
3.快速入门使用
-
创建Cookie对象,绑定数据
new Cookie(String name, String value)
-
发送Cookie对象
response.addCookie(Cookie cookie)
-
获取Cookie,拿到数据
Cookie[] request.getCookies()
3.1 入门样例
设置一个cookie,然后在界面取出设置好的cookie
CookieDem1.java
package com.jxj4869.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;
@WebServlet("/cookieDemo1")
public class CookieDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Cookie cookie=new Cookie("msg","hello");
response.addCookie(cookie);
request.getRequestDispatcher("/cookie.jsp").forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
cookie.jsp
<%--
Created by IntelliJ IDEA.
User: jiangxiaoju
Date: 2020/3/12
Time: 17:58
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
<title>Cookie</title>
</head>
<body>
cookie
<br/>
msg:${cookie.msg.value}
</body>
</html>
3.2 获取Cookie
package com.jxj4869.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;
@WebServlet("/cookieDemo2")
public class CookieDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1. 获取Cookie
Cookie[] cs = request.getCookies();
//2. 获取数据,遍历Cookies
if(cs != null){
for (Cookie c : cs) {
String name = c.getName();
String value = c.getValue();
System.out.println(name+":"+value);
}
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
3.3 设置Cookie的存活时间
- cookie在浏览器中保存多长时间?
- 默认情况下,当浏览器关闭后,Cookie数据被销毁
- 持久化存储:
setMaxAge(int seconds)
- 正数:将Cookie数据写到硬盘的文件中。持久化存储。并指定cookie存活时间,时间到后,cookie文件自动失效
- 负数:默认值
- 零:删除cookie信息
package com.jxj4869.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;
@WebServlet("/cookieDemo3")
public class CookieDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.创建Cookie对象
Cookie c1 = new Cookie("msg","setMaxAge");
//2.设置cookie的存活时间
//c1.setMaxAge(30);//将cookie持久化到硬盘,30秒后会自动删除cookie文件
//c1.setMaxAge(-1);
//c1.setMaxAge(300);
c1.setMaxAge(0);//删除Cookie
//3.发送Cookie
response.addCookie(c1);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
3.4 Cookie共享问题
- 假设在一个tomcat服务器中,部署了多个web项目,那么在这些web项目中cookie能不能共享?
- 默认情况下cookie不能共享
setPath(String path)
:设置cookie的获取范围。默认情况下,设置当前的虚拟目录,如果要共享,则可以将path设置为"/"
- 不同的tomcat服务器间cookie共享问题?
setDomain(String path)
:如果设置一级域名相同,那么多个服务器之间cookie可以共享setDomain(".baidu.com")
:那么tieba.baidu.com和news.baidu.com中cookie可以共享
package com.jxj4869.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;
@WebServlet("/cookieDemo4")
public class CookieDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.创建Cookie对象
Cookie c1 = new Cookie("msg","你好");
//设置path,让当前服务器下部署的所有项目共享Cookie信息
c1.setPath("/");
//3.发送Cookie
response.addCookie(c1);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
3.5 设置多个Cookie和中文问题
- 可以创建多个Cookie对象,使用response调用多次addCookie方法发送cookie即可。
- 在tomcat 8 之前 cookie中不能直接存储中文数据。需要将中文数据转码—一般采用URL编码(%E3)
- 在tomcat 8 之后,cookie支持中文数据。特殊字符还是不支持,建议使用URL编码存储,URL解码解析
package com.jxj4869.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;
@WebServlet("/cookieDemo5")
public class CookieDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.创建Cookie对象
Cookie c1 = new Cookie("msg1","你好1");
Cookie c2 = new Cookie("msg2","你好2");
Cookie c3 = new Cookie("msg3","你好3");
response.addCookie(c1);
response.addCookie(c2);
response.addCookie(c3);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
先访问cookieDemo5
再访问`cookieDemo2获取cookie。
三、Session
1.概念
服务器端会话技术,在一次会话的多次请求间共享数据,将数据保存在服务器端的对象中。HttpSession
2.Session的特点
- session用于存储一次会话的多次请求的数据,存在服务器端
- session可以存储任意类型,任意大小的数据
- Session和Cookie的区别:
- session存储数据在服务器端,Cookie在客户端
- session没有数据大小限制,Cookie有
- session数据安全,Cookie相对于不安全
3. 快速入门
-
获取HttpSession对象:
HttpSession session = request.getSession();
-
使用HttpSession对象:
Object getAttribute(String name) void setAttribute(String name, Object value) void removeAttribute(String name)
3.1 入门样例
package com.jxj4869.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;
@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//使用session共享数据
//1.获取session
HttpSession session = request.getSession();
//2.存储数据
session.setAttribute("msg","hello session");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
session.jsp
<%--
Created by IntelliJ IDEA.
User: jiangxiaoju
Date: 2020/3/12
Time: 19:57
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Session</title>
</head>
<body>
<h1>Session</h1>
msg:${sessionScope.msg}
</body>
</html>
先访问sessionDemo
,再访问session.jsp
3.2 当客户端关闭后,服务器不关闭,两次获取session是否为同一个?
默认情况下不是。如果需要的话,可以创建Cookie,键为JSESSIONID
,设置最大存活时间,让cookie持久化保存。
package com.jxj4869.session;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
@WebServlet("/sessionDemo2")
public class SessionDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取session
HttpSession session = request.getSession();
System.out.println(session);
//期望客户端关闭后,session也能相同
Cookie c = new Cookie("JSESSIONID",session.getId());
c.setMaxAge(60*60);
response.addCookie(c);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
先访问sessionDemo2
,关闭客户端后再sessionDemo3
两次获取到同一个session。
3.3 客户端不关闭,服务器关闭后,两次获取的session是同一个吗?
不是同一个,但是要确保数据不丢失。tomcat自动完成以下工作
- session的钝化: 在服务器正常关闭之前,将session对象系列化到硬盘上
- session的活化:在服务器启动后,将session文件转化为内存中的session对象即可。
3.4 Session的生命周期
session什么时候被销毁?
-
服务器关闭
-
session对象调用invalidate() 。
-
session默认失效时间 30分钟
选择性配置修改
<session-config> <session-timeout>30</session-timeout> </session-config>