笔记-JavaWeb学习之旅12-白红宇

笔记-JavaWeb学习之旅12

阅读量：4583 次

发布时间：2019-06-09

本文共 4475 字，大约阅读时间需要 14 分钟。

会话技术

Cookie:客户端会话技术，将数据保存到客户端

package com.data.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 {        this.doGet(request,response);    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //创建Cookie对象        Cookie cookie = new Cookie("msg","hello");        //发送Cookie        response.addCookie(cookie);        //当访问CookieDemo1的Servlet的时候，会创建一个Cookie对象        //然后把绑定的数据发送给浏览器    }}

package com.data.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 {        this.doGet(request,response);    }    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        //获取Cookie        Cookie[] cs = request.getCookies();        if( cs != null){            //遍历cs，拿到每一个cookie对象            for(Cookie c : cs){                String name = c.getName();                String value = c.getValue();                System.out.println(name+":"+value);            }        }    }}

输出结果msg:helloIdea-a0bb733:23efa255-9ce7-42d9-8d0b-9853348226b8

会话技术原理分析

JSP

概念：Java Server Pages : java服务器端页面，可以理解为一个特殊的页面，其中既可以定义Html标签，又可以定义java代码

JSP的脚本：JSP定义代码的方式

1.<% 代码 %>: 定义的代码，在service方法中。

2.<%! 代码 %>：定义的java代码，在jsp转换后的java类的成员文字

3.<%+ 代码 %>:定义的java代码，会输出到页面上

会话技术_Session

概念：在服务器端会话技术，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

package com.data.session;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.*;import java.io.IOException;@WebServlet("/sessionDemo1")public class SessionDemo1 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        //获取HttpSession对象        HttpSession session = req.getSession();        //当客户端关闭后，服务器不关闭，两次获取的session不是同一个对象        //如果需要相同，可以创建Cookie对象，设置id值，因为session的实现依赖于cookie，只要id值不变就是同一个对象        Cookie cookie = new Cookie("JSESSIONID",session.getId());//JSESSIONID=226E48B3AD9F203B2BCBFCA2E6EA5D71        cookie.setMaxAge(60*60);//一个小时内关闭客户端都是同一个对象，因为他们的ID值相同        resp.addCookie(cookie);        //在服务器端存储数据        session.setAttribute("msg","hello,Session");    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        this.doGet(req,resp);    }}

package com.data.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("/sessionDemo2")public class SessionDemo2 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {       //创建对象        HttpSession session = req.getSession();        //通过键获取值        Object msg = session.getAttribute("msg");        System.out.println(msg);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        this.doGet(req,resp);    }}

session原理：Session的实现依赖于Cookie的，服务在一次会话范围内，多次获取的Session对象是同一个。