74.【JavaWeb -02】（二）

1.什么是session?
(1).服务器会给每一个用户(浏览器)创建一个Session对象;
(2).一个Session单独占一个浏览器
(3).用户登入之后，整个网站都能访问它。==》保存购物车的信息
2.Session和Cookie的区别:
(1).Cookie是把用户的数据写给用户的浏览器，浏览器保存 (可以保存多个)
(2).Session是把用户的数据写到用户独占的Session中，服务器端保存 （保存重要的）
(3).Session由服务端创建，不要我们new,
3.Session使用场景:
(1).保存一个用户登入信息，可以登入多个服务端的网页
(2).在整个网站中会使用的数据，将其保存在session中，

package com.Jsxs.Cookie;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
public class Demo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setCharacterEncoding("UTF-16");
        req.setCharacterEncoding("UTF-16");
        resp.setContentType("text/html");
        PrintWriter out = resp.getWriter();
//      请求得到session
        HttpSession session = req.getSession();
//       给session中存东西
        session.setAttribute("name","吉士先生");
//        获取session的ID
        String id = session.getId();
//        判断session是否是新的
        if(session.isNew()){
            out.write("session新的装备已经创建,ID"+id);
        }else {
            out.write("session已经在服务器中存在了"+id);
        }
//        实质: 调用session的时候，会自动生成一个cookie,所以此时此刻会显示所有
//        Cookie cookie = new Cookie("JSESSIONID","id");
//        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

package com.Jsxs.Cookie;
import javax.servlet.ServletException;
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;
import java.net.URLDecoder;
import java.net.URLEncoder;
public class Demo5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-16");
        resp.setCharacterEncoding("UTF-16");
        resp.setContentType("text/html");
        PrintWriter out = resp.getWriter();
        HttpSession session = req.getSession();
        String name = (String) session.getAttribute("name");
        out.write(name);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

package com.Jsxs.Cookie;
import com.Jsxs.Cookie.Object.Person;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;
public class Demo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setCharacterEncoding("UTF-16");
        req.setCharacterEncoding("UTF-16");
        resp.setContentType("text/html");
        PrintWriter out = resp.getWriter();
//      请求得到session
        HttpSession session = req.getSession();
//       给session中存东西
        session.setAttribute("name",new Person("吉士先生",23));
//        获取session的ID
        String id = session.getId();
//        判断session是否是新的
        if(session.isNew()){
            out.write("session新的装备已经创建,ID"+id);
        }else {
            out.write("session已经在服务器中存在了"+id);
        }
//        实质: 调用session的时候，会自动生成一个cookie,所以此时此刻会显示所有
//        Cookie cookie = new Cookie("JSESSIONID","id");
//        resp.addCookie(cookie);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

package com.Jsxs.Cookie;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class Demo6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession session = req.getSession();
//        移除name
        session.removeAttribute("name");
//        注销session
        session.invalidate();
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

<session-config>
<!--        单位是min-->
        <session-timeout>1</session-timeout>
    </session-config>

Java Server Pages: Java服务端页面，也和Servlet一样，用于动态的web开发
1.最大的特点:
(1).写JSP就像在写HTML
(2).写JSP不用在web里面注册信息。
2.区别:
(1).HTML只给用户提供静态的数据
(2).JSP页面中可以嵌入JAVA代码，为用户提供动态数据

1.服务器内部工作:
Tomcat中，有一个work目录，IDEA使用Tomcat会在IDEA中产生一个work目录

2.我的电脑地址:
C:\Users\22612\AppData\Local\JetBrains\IntelliJIdea2021.1\tomcat\246560f4-bb63-4256-89d3-6446385cc047