servlet中三大作用域

package com.lanou;

import javax.servlet.ServletContext;
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(urlPatterns = "/scope")
public class ScopeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /*
        * servlet中三大作用域
        *
        * 保存值的范围
        * 1. ServletContext
        * 整个服务器启动期间任何servlet都能获取它的值*/
        ServletContext servletContext = this.getServletContext();
        servletContext.setAttribute("name","Lisa");

        /*
        * 2.session
        * 用户的浏览器启动期间有效*/
        HttpSession session = req.getSession();
        session.setAttribute("name","Rose");
        
        /*
        * 3.request
        * 只在单次请求过程中生效,请求结束就销毁*/
    }
}