package com.songzihao.controller;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 *
 */
public class OneServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.通过请求对象向Tomcat索要当前网站中全局作用域对象
        ServletContext application=request.getServletContext();
        //2.将数据添加到全局作用域对象中作为共享数据
        application.setAttribute("key1",100);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

package com.songzihao.controller;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 *
 */
public class TwoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.通过请求对象向Tomcat索要当前网站中全局作用域对象
        ServletContext application=request.getServletContext();
        //2.从全局作用域对象读取数据
        Integer data= (Integer) application.getAttribute("key1");
        System.out.println("TwoServlet得到的共享数据：" + data);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

<?xml version="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">
    <servlet>
        <servlet-name>OneServlet</servlet-name>
        <servlet-class>com.songzihao.controller.OneServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>OneServlet</servlet-name>
        <url-pattern>/one</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>TwoServlet</servlet-name>
        <servlet-class>com.songzihao.controller.TwoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>TwoServlet</servlet-name>
        <url-pattern>/two</url-pattern>
    </servlet-mapping>
</web-app>