通过3个Servlet实现ID，Name，Age

一.Java源码

1.demo1.java

import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@WebServlet("/demo1")
public class demo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext=this.getServletContext();
        servletContext.setAttribute("Name","zhangsan");
        servletContext.setAttribute("ID","27");
        servletContext.setAttribute("Age","18");
    }
}

2.demo2.java

import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.util.Enumeration;

@WebServlet("/demo2")
public class demo3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext=this.getServletContext();
        Object id = servletContext.getAttribute("ID");
        resp.getWriter().println("ID:"+id);
        Object name = servletContext.getAttribute("Name");
        resp.getWriter().println("Name:"+name);
        Object age = servletContext.getAttribute("Age");
        resp.getWriter().println("Age:"+age);

    }
}

3.demo3.java

import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet("/demo4")
public class demo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext=this.getServletContext();
        Object id = servletContext.getAttribute("ID");
        resp.getWriter().println("ID:"+id);
        Object name = servletContext.getAttribute("Name");
        resp.getWriter().println("Name:"+name);
        Object age = servletContext.getAttribute("Age");
        resp.getWriter().println("Age:"+age);
        servletContext.removeAttribute("Name");

    }
}

注：先使用tomcat运行demo1，再运行demo2，最后运行demo3