XMLHttpRequest是怎么用的,为什么我照书上超的实现不了

问题相关代码，请勿粘贴截图

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上面的书上的内容.下面是我写的代码

第一个jsp页面:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title heretitle>
    <style>
        #div {
            width: 200px;
            height: 200px;
            position: absolute;
        }
    style>
head>
<body>
    <form action="">
        <input id="name" name="name"><br/>
        <input type="password" id="pwd" name="pwd"><br/>
        <input type="submit" onclick="check()" value="按钮">
        <div id="div">div>
    form>
body>
    <script>
        var http_request = new XMLHttpRequest();

        function createRequest(url) {
            var http_request = false;
            if (window.XMLHttpRequest) {
                http_request = new XMLHttpRequest();
            }else if (window.ActiveXObject){
                try {
                    http_request = new ActiveXObject("Msxml2.XMLHTTP");
                }catch (e) {
                    try {
                        http_request = new ActiveXObject("Microsoft.XMLHTTP");
                    }catch (e) {
                    }
                }
                if (http_request) {
                    alert("不能创建对象");
                    return false;
                }
            }
            http_request.onreadystatechange = get_result;       //调用返回结果处理函数
            body.innerText = "调用返回结果处理函数\n";
            http_request.open("GET", url, true);        //创建与服务器的连接
            body.innerText = "创建与服务器的连接\n";
            http_request.send(null);            //向服务器发送请求
            body.innerText = "向服务器发送请求\n";
        }


        function get_result() {
            if (http_request.status === 4) {    //判断请求状态
                if (http_request.status === 200) {      //请求成功,开始处理返回结果
                    document.getElementById("div").innerHTML = http_request.responseText;  //设置提示内容
                    document.getElementById("div").style.display = "block"     //显示提示框
                }else {
                    alert("访问错误");
                }
            }
        }
        
        function check() {
            var username = document.getElementById("name").value;
            if (username === "") {
                alert("请输入用户名");
                username.focus();
                return;
            }else {
                createRequest("test.jsp?user=" + username);
                body.innerText = "创建请求\n";
            }
        }
        
    script>
html>

第二个jsp页面:

<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title heretitle>
head>
<body>
    <% 
        List list = new ArrayList<>();
        list.add("zhangsan");
        list.add("lisi");
        list.add("wangwu");
        String user = request.getParameter("name") + "";
        int result = list.indexOf(user);
        if (result != -1) {
            out.print("该用户已被注册");
        }else {
            out.print("注册成功");
        }
    %>
body>
html>
运行结果及报错内容

运行结果没反应