ajax.js

自己做的一个火车票售票网站是课程设计 用的是servlet+jsp 数据库是ms

function checkUser(){
	var obj = document.getElementById("newUserName");
	var userName = obj.value;
	send_request("LoginAjaxServlet?name="+userName);
}
var http_request = false;
function send_request(url)
{	http_request = false;

    //开始初始化XMLHttpRequest对象

    if(window.XMLHttpRequest)

    { //Mozilla 浏览器

        http_request = new XMLHttpRequest();

        if (http_request.overrideMimeType) {//设置MiME类别

            http_request.overrideMimeType('text/xml');

        }

    }

    else if (window.ActiveXObject)
    { // IE浏览器
        try
        {
            http_request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e)
        {
            try
            {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e) {}
        }
    }
    if (!http_request)
    { // 异常，创建对象实例失败
        window.alert("不能创建XMLHttpRequest对象实例.");
        return false;
    }
    http_request.onreadystatechange = processRequest;
    
    // 确定发送请求的方式和URL以及是否同步执行下段代码
    http_request.open("GET", url, true);
    http_request.setRequestHeader("Content-Type","text/html;charset=gb2312");   
    http_request.send(null);
}
function processRequest()
{
    if (http_request.readyState == 4)
    { // 判断对象状态

        if (http_request.status == 200)

        { // 信息已经成功返回，开始处理信息

            var returnStr = http_request.responseText;
            document.getElementById("showText").innerHTML = returnStr;
         }
    }
}