欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

Ajax异步XMLHttpRequest对象

程序员文章站 2022-07-12 18:52:53
...

示例Ajax:

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Ajax</title>
</head>
<body>

<div style="text-align: center;">
	<button onclick="loadName()">测试Ajax</button>
</div>

</body>
<script type="text/javascript">
function loadName() {
	var xmlHttp;
	if(window.XMLHttpRequest){
		xmlHttp=new XMLHttpRequest();
	}else{//IE 5,6的支持
		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
	//xmlHttp.open("get", "testAjax", true);
	//xmlHttp.open("post", "testAjax", true);
	
	/*
	//get请求
	xmlHttp.open("get", "testAjax?name=Anner&age=24", true);
	xmlHttp.send();
	*/
	//post请求
	xmlHttp.open("post", "testAjax", true);
	xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
	xmlHttp.send("name=Anner&age=24");
}
</script>
</html>

  XMLHttpRequset对象相应服务器

onreadystatechange事件

当请求被发送到服务器时,我们需要执行一些基于响应的任务

当readystate改变时,就会触发onreadystatechange事件

XMLHttpRequest对象的三个重要的属性:

1、onreadystatechange存储函数或函数名,每当readyState属性改变时,就调用该函数

 

readyState存有XMLHttpRequest的状态,从0到4发生变化

0:请求未初始化

1:服务器连接已经建立

2:请求已接收

3:请求处理中

4:请求已完成,且相应已就绪

status:

200:OK

404:未找到页面

如需获得来自服务器的相应,使用XMLHttpRequest对象的responseText或responseXML属性

responseText获得字符串形式的响应数据

responseXML获得XML形式的响应数据

   Ajax返回后台Servlet数据

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Test Ajax</title>
</head>
<body>

<div style="text-align: center;">
	<button onclick="loadName()">测试Ajax</button>
	<input type="text" name="te" id="te">
</div>

</body>
<script type="text/javascript">
function loadName() {
	var xmlHttp;
	if(window.XMLHttpRequest){
		xmlHttp=new XMLHttpRequest();
	}else{//IE 5,6的支持
		xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
	}
	//xmlHttp.open("get", "testAjax", true);
	//xmlHttp.open("post", "testAjax", true);
	
	/*
	//get请求
	xmlHttp.open("get", "testAjax?name=Anner&age=24", true);
	xmlHttp.send();
	*/
	
	//alert("readyState:"+xmlHttp.readyState+"status状态"+xmlHttp.status);
	xmlHttp.onreadystatechange=function(){
		//alert("readyState:"+xmlHttp.readyState+"status状态"+xmlHttp.status);
		if(xmlHttp.readyState==4 && xmlHttp.status==200){
			//alert(xmlHttp.responseText);
			document.getElementById("te").value=xmlHttp.responseText;
		}
	};
	//post请求
	xmlHttp.open("post", "testAjax", true);
	xmlHttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
	xmlHttp.send("name=Anner&age=24");
	
	
}
</script>
</html>

  

	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		//req.setCharacterEncoding("utf-8");
		//String name=req.getParameter("name");
		//String age=req.getParameter("age");
		//System.out.println(name+" "+age);
		resp.setContentType("text/html;charset=utf-8");
		PrintWriter out =resp.getWriter();
		out.println("ajax返回");
		out.flush();
		out.close();
	}