Ajax与JSON技术

Ajax实现简单的验证：

<html>
<head>
<Metahttp-equiv="Content-Type"content="text/html;charset=UTF-8">
<title>Inserttitlehere</title>
<scripttype="text/javascript">
	functionajaxValid(){
		varxhr=null;
		varusername=document.getElementById("username").value;
		//创建XMLHttpRequst对象，今后主要靠此对象进行与后台交互
		if(window.ActiveXObject){
			//IE5,6创建对象的方式
			xhr=newActiveXObject("Microsoft.XMLHTTP");
		}else{
		xhr=newXMLHttpRequest();
		}
		//打开连接
		xhr.open("get",'/Web030Ajax/AjaxServlet?username='+username);
		//发送请求
		xhr.send(null);
		xhr.onreadystatechange=function(){
			//readyState码，0代表未初始化，1正在加载2已加载3正在交互4完成
			if(xhr.readyState==4){
				//服务器响应码，200成功
				if(xhr.status==200){
				//	console.log('成功');
				varjsondata=JSON.parse(xhr.responseText);
				//alert(jsondata.info);
				document.getElementById("info").innerHTML=jsondata.info;
				}
			}
		};
	}

</script>
</head>
<body>
<formaction="">
<table>
<tr>
	<td>用户名</td>
	<td><inputtype="text"name="username"id="username"onblur="ajaxValid()"/><spanid="info"></span></td>
</tr>
<tr>
	<td>密码</td>
	<td><inputtype="password"name="password"id="password"/></td>
</tr>

</table>

</form>
</body>
</html>

servlet端

protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{
		//TODOAuto-generatedmethodstub
		Stringusername=request.getParameter("username");
		PrintWriterout=response.getWriter();
		if(username.equals("admin")){
			
			out.print("{\"info\":\"exit\"}");
		}else{
			
			out.print("{'info':'ok'}");
		}
	}

省份

<head>
<Metahttp-equiv="Content-Type"content="text/html;charset=UTF-8">
<title>Inserttitlehere</title>

<scripttype="text/javascript">

	functionff(){
		varselected=document.getElementById("selected1");
		selected.onclick=function(){
			varxhr=null;
			xhr=newXMLHttpRequest();
			
			xhr.open("post","/Web030Ajax/Province");
			xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");//注意这句话的顺序
			xhr.send(null);
			xhr.onreadystatechange=function(){
				if(xhr.readyState==4){
					varprostr=xhr.responseText;
					vararry=JSON.parse(prostr);
					document.getElementById("selected").innerHTML='';
					for(vari=0;i<arry.length;i++){
						document.getElementById("selected").innerHTML+='<option>'+arry[i]+'</option>';
					}
				}
			
		};
	
	}
	}

</script>
</head>
<bodyonload="ff()">
<formaction="">
	<selectid="selected">
		
	</select>
	<inputtype="button"value="dianwo"id="selected1">
</form>

</body>
</html>

servlet端

protectedvoiddoPost(HttpServletRequestrequest,IOException{
		//TODOAuto-generatedmethodstub
		response.setCharacterEncoding("UTF-8");
		PrintWriterout=response.getWriter();
		List<String>provinces=newArrayList<String>();
		provinces.add("山东");
		provinces.add("北京");
		provinces.add("上海");
		Stringjsondata=JSONArray.fromObject(provinces).toString();
		out.print(jsondata);
		out.close();
	}

原文链接：https://www.f2er.com/ajax/163103.html

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