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前端代码：
<html>
<head>
<meta charset="UTF-8">
<title>异步请求</title>
<script type="text/javascript" src="jquery-3.3.1.js"></script>
<script type="text/javascript">
//利用jquery实现ajax使用
$(document).ready(function(){
$("#btn").click(function(){
$.post("${pageContext.request.contextPath}/ajaxServlet?time="+new Date().getTime(),
function(data,status){
alert("数据：" + data + "\n状态：" + status);
$("#text").val(data);
});
});
});
</script>
</head>
<body>
点击进行异步请求：<input type="button" value="异步请求" name="btn" id="btn" />
<input type="text" id="text" value="唐老鸭"/>
<!-- <div id="text"></div> -->
</body>
</html>
后台代码：
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println(request.getParameter("time"));
String url=request.getServletContext().getRealPath("demo.txt");
File file= new File(url);
//创建输入流
FileInputStream in =new FileInputStream(file);
ServletOutputStream out =response.getOutputStream();
int len=0;
byte[] bs= new byte[1024];
while((len=in.read(bs))>0) {
out.write(bs, 0, len);
}
}
目录结构：