用AJAX提交数据

引入包

<script type="text/javascript" src="js/jquery-1.8.3.min.js"></script>

页面代码
光标离开时触发条件
MessageServle
id和parame为提交的参数名

<script type="text/javascript">
	$(function(){
		$("[id=ids]").blur(function(){

			var idss=$(this).val();
			  $.post("MessageServlet",{"id":idss,"parame":"logintemp"},function(xt){
	    	    $("[id=ids]").next().html(xt);

	    	});
		});
	})
</script>

后台代码

private void logintemp(HttpServletRequest request, HttpServletResponse response) {
		String id=request.getParameter("id");
		User user=null;
		user=userdao.findById(Integer.parseInt(id));
		System.out.println("登陆检测:"+user);
		String str="";
		if(user==null){
			str="该用户名不存在";
		}
		response.setContentType("text/html;charset=utf-8");
		try {
			PrintWriter out=response.getWriter();
			out.write(str);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}