ajax请求下载文件无反应

ajax 只能处理字符串请求，无法处理二进制文件！！！

 var form=$("<form>");
						form.attr("style","display:none");
						form.attr("target","");
						form.attr("method","post");
						form.attr("action","#springUrl('/cloudSign/downAll.htm')");
						var input1=$("<input>");
						input1.attr("type","hidden");
						input1.attr("name","cloudSignContractVo");
						input1.attr("value", JSON.stringify(urls));
						$("body").append(form);
						form.append(input1);
						form.submit();