通过Ajax上载文件实际上是不可能的。您仍然可以使用隐藏的iframe在后台上传文件，并评估响应（位于iframe内）或在上传完成后触发另一个ajax调用。
<g:form name="upload-form" action="upload" method="post" enctype="multipart/form-data" target="hidden-upload-frame"> File: <input type="file" name="myFile" /> <button type="submit">Upload</button></g:form><iframe id="hidden-upload-frame" name="hidden-upload-frame" onload="onUploadComplete"></iframe><script type="text/javascript"> function onUploadComplete(e) { // Handle upload complete alert("upload complete"); // evaluate iframe content or fire another ajax call to get the details for the previously uploaded file }</script>另一种选择是使用基于Flash的上传机制（例如swfupload）代替iframe。
