Grails从xhr获取文件

how grails get file from xhr? my ajax

var xhr = new XMLHttpRequest()  
xhr.open("POST", "actionGrails", true)
xhr.setRequestHeader("Cache-Control", "no-cache");
xhr.setRequestHeader("X-File-Name", file.fileName);
xhr.setRequestHeader("X-File-Size", file.fileSize);
xhr.setRequestHeader("Content-Type", "multipart/form-data");
xhr.send(file);

when in my controller

def actionGrails() {
def f = request.getFile('file')
println f//get error
}

any solution for this? thanks

Here is a simple solution: use Fine Uploader. It has a demo page.

The Grails plugin which packages the library is here .