title: Grails get file from xhr
body: <p>how grails get file from xhr?
  my ajax</p>
  
  <pre><code>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);
  </code></pre>
  
  <p>when in my controller</p>
  
  <pre><code>def actionGrails() {
  def f = request.getFile('file')
  println f//get error
  }
  </code></pre>
  
  <p>any solution for this? thanks</p>