多部分/表单数据表单提交

Question

In IE9, when I submit a form (enc-type: multipart/form-data) with a file to a java servlet something goes wrong. I have trouble locating the error and finding a solution. The Content-Length is 0 when it's not working. That's the only difference in the request header. And there is no difference in the request message.

How I try to retrieve the form data in java serlvet (using org.apache.commons):

ServletFileUpload upload = new ServletFileUpload();
if (!ServletFileUpload.isMultipartContent(request)
    throw new Exception("Invalid parameters");
FileItemIterator itr = upload.getItemIterator(request);
while(itr.hasNext()
{
    // This never gets run when the error occurs (Content-Length: 0).. 
}

I assume there is something wrong with the form submit? Does anyone have any idea what could be wrong? In chrome it allways works.

UPDATE: essential parts of html form:

<form name='uploadparticipants' action='ParticipantUploader' method='post' encoding='multipart/form-data' enctype='multipart/form-data' target='upload_target' onsubmit='admin.uploadCourseParticipants()'>
// Some input fields inside a table, among them a file input //
<input type='submit' value='somevalue'>
</form>

Answer 1

1. Please make sure you have explicitly added method="post" during form creation.

2. Also, when creating forms dynamically in Internet Explorer (both 6 and 7) using Javascript, you need to also set the encoding attribute, for some reason. So although the attribute is called enctype, setting the enctype does nothing. Please try adding the following code:

   form.setAttribute('encoding', 'multipart/form-data');