MediaSource is null for an attachment on google sites

[Paul Gestwicki]

I am writing a program to upload jars to GoogleSites for use in JNLP.
It works fine right now, always pushing the latest build up to
GoogleSites. I am trying to add a feature whereby the jar is only
uploaded if it's newer than the one that's up there. The best
heuristic I could come up with to try is to check if the file sizes
are different---not perfect, but good enough.

My existing, working code:

public static AttachmentEntry updateFile(AttachmentEntry entry, File
newFile)
throws IOException, ServiceException {
entry.setMediaSource(new MediaFileSource(newFile, mediaTypes
.getContentType(newFile)));
return entry.updateMedia(true);
}

I tried doing a check on file size like this:


public static AttachmentEntry updateFile(AttachmentEntry entry, File
newFile)
throws IOException, ServiceException {
long attachmentSize = entry.getMediaSource().getContentLength();
long fileSize = newFile.length();
System.out.println("--- attachment size: " + attachmentSize
+ ", file size: " + fileSize + "\n --> They are "
+ (attachmentSize == fileSize ? "equal" : "unequal"));

entry.setMediaSource(new MediaFileSource(newFile, mediaTypes
.getContentType(newFile)));
return entry.updateMedia(true);
}

However, getMediaSource returns null for all the attachments on the
filecabinet page, including the .jar and .jnlp files that are there.

Am I not using getMediaSource correctly, or is there another way to
accomplish my goal?