How do i determine the stream size from an uploaded file from a website which i want to insert in Google Drive

问题

I'm trying to upload files to Google Drive with ProgressListener and ChunkSize enabled (thus with DirectUploadEnabled disabled). This way i have a more reliable upload and the possibility for a progress indication to the user.

I transfer the files from the GWT website to the GAE with a FormPanel and a FileUploadField which POSTS the file to GAE on submit(). On the GAE i receive the file with an UploadServlet which uses org.apache.commons.fileupload to receive the documents as a stream. I don't want to receive the complete documents on the GAE because the documents are to big. Therefore i start the upload (insert) to Google Drive with the received stream from the incoming request.

Now there's a problem; for the insert i need to know the size of the stream;

int lContentLength = getRequest().getContentLength();
FileItemStream lFileItemStream = getFileItemStream();
InputStream lInputStream = lFileItemStream.openStream();
BufferedInputStream lBufferedInputStream = new BufferedInputStream(lInputStream);
InputStreamContent lInputStreamContent = new InputStreamContent(pContentType, lBufferedInputStream);
lInputStreamContent.setLength(lContentLength);

My first guess was the ContentLengt from the incoming Servlet request. But this is not correct because this concerns the complete request (which also contains other fields which are used as parameters). Without the Drive option DirectUploadEnabled i need the exact stream size from the uploaded document, otherwise the upload stall's at the end...

How do i grap this document size? The Google example is stupid because it uses a local file;

https://code.google.com/p/google-api-java-client/wiki/MediaUpload

Yes from a local file it is easy to get the file size (mediaFile.length()). But from a website ... Several sites specify it is not possible to grab the file size before submit() from the website, and it seems also impossible to determine the stream-size on GAE without loading the complete file...

How do i determine this streamsize? Is there another solution for this problem?

来源：https://stackoverflow.com/questions/15234028/how-do-i-determine-the-stream-size-from-an-uploaded-file-from-a-website-which-i