how to add metadata to file when uploading to google-cloud-storage via appengine

Question

I'm uploading a file to GCS via app-engine following the docs

(the code was taken from here )

public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  GcsFileOptions instance = GcsFileOptions.getDefaultInstance();
  GcsFilename fileName = getFileName(req);
  GcsOutputChannel outputChannel;
  outputChannel = gcsService.createOrReplace(fileName, instance);
  copy(req.getInputStream(), Channels.newOutputStream(outputChannel));
}

and here is the copy method:

private void copy(InputStream input, OutputStream output) throws IOException {
    try {
        byte[] buffer = new byte[BUFFER_SIZE];
        int bytesRead = input.read(buffer);
        while (bytesRead != -1) {
            output.write(buffer, 0, bytesRead);
            bytesRead = input.read(buffer);
        }
    } finally {
        input.close();
        output.close();
    }
}

now I want to add this metadata to the file

metadata = "{timestamp:\"01/12/2016\", blabla: 111}"

How do I add this metadata using the code above?

Answer 1

use new Builder().addUserMetadata() insted of GcsFileOptions.getDefaultInstance() ;

public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  GcsFileOptions instance = new Builder().addUserMetadata("timestamp", "01/12/2016").build();
  GcsFilename fileName = getFileName(req);
  GcsOutputChannel outputChannel;
  outputChannel = gcsService.createOrReplace(fileName, instance);
  copy(req.getInputStream(), Channels.newOutputStream(outputChannel));
}