How to achieve mp3 stream using java Servlet - google-app-engine

Question

Goal: build a servlet so that when I type http://xxx.com/servpage?a.mp3 in browser, I can instantaneously start the playing of this mp3 file. Previously if I put the file on goDaddy as a static file, I can do that. My software can play it right away.
Using Servlet, I can ignore what is after ?, just want this page to return the mp3 dynamically (because in the future I may return any other files). What I got is a long wait (>20 seconds), and then got the player to play it.
I followed some examples, and noticed "attachment" in the example. However, if I remove it, the mp3 won't got played even. I am usign Google App Engine though, but just use the input/outputstream to return the http request. Anyone can help?
public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException ,IOException {
res.setContentType("audio/mpeg3");
OutputStream os = res.getOutputStream();
res.setHeader("Content-Disposition", "attachment; filename="" + "a.mp3";");
res.setContentLength(1000000);
FileService fileService = FileServiceFactory.getFileService();
boolean lockForRead = false;
String filename = "/gs/" + BUCKETNAME + "/" + FILENAME;
AppEngineFile readableFile = new AppEngineFile(filename);
try{
FileReadChannel readChannel = fileService.openReadChannel(readableFile, lockForRead);
InputStream is = Channels.newInputStream(readChannel);
int BUFF_SIZE = 1024;
byte[] buffer = new byte[BUFF_SIZE];
try {
do {
int byteCount = is.read(buffer);
if (byteCount == -1)
break;
os.write(buffer, 0, byteCount);
os.flush();
} while (true);
} catch (Exception excp) {
} finally {
os.close();
is.close();
}
readChannel.close();
} catch(Exception e){
}
}

Answer 1

Few notes:
You are not doing "streaming". Just a plain file download.
To do blob (file) serving, you do not need to read the blob from BlobStore as you do with AppEngineFile. Just serve it directly with blobstoreService.serve(blobKey). See Serving a Blob for an example.
You can get the BlobKey needed in 2. via fileService.getBlobKey(readableFile).
Update:
Just realized you are using Google Cloud Storage, not BlobStore.
In GS, if ACLs are properly set, files are publicly visible via: http://commondatastorage.googleapis.com/BUCKETNAME/FILENAME
Since you are not doing any authentication, you could publicly share the file on GS and then in your servlet just do a 301 redirect to public URL of the file.