Can't upload file to Google Drive from service account - google-apps

Question

I am trying to upload a file to google drive using google service account.
Driver Service
public static Drive getDriveService(String secretKeyFile) throws GeneralSecurityException,
IOException, URISyntaxException {
HttpTransport httpTransport = new NetHttpTransport();
JacksonFactory jsonFactory = new JacksonFactory();
GoogleCredential credential = new GoogleCredential.Builder()
.setTransport(httpTransport)
.setJsonFactory(jsonFactory)
.setServiceAccountId(SERVICE_ACCOUNT_EMAIL)
.setServiceAccountScopes(DriveScopes.DRIVE)
.setServiceAccountPrivateKeyFromP12File(
new java.io.File(secretKeyFile))
.build();
Drive service = new Drive.Builder(httpTransport, jsonFactory, null)
.setHttpRequestInitializer(credential).setApplicationName("appl name").build();
return service;
}
Insert File
private static File insertFile(Drive service, String title, String description,String mimeType, String filename) {
File body = new File();
body.setTitle(title);
body.setDescription(description);
body.setMimeType(mimeType);
java.io.File fileContent = new java.io.File(filename);
FileContent mediaContent = new FileContent(mimeType, fileContent);
try {
File file = service.files().insert(body, mediaContent).execute();
return file;
} catch (IOException e) {
System.out.println("An error occured: " + e);
return null;
}
}
Main Method
Drive service=null;
try {
String secretFile= "somedigit-privatekey.p12";
service = getDriveService(secretFile);
} catch (URISyntaxException ex) {
ex.printStackTrace();
}
File insertFile = insertFile(service, "test title", "File description", "text/plain", "c:\\test.txt");
List list = service.files().list();
System.out.println("Files Id : "+insertFile.getId());
System.out.println("Count Files : "+list.size());
Now, my questions is :
How and where can i check that file was uploaded?
Why it returns the file ID but list.size() is zero.
It returns the download link also but when i paste that link in
browser it doesn't download any file.

Answer 1

You are creating a listing request but not executing it. Use execute method to make the request:
service.files().list().execute();
If you paste the download link into the browser, it will respond with 401, because your download request should also contain a valid Authorization header. Use the following snippet to download the file programmatically.
HttpResponse resp = service.getRequestFactory().buildGetRequest(new GenericUrl(file.getDownloadUrl())).execute();
InputStream stream = resp.getContent();
stream is an input stream for the file content.
Or add an Authorization: Bearer <access token> to the request you're making elsewhere.