Download blobs from azure mobile service to android

Question

I am using Azure mobile service to upload images from android device. I have followed the documentation to upload images successfully. But I can't find any documentation to download the blobs. Code i used to upload blob is here..

 public void uploadPhoto() {

    if (MainActivity.mClient == null) {
        return;
    }

    final Assignment_Attachment item = new Assignment_Attachment();
    item.setAttachementIdentifier(attachmentUniqueIdentifier);
    item.setFilename(MAP_FILE_NAME_KEY);
    item.setContainerName("schoolonlineblobattachment");

    // Use a unigue GUID to avoid collisions.
    UUID uuid = UUID.randomUUID();
    String uuidInString = uuid.toString();
    item.setResourceName(uuidInString);

    // Send the item to be inserted. When blob properties are set this
    // generates a SAS in the response.
    AsyncTask<Void, Void, Void> task = new AsyncTask<Void, Void, Void>() {
        @Override
        protected Void doInBackground(Void... params) {
            try {
                final Assignment_Attachment entity = addItemInTable(item);
                Log.d("sasquerystring", "sasquerystring" + entity.getSasQueryString());

                // If we have a returned SAS, then upload the blob.
                if (entity.getSasQueryString() != null) {

                    // Get the URI generated that contains the SAS
                    // and extract the storage credentials.
                    StorageCredentials cred = new StorageCredentialsSharedAccessSignature(entity.getSasQueryString());
                    URI imageUri = new URI(entity.getImageUri());

                    // Upload the new image as a BLOB from a stream.
                    CloudBlockBlob blobFromSASCredential = new CloudBlockBlob(imageUri, cred);
                    blobFromSASCredential.uploadFromFile(DATA_FOR_UPLOAD);

                }

                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {

                    }
                });
            } catch (final Exception e) {
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);

            //other logic here

        }

    };

    runAsyncTask(task);
}

I can see a "downloadToFile()" method, but still searching a way to use the SAS thing for download process. Has anybody done this? Any help is appreciated.

Answer 1

To use the SAS, you need a sharedAccessPolicy:

var sharedAccessPolicy = {
   AccessPolicy: {
     Permissions: 'w',
     Expiry: azure.date.​minutesFromNow(5)
   }
 }

The sharedAccessPolicy​.AccessPolicy.​Permissions w' is for uploading while 'r' is for downloading.

Not verified myself yet, but you can try http://inessential.com/2014/04/22/mobile_services_and_blob_storage . See also the code at https://code.msdn.microsoft.com/windowsapps/Upload-File-to-Windows-c9169190 .

Hope it will help.