Store image to Blobstore from android client and retrieve blobkey and upload url to store in Datastore. - GAE

Question

In my Android application, I want to upload image to the Blobstore, then retrieve an Upload url and the image\'s Blobkey, so I can store the Blobkey in the DataStore.

Answer 1

I am working with endpoints in Android Studio, thanks to SAVANTE, I can finish my code but I had to make small adjustments.

in Servlet 1: I used Endpoints, with this I can handle very easy the OAuth2 in my method:

@ApiMethod(name = "getBlobURL",  scopes = {Constants.EMAIL_SCOPE},
            clientIds = {Constants.WEB_CLIENT_ID,
                    Constants.ANDROID_CLIENT_ID,
                    com.google.api.server.spi.Constant.API_EXPLORER_CLIENT_ID},
            audiences = {Constants.ANDROID_AUDIENCE})
    public BlobAttributes getBlobURL(User user) throws  UnauthorizedException, 
     ConflictException{

        //If if is not null, then check if it exists. If yes, throw an Exception
        //that it is already present
        if (user == null){
            throw new UnauthorizedException("User is Not Valid");
        }

        BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
        String blobUploadUrl = blobstoreService.createUploadUrl("/blobupload");

        //BlobAttributes is a class 
        BlobAttributes ba= new BlobAttributes();
        ba.setBlobURL(blobUploadUrl);
        return ba;
    }

My Backend in endpoints Android Studio, do not let me use JSONObject for this rason I make my own Json: in Servlet 2:

String myJson = "{'servingUrl': '" + servingUrl +
                        "', 'blobKey': '" + blobKey.getKeyString() + "'}";

            PrintWriter out = resp.getWriter();
            out.print(myJson);
            out.flush();
            out.close();

I hope works for somebody else, I spent 48 hours trying to understand and operate Blobstore.

Edit:

For make a authenticated call from client this is the way using Google credentials:

accountName = settings.getString(start.KEY_ACCOUNT_NAME, null); //Email account that you before save it
            credential = GoogleAccountCredential.usingAudience(getActivity(),
                    start.WEB_CLIENT_ID); //WEB_CLIENT_ID is your WEB ID in Google Console
            credential.setSelectedAccountName(accountName);

When build your Endpoint put your credential:

PostEndpoint.Builder builder = new PostEndpoint.Builder(AndroidHttp.newCompatibleTransport(), new AndroidJsonFactory(), credential)
                        .setRootUrl(getActivity().getString(R.string.backend_url_connection));
                myApiService = builder.build();

For Get the Account Name of the client, use Plus API

accountName = Plus.AccountApi.getAccountName(mGoogleApiClient);

Read the links down in the comments, with Google documentation for good understand this.