How use Appengine Blobstore (with Android)?

Question

I would like to updload and get pictures from my android application using the appengine Blobstore. I have some issue. I think that I didn't understand very well the process of the blobstore.

Here it's what I have done:

In my client side (Android) I just call an URL (api/pictures/upload/) and post my picture as an array of bytes (byte[]). I think that my client side is good.

In my server side (using appengine in java with Jersey) here is my webservice :

- Upload Web Service : (this function is called directly by android)

@POST
@Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadImageBis(@Context HttpServletRequest req, @Context HttpServletResponse res) throws IOException{

    BlobstoreService bs = BlobstoreServiceFactory.getBlobstoreService();
    bs.createUploadUrl("/upload");
    Map<String, List<BlobKey>> blobFields = bs.getUploads(req);
    List<BlobKey> blobKeys = blobFields.entrySet().iterator().next().getValue();
    if (blobKeys != null && !blobKeys.isEmpty()) {
        BlobKey blobKey = blobKeys.get(0);
        System.out.println("MY KEY: "+blobKey.getKeyString());
    }

    return null;
}

The line " BlobstoreService bs = BlobstoreServiceFactory.getBlobstoreService(); " create an error : Must be called from a blob upload callback request
But after a while it is persist (in the datastore or blobstore) and when I check my datastore there is a new tab created called : BlobUploadSession

Then when I tried to get the picture using the key from the console of google I have this mistake : Could not find blob: BlobKey:... I guess that maybe the picture is store in the dataStore instead of the blobstore??

But I think that I did something wrong in my Upload Web Service. If someone can help me and explain what is wrong it's will be great. Thx.

Peter Knego Peter Knego · Accepted Answer · 2014-03-14T15:53:58

Blobupload on GAE is a two step process:

a. Client requests a one-time upload url:

@GET
@Produces("text/plain")
public String uploadImageBis(@Context HttpServletRequest req, @Context HttpServletResponse res) throws IOException{
  BlobstoreService bs = BlobstoreServiceFactory.getBlobstoreService();
  return bs.createUploadUrl("/upload");
}

b. Client POSTs multipart data to that Url:

@POST
@Consumes(MediaType.MULTIPART_FORM_DATA)
public Response uploadImageBis(@Context HttpServletRequest req, @Context HttpServletResponse res) throws IOException{

  Map<String, List<BlobKey>> blobFields = bs.getUploads(req);
  List<BlobKey> blobKeys = blobFields.entrySet().iterator().next().getValue();
  if (blobKeys != null && !blobKeys.isEmpty()) {
    BlobKey blobKey = blobKeys.get(0);
    System.out.println("MY KEY: "+blobKey.getKeyString());
  }

  return null;
}

How use Appengine Blobstore (with Android)?

1 Answers