Saving blobs with Google Endpoint

问题:

I have an app that allows users to save blobs in the blobstore. I have a schema that does so presently, but I am interested in something simpler and less twisted. For context, imagine my app allows users to upload the picture of an animal with a paragraph describing what the animal is doing.

Present schema

1. User calls my endpoint api to save the paragraph and name of the animal in entity Animal. Note: The Animal entity actually has 4 fields ( name, paragraph, BlobKey, and blobServingUrl as String). But the endpoint api only allows saving of the two mentioned.

2. Within the endpoint method, on app-engine side, after saving name and paragraph I make the following call to generate a blob serving url, which my endpoint method returns to the caller

   @ApiMethod(name = "saveAnimalData", httpMethod = HttpMethod.POST) public String saveAnimalData(AnimalData request) throws Exception { ... BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService(); String url = blobstoreService.createUploadUrl("/upload"); return url; }

3. On the android side, I use a normal http call to send the byte[] of the image to the blobstore. I use apache DefaultHttpClient(). Note: the blobstore, after saving the image, calls my app-engine server with the blob key and serving url

4. I read the response from the blobstore (blobstore called my callback url) using a normal java servlet, i.e. public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException. From the servlet, I put the BlobKey and blobServingUrl into the Animal entity for the associated animal. (I had passed some meta data to the blobstore, which I use as markers to identify the associated animal entity).

Desired Schema

This is where your response comes in. Essential, I would like to eliminate the java servlet and have my entire api restricted to google cloud endpoint. So my question is: how would I use my endpoint to execute steps 3 and 4?

So the idea would be to send the image bytes to the endpoint method saveAnimalData at the same time that I am sending the paragraph and name data. And then within the endpoint method, send the image to the blobstore and then persist the BlobKey and blobServingUrl in my entity Animal.

Your response must be in java. Thanks.

回答1:

I see two questions in one here :

1. Can Google Cloud Endpoints handle multipart files ? -> I don't know about this TBH

2. Is there a simpler process to store blobs than using the BlobStoreService?

It depends on the size of your image. If you limit your users to < 1MB files, you could just store your image as a Blob property of your Animal entity. It would allow you to bypass the BlobStoreService plumbering. See : https://developers.google.com/appengine/docs/java/datastore/entities?hl=FR

This solution still depends on how the Cloud Endpoint would handle the multipart file as a raw byte[]...

We encountered the same issue with GWT + Google App Engine in 2009, and it was before the BlobStoreService was made available.

GWT RPC and Cloud Endpoints interfaces share some similarities, and for us it was not possible. We had to create a plain HTTP Servlet, and use a Streaming Multipart file resolver beacause the one from Apache's HTTP Commons used the file system.

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