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I am a C# developer who recently decided to venture into the mobile dev world specifically android dev using java. It has been a smooth ride until now. While I'm usually able to follow the tutorials on the android developers site and other sites easily, uploading an image/video to the app engine blobstore or cloud storage seems to be a bit over my head. I cant seem to wrap my head around the process. I have already done the necessary steps to get my app running on app engine. I am able to register devices and save basic entities to the cloud but I cant seem to get any of the tutorials to work form me. Basically my app allows users to take images or videos and then have them posted to my back end as part of a file sharing type of game. I am not asking for someone to give me code that can accomplish this, instead pointing me to a very thorough tutorial would be great!

1.I need understand the role of a servlet (most examples use this for uploading to blobstore)
2.Where should the servlet reside?
3.Is there another way to do this without using a .jsp page for the file uploading ?
4. I have set up the app engine back end for my project including endpoints. Is there a way to send the images/video that way to the server and still be able to retrieve a serving url to fetch the image/video later?

I have been stuck on this for a week now and I'm getting quite discouraged as I cannot seem to adapt any of the tutorials that I have read to suite my needs. There are a few dark spots in my mind where the entire process is concerned. Since I am not familiar with java, servlets etc I'm stumbling in the dark and I just need a lamp to light my path. I think i'm just a step or two away.

BTW I have looked at these questions and tried the code suggested to no avail before deciding to post my own.

Upload to Appengine Blobstore in Android
BlobStore vs Cloud Storage for storing user uploaded images
Upload image from Android to Google Cloud Storage or Google App Engine Blobstore

Please help!

NOTE: I don't have an interface where the user gets to choose the image/video as it is to be taken directly from the camera and sent to the server(not sure that makes a difference).

Community
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dis.iz.peez
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2 Answers2

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You need to do a lot more reading. First understand servlets in general. Then learn how to use the blobstore or cloud storage api. Then read how to post directly to blobstore (not to the servlet) with a post-save servlet callback.

Zig Mandel
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  • I have done quite a bit of reading and I do have an ok understanding of how it would work I havent been able to find a good adaptable example showing how to post to the blobstore without a servlet. What exactly is a postback servlet callback? – dis.iz.peez Mar 07 '14 at 19:55
  • I have since this post read a lot about servlets and backends in general. I will mark this as the answer since it lead me down the right path. Thanks @zig ! – dis.iz.peez Apr 21 '14 at 21:38
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Welcome to the world of Java!

I'll try my best to explain the Servlets/JSPs part. I dont know a whole lot about Google app engine.

1) Servlets are nothing but Java objects but with more priveleges. Servlets know how to handle a web request! There are many things that come to mind when we talk about web request processing:

  1. who maps the URL to this servlet?
  2. Who gives this servlet user request parameters?
  3. How can I guarantee only authorized users can access this servlet?

list goes on......

Answer to all above questions is a web container. And in the world of Java only one web container rules (others might differ): Apache Tomcat.

In short, servlets are Java objects created for you by Tomcat.

Where should the servlet reside?

They reside in Tomcat.

Is there another way to do this without using a .jsp page for the file uploading ?

You dont need a JSP to send requests to a servlet. You can use jquery, python or anything else. As long as its a valid web request.

I have set up the app engine back end for my project including endpoints. Is there a way to send the images/video that way to the server and still be able to retrieve a serving url to fetch the image/video later?

See the tutorial here. Especially 'Implementing Tweet My Picture' section.

Google app engine has Java API (along with python) and the best way to submit web request to that API using Java is servlets. That's why many example are in servlets. I think.

Here's what i would do if I were you:

  1. Setup tomcat. There are many options. So reply if you are not sure.
  2. Deploy your handler servlet that'll use Google app engine Java API.
  3. Send your image files to blobstore (not the servlet). See the tutorial. App engine will forward blob related information to the handler servlet you created in step 2.
  4. Use Blobstoreservice in that servlet so that users can access that uploaded image.

Let us know if this helped.

Boss Man
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