Develop Reference

Azure Mobile Services with Android

I am very new to both Android development & Azure Mobile Services. I have a decent knowledge of Java so Android development is not proving to be too difficult. Although, I am struggling to gain a good knowledge of working with Azure Mobile Services.
I have little knowledge of REST API's but will be able to learn quite quickly if required. My main concerns/questions are as followed:
Can I build my Android app by using Mobile Services Data & API's alone. i.e the simple table values and the basic CRUD API's?
If not, how should I approach building the application?
I want to cater for multiple column queries, table relationships (1 .. n , inheritance) and I also would like to use JSON objects as parameters for a more lightweight communication rather than passing my full Java objects.
Also, is the possibility of setting up an SSL available?
Any help would be appreciated.

thanks for trying out Azure Mobile Services. Here is a good tutorial on how to get started with Android.
To answer your questions specifically:
Generally a CRUD API for data storage and a custom API for arbitrary REST calls should be all you need for a straightforward app, and those are all offered in the box with Mobile Services. The one thing we don't offer today (but are considering) is support for duplex messaging (WebSocket), which you might need if you are building a realtime app or game.
Mobile Services does not support object trees on the client, but you can still have them in your server database. You just have to write some custom code to "flatten" the hierarchy before you send it to the client.
Every mobile service supports HTTPS by default. We do not currently allow you to do a custom SSL cert.

Document management system using Google Cloud Storage

I am currently working on different aspect Google App Engine and still in study phase and build some small apps and deployed it on cloud. Recently when i was installing a command line to for cloud storage(i.e. gsUtil) I encountered versioning support on cloud storage and was able to retrieve old objects or deleted objects through gsUtil . So building a document management system on GAE is good idea with Google cloud storage or I should be using Google drive SDK ?
Please guide me on this problem .
Thanks in advance

Completely different products for completely different use cases.
Google Cloud Storage is a storage on cloud, no more abstractions. If you want to build a document management system from scratch, you can prefer it as the storage provider.
If you build an app on the top of Google Drive, you inherit a file system abstraction, user management, a permissions model and etc. But you don't own the users, neither their drives. Additionally, Drive's quota management is fined tuned for "per-user" usage. Most people think creating a single Drive account and logically share it among their users on the application level will work. It's unlikely to scale due to the quota limitations.

Using 2-legged OAuth with Google Tasks API in Java

I’m trying to build a Sync application for Google Task API using Java.
An additional constraint I have is to use 2-legged OAuth.
I followed the article Using 2-legged OAuth with Google Tasks API for Google Apps domain administrators but the code sample they provided for Java doesn’t compile with the latest API libraries.
Also, there is lot of material available about Google Tasks, but either its deprecated or using non existent API/references.
It would be great help if someone could point me to a relevant article or working example.
Articles and sites I referred to:
https://developers.google.com/google-apps/tasks/
Thanks

Can you explain the constraint to use 2LO? There are ways to write sync apps that use OAuth2 and tokens, which has more current library and sample support. You can request "offline" access and save the refresh token in the client. Then you can continually sync that data for the user in question. Is the reason you need 2LO that you need to do this for an entire domain of users without prompting them?
In any case, the tasks api and 2LO should be compatible even if you're having issues with some libraries. I can't comment on the state of all the samples and libraries, but if you follow the steps to approve the tasks api scope for your client_id in ManageOAuthClients and you know the ids of your domain users, and you sign your requests properly, it should 'just work'

Amazon access credentials in Android App

Amazon Cloud Services (AWS) has provided the ready to use Library to make calls to SDB, S3, SNS etc right from your Android app. This makes it really easy for a mobile developer who is not familiar with web services and web applications to create a completely scalable cloud based app.
We give the Amazon Access Credentials in these API calls to connect to our cloud Account; My question is:
How do I effectively use Key rotation in the app, since I would be distributing the app, once the change in key could mean a period disruption for the existing users.
Would hard coding the Amazon Access Credentials inside the code (as a field Constant etc) make it vulnerable to extraction? Via decompiling etc.?

I talked to the Amazon Advocate for our region and he told that Amazon client library is not designed for such a purpose.
It could be used in for in-house apps (not being published), like client-demo apps.
If you're bundling the Credentials with an app to be published in open market (not recommended), use IAM and create a separate credential with with restricted access.
If you're building an app like Instagram, you may have to setup a web server to proxy your calls to Amazon (effectively making the client library useless).
Obviously, I was not very convinced. I think an entire client library to Amazon communication (bypassing the need for a webserver) could be a great advantage for Mobile devs.

Re:
Would hard coding the Amazon Access Credentials inside the code (as a field Constant etc) make it vulnerable to extraction? Via decompiling etc.?
Yes, by looking for strings and patterns in the binary. Also decompiling, but that'd often not be necessary.
The first question is, what sort of threats are you trying to protect against? Governments? Paid hackers? Or you just want to make it not easy to gain access other than via the app?
Limit the access the keys have to just the data that the app needs.
Store the keys in the app in several pieces. Modify them in some way (eg ROT47), then re-combine when sending to the service.
Don't put all of the key information into the app. Require use of another security device such as the Amazon MFA
Install monitoring to detect unusual patterns of access that could indicate access from outside of the app.

Is there a technology stack that makes connecting android applications easily?

I'm creating an android application. Most of the functionality will be done offline, however I need to build some dependency between users of the application, such as being able to see peoples "high scores" and to communicate between users, and sending each other in-app messages.
Therefore, I'll need a webserver which the app can connect to in order to store such information. I imagine the app will make REST calls to get high scores.
I'm trying to avoid the overhead of having to create a fully functional web application (SpringMVC for example). Is there any application that makes this simpler?
What is a good, simple web stack I could use for this?

We use the Java RESTlet framework for creating RESTful interfaces for our mobile apps, and deploy via Google AppEngine. I shared a series of screencasts on YouTube demonstrating this approach that you might find useful. The RESTlet framework used in the screencasts is a few versions old, but this should help you get up to speed fairly quickly. We like this particular approach because it's straightforward for Android developers (who are already proficient in Java), scales well, and its free until you hit Google's quotas.