Simple HBase ORM

When dealing with data stored in HBase, you are quick to come to a conclusion, that it is extremaly inconvenient to reach to it via HBase native API. It is very verbose and you always need to convert between bytes and simple types – a pain. While I wa…When dealing with data stored in HBase, you are quick to come to a conclusion, that it is extremaly inconvenient to reach to it via HBase native API. It is very verbose and you always need to convert between bytes and simple types – a pain. While I wa…

When dealing with data stored in HBase, you are quick to come to a
conclusion, that it is extremaly inconvenient to reach to it
via HBase native API. It is very verbose and you always need to convert
between bytes and simple types – a pain.

While I was working on a project of mine, I thought, why not to easy
those pains and fetch real objects from HBase.

And that’s how this simplistic, hackish ORM came to life. It is no match
for projects like Kundera
(a JPA compliant solution), or n-orm. Nevertheless, it just suits my needs :)

Project sources are hosted on GitHub: https://github.com/zygm0nt/hbase-annotations

To make use of this, you need to have an entity class with annotations:

  • @Column – with argument specifying column family and column name, ie.
    @Column(“cf:column-name”)
  • @Id – will store row key in this property,
  • and optionaly @Value – for Spring Expression Language, in case you
    need to perform some extraction on the value.

Annotations should be on setter methods.

Now you have your model annotated and ready to be fetched from HBase.

The actual work is done with a service class, that should extend class
BaseHadoopInteraction just as class
SimpleHBaseClient does.

Then it is possible to just call:

Note that there are more methods you can use on BaseHadoopInteraction.
You can also do:

  • scan
  • scan with key ranges
  • delete

What you won’t get from this simple ORM is:

  • automatic object updating,
  • nested objects,
  • saving to HBase – ’cause I didn’t have a need for that,

Hope you’ll find this piece of code useful. If you see room for
improvements while staying in project’s scope – please drop me a
message.

And if you are searching for a full-fledged ORM solution for interacting with HBase, just head
straight to Kundera project website :)

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Phonegap / Cordova and cross domain ssl request problem on android.

In one app I have participated, there was a use case:
  • User fill up a form.
  • User submit the form.
  • System send data via https to server and show a response.
During development there wasn’t any problem, but when we were going to release production version then some unsuspected situation occurred. I prepare the production version accordingly with standard flow for Android environment:
  • ant release
  • align
  • signing
During conduct tests on that version, every time I try to submit the form, a connection error appear. In that situation, at the first you should check whitelist in cordova settings. Every URL you want to connect to, must be explicit type in:
res/xml/cordova.xml
If whitelist looks fine, the error is most likely caused by inner implementation of Android System. The Android WebView does not allow by default self-signed SSL certs. When app is debug-signed the SSL error is ignored, but if app is release-signed connection to untrusted services is blocked.



Workaround


You have to remember that secure connection to service with self-signed certificate is risky and unrecommended. But if you know what you are doing there is some workaround of the security problem. Behavior of method
CordovaWebViewClient.onReceivedSslError
must be changed.


Thus add new class extended CordovaWebViewClient and override ‘onReceivedSslError’. I strongly suggest to implement custom onReceiveSslError as secure as possible. I know that the problem occours when app try connect to example.domain.com and in spite of self signed certificate the domain is trusted, so only for that case the SslError is ignored.

public class MyWebViewClient extends CordovaWebViewClient {

   private static final String TAG = MyWebViewClient.class.getName();
   private static final String AVAILABLE_SLL_CN
= "example.domain.com";

   public MyWebViewClient(DroidGap ctx) {
       super(ctx);
   }

   @Override
   public void onReceivedSslError(WebView view,
SslErrorHandler handler,
android.net.http.SslError error) {

String errorSourceCName = error.getCertificate().
getIssuedTo().getCName();

       if( AVAILABLE_SLL_CN.equals(errorSourceCName) ) {
           Log.i(TAG, "Detect ssl connection error: " +
error.toString() +
„ so the error is ignored”);

           handler.proceed();
           return;
       }

       super.onReceivedSslError(view, handler, error);
   }
}
Next step is forcing yours app to  use custom implementation of WebViewClient.

public class Start extends DroidGap
{
   private static final String TAG = Start.class.getName();

   @Override
   public void onCreate(Bundle savedInstanceState)
   {
       super.onCreate(savedInstanceState);
       super.setIntegerProperty("splashscreen", R.drawable.splash);
       super.init();

       MyWebViewClient myWebViewClient = new MyWebViewClient(this);
       myWebViewClient.setWebView(this.appView);

       this.appView.setWebViewClient(myWebViewClient);
       
// yours code

   }
}
That is all ypu have to do if minSdk of yours app is greater or equals 8. In older version of Android there is no class
android.net.http.SslError
So in class MyCordovaWebViewClient class there are errors because compliator doesn’t see SslError class. Fortunately Android is(was) open source, so it is easy to find source of the class. There is no inpediments to ‘upgrade’ app and just add the file to project. I suggest to keep original packages. Thus after all operations the source tree looks like:

Class SslError placed in source tree. 
 Now the app created in release mode can connect via https to services with self-signed SSl certificates.

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