Value Generator Plugin for Datanucleus HBase

As promised in my last blog post about HBase and Spring Roo I’ll show you now how to create your own Datanucleus plugin in order to support the @GeneratedValue annotation for HBase.

HBase with JPA and Spring Roo

Inspired by Matthias Wessendorf’s blog entry “Apache Hadoop HBase plays nice with JPA” I started playing around with integrating HBase into Spring Roo.

Spring Roo is a lightweight  Java development tool which uses convention-over-configuration principles to provide rapid application development of Java-based enterprise software. It provides all the nice things like auto generating getters, setters, unit tests and persistence methods, scaffolding and so on. Therefore it makes heavy use of AspectJ to put all the auto generated code into separate files (with extension .aj) so you can safely change all Java files without interfering with Roo’s code generation engine. One of the best things in Roo (compared to Grails) is that everything generated is plain Java, so if you at some point in time don’t want to use Roo anymore you can easily merge all the aspects into your Java files and continue without using Roo (even though I wouldn’t recommend that). If you have not worked with Roo up to now check out the quick tutorial in the Roo Reference Documentation.

HBase is an open source, non-relational, distributed database modeled after Google’s BigTable and is written in Java. It is developed as part of Apache Software Foundation’s Hadoop project, providing BigTable-like capabilities for Hadoop. Therefore it’s a good alternative for all folks who do not want to host their application on the Google App Enginge.

The installation of Hadoop and HBase is relatively straight forward and well documented in the HBase wiki. According to the documentation there is also a way to set it up using windows and Cygwin, but I’ve to tried it. I did my test installation in a VMWare with Ubuntu Server 10.04 LTS.

The Datanucleus guys are offering a JPA and JDO integration for HBase and many other databases under the Apache 2 open source license. Event though the HBase plugin from Datanucleus still has some limitations (like no auto generated IDs), you can either work around those restrictions by using JPA in a slightly different way or writing a simple plugin to one of the dozens plugin points offered by Datanucleus. In my next blog I’ll show you how to auto generate IDs using the JPA annotation @GeneratedValue by writing your own simple Datanucleus plugin .