Active Record v/s Hibernate - Round I

You will have heard of shiny new web application framework called Ruby-on-Rails also known as RoR or simply Rails. It provides complete stack from ORM framework to Web Service. From this post onwards for next couple of posts I will compare and contrast between different components of JEE and Rails. I will begin with Hibernate from JEE and Active Record from Rails. The Round I of the Active Record v/s Hibernate will be on the basis of Mapping

The very first aspect is mapping. Hibernate requires the POJO (Java objects that represents the tables) be mapped with the tables using XML. That means if there is even a slight change in the Database schema such as the length of a particular field is changed, then you will have to make changes not only to the corresponding POJO but also to the mapping file. If you fail to do so, then run-time exception is the most common and the least problem that you will face.

Now lets look at Active Record. The driving principle of Rails is "Convention-over-Configuration" (but version 2.0 is deviating from it, more on that later). So , to map a class to a database table you just have to follow conventions. The conventions are

1. The class derives from ActiveRecord::Base i.e. Base class of ActiveRecord module
2. The name of the class must be same as that of the table
3. The name of the class should start with a capital letter (though this applies to all Ruby classes)

Thats it. No XML, no configuration. Even if there is a change in the table, the corresponding class will adapt to it automatically at runtime through reflection and meta-programming. So that is the difference between Active Records and Hibernate on the basis of Mapping. In the next post I will continue comparing the two on how ORM classes are defined.

Authors Note: I am really sorry for the gap between the posts. It wont happen again (this time for sure). For now on you can expect atleast one post in a week.