December 19, 2006
TechBookReport on 'Beginning Hibernate'
TBR writes "Although it sounds like something to do with electrical resistance in AC circuits, 'impedance mismatch' describes the issues that arise when dealing with the different conceptual bases of object oriented development and relational databases. Developers model their domain with classes and objects, but when it comes to persisting these objects there's usually a relational database as the data store - which means having to stuff those nice object hierarchies into relational tables. For very small applications hand-coding provides an answer - a bit of SQL and some code can work wonders. Anything bigger requires an object-relational mapping (ORM) layer to bundle objects into and out of those relational tables. While there's a certain satisfaction in rolling your own ORM layer, the fact is that there are plenty of powerful open-source ORM frameworks, and in the Java world at least Hibernate is one of the best known and most widely used."