The idea is to use MDA approach for conversion of one card schema to the other one. The traditional way is to write java code field by field. What I suggested is to use MDA (Model Driven Approach) for the conversion. The idea is to define the model in a kind of object model, use XML to make the model and create the framework to execute the mode.
During the implementation I understood that usage of standard EL (Expression Language) would be very handy and I successfully tried Juel.
In this way, the conversion rules are much more meaningful and understandable. It is also possible to change them dynamically without recompiling.
There is only one important negative point and that one is type safety. Not all expression in Juel are checked against syntax in type of loading. My next task on this subject is to find how can I guaranty type safety, at least at the same level as java code.