See our book's chapter on the LEGACY CONNECTIVITY.
There are some real life examples.
Also legacy connectivity in my experience is truly case by case. Every engagement I have had in the last 7 years has involved
JAVA,
J2EE and some legacy system. Each client had some hoem grown technique(s). If it is an IBM legacy system then there is usually something the or a vendor has to solve the problem. Soon vendors will provide JCA / resource adapters for their products. Long story short the infor is all over the place.
THANKS,
Joe Bambara