TransXTrail is the simplest database transaction controller API for Java.
JTA, Springs and Tyrex has too many issues/problems. This API is intended to be used in small applications. It also helps you to build a distributed transaction system.
OpenRMI defines a messaging interface. This interface is applied in a one to many fashion, using a controller with many nodes. The nodes connect via RMI to the controller and are assigned work via the same interface.