Delegator overcomes one of Java's primary limitations: Inheritance as the only means to support reuse and composition. While inheritance is useful, it is only a subclass of what is possible with delegation. This limitation of Java becomes a problem when integrating different components from different sources. It is not always possible to write adapter classes upfront and re-compile all components. Delegator overcomes this problem by enabling object composition on the fly. Delegator has been presented on a few conferences, most notably OT2004:
"The session Delegation in Java - presented by Erik Groeneveld and Willem van den Ende was interesting and thought-provoking - it's about "true delegation" rather than what most people these days think of as delegation (which should possibly be better called "forwarding")"
Delegator is Open Sourced on SourceForge: Delegator.