What is the best way to connect your J2ee Application to an EIS system that has a CORBA interface by means of asynchronous methods (with call-backs). 1) Just use CORBA from your EJBs, and fork thread out to wait for the callback from the external system and cross your fingers 2) Use an API provided by the system that actually has blocking synchronous calls, but is creating threads itself (same as above from the container�s point of view) 3) Use Common Client Interface JCA 4) Use JMS And especially WHY? Is JCA hard to learn? Any experience with JCA? Any thoughts? Thanks.