Outbound processes
JCA was introduced (as JCA 1.0) in J2EE 1.3 to provide outbound communications from application servers to enterprise information systems. Defined simply, outbound processes are processes that are sent from your application out to the enterprise information system. So, a client application, running on the WebSphere® Application Server, sends a request with business data to the adapter, the adapter processes the request, and returns the result of the operation to the client application. For example, the client application that needed data from the enterprise information system would send a Java data binding with the query to the adapter component. The client application would receive, in return, the results in the form of a Java data binding. The client application does not need to know how the function worked or how the data was structured. The J2C Bean would perform all the interactions with the actual EIS function.
Inbound processes
JCA 1.0 did not provide a mechanism for inbound communications from EISs to application servers, such as asynchronous message delivery or event notification. Inbound event processing means that the adapter polls the enterprise server at specified intervals for events. When the adapter detects an event, it converts the event data into a business object and sends it to the client application. For example, the client application might want to know about a change to the data on the enterprise server. You can generate a J2C Bean that listens for such events on the enterprise server and notifies client applications with the update. In this case, the interaction begins at the enterprise server.