Looking for an architectural pattern to solve the following problem.
In my architecture, I have a Stateless EventDispatcher EJB that implements:
public void dispatchEvent(MyEvent ev)
This method is called by a variety of other EJBs in their business methods. The purpose of my EventDispatcher is to hide the complexity of how events are dispatched (be it JMS or other mechanism).
For now let's assume my bean is using JMS. So it simply looks at the event passed it, and builds JMS messages and dispatches them to the right topic. It can produce several JMS messages and they are only sent if the surrounding transaction ends up being committed successfully (XA transaction).
Problem: I may be looking at transactions where I send thousands of individual messages. Some messages might become invalid because of other things that happened in a transaction (object Updated and then later Deleted). So I need a good deal of logic to "scrub" messages based on a context, and make a final decision on if it is one big JMS batch message or multiple small ones.
Solutions: What I would like to is use some sort of "TransactionalContext" object and use it in my Stateless EJB to "Buffer" all the events. Then I need a callback of some sort to tell me the transaction is about to commit. This is something similar to how we use EntityManager, i can make changes to entities, and it holds onto changes and is shared between stateless EJBs. At "flush" time (transaction complete) it does its logic to figure out what SQL to execute. I need a TransactionContext available to my stateless bean that has a unique session per transaction, and, has a callback as the transaction is about to complete.
What would you do?
Note that I am NOT in a valid CDI context, some of these transactions are starting because of @Schedule timers. Other transactions begin because of JMS MDBs.
