Spring Modulith events: publish a domain fact after a valid state change

Name a committed fact

Inventory can publish ReceiptReserved after recording a successful reservation. Dispatch listens for that fact instead of reading inventory.internal. A failed version check must emit no successful event. Transaction event timing determines when a listener sees committed state; the outbox records an external delivery intent with the state change.

Account for listener failure

A synchronous listener can fail the publisher; an asynchronous one can fail after the caller returns. Spring Modulith's publication registry can persist outstanding transactional-listener publications when installed and configured. That is not identical to Kafka acceptance. The isolated module slice now checks in-process publication for an accepted reservation and silence for a rejected one. Registry persistence and restart remain untested.

Boundary sketch

record ReceiptReserved(String tenantId, String receiptId,
                       int units, long version) {}
// Publish only after the guarded reservation decision succeeds.

Cost and verification

Events reduce direct package coupling but add ordering, duplicate and recovery decisions. A persisted registry adds database writes per publication. This sketch is not executed by the source kit.

Common Mistakes

• Do not publish a successful domain event before a valid state change.
• Do not call an in-process event a durable queue.
• Do not assume a broker send rolls back with the database.

Read next

Spring Modulith module APIs: call the inventory root package, not its internals, Spring Modulith module tests: distinguish structure verification from a sliced context, Spring transaction events: run a listener after commit without claiming durability, Spring transactional outbox: commit a receipt and event row together.

Checked publication and remaining delivery

See the in-process event test, then the untested registry recovery boundary.