We now allow externalizing application events to a variety of message brokers through the addition of Spring Modulith modules for Kafka, AMQP and JMS to a user project's classpath. Which events shall be externalized and how they're supposed to be routed to the message broker can be configured through either annotations or via a configuration API declared as Spring bean.
In case Jackson is on the classpath, we also add auto-configuration to use a Boot-configured ObjectMapper instance with the corresponding message broker client APIs to properly serialize and deserialize messages to JSON.
Introduce a new spring-modulith-events-api artifact to contain types that are supposed to be used by application code to deal with event publications. `EventPublication` was moved into that artifact and got everything non infrastructure related extracted from it's previous incarnation. That in turn has been renamed to `TargetEventPublication`.
`CompletedEventPublications` exposes API to allow purging completed publications either by a given predicate or age (in `Duration`). The interface is implemented by `DefaultEventPublicationRegistry` and thus subject for dependency injection into user code. It primarily delegates to the corresponding methods on `EventPublicationRepository` adapting the given `Duration`s to the `Clock` instance already held internally.
`IncompleteEventPublications` allows triggering the re-submission of incomplete publications by the same criteria as `CEP`. The interface is implemented by `PersistentApplicationEventMulticaster` and this subject for dependency injection into user code.
`EventPublicationRepository` now also allows publications to be deleted by identifiers. The existing implementations have been adapted and batch the requests for every 100 identifiers to prevent a list too large to run into limitations of the underlying data store.
Polished transactional metadata declaration in JPA- and MongoDB-based repository implementations.
Tightened nullability expressions here and there.
We now clearly separate between strict configuration, usable via @EnablePersistentDomainEvents and the auto-configuration for EventPublicationRegistry infrastructure. This allows using the core JAR in scenarios, in which no registry functionality is needed.
Changed the EventPublicationRepository interface to allow marking an event as completed without having to materialize it in the first place. This allows us to get rid of CompletableEventPublication. EventPublication not exposes its identifier to make sure the stores can actually store the same id.
Introduced EventPublicationRegistry.deleteCompletedPublicationsOlderThan(Duration) to purge completed event publications before a given point in time.
We now opt out of defining bean definitions for MongoTransactionManager and TransactionTemplate if user defined. We also make sure to run before the EnableTransactionManagementConfiguration to make sure that will see our auto-configured MongoTransactionManager.
As the Event Publication registry only works in transactional environments, we should enable them for MongoDB by default. This will require a replica setup for the MongoDB instance the application interacts with.
AbstractApplicationEventMulticaster.supportsEvent(…) currently doesn't properly match unresolved, generic ApplicationEvents (see [0]). We now work around this problem by additionally matching the raw event types in a custom override of supportsEvent(…).
[0] https://github.com/spring-projects/spring-framework/issues/30399
We now avoid to initialize the EventPublicationRegistry in the ApplicationEventMulticaster unless there is a transactional event listener interested in the event to be published. This should help us avoid premature initialization of the registry for application events published early in the application context bootstrap phase.
