Deprecate TransactionSynchronizationAdapter

[spring-projects-issues]

Yanming Zhou opened SPR-17190 and commented

Those legacy adapter class should be marked as @Deprecated and removed in the future, such as TransactionSynchronizationAdapter and HandlerInterceptorAdapter.

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No further details from SPR-17190

[spring-projects-issues]

Juergen Hoeller commented

Indeed, those adapter classes are effectively on their way out...

We just didn't feel it was necessary to deprecate them and force people to avoid them or put @SuppressWarnings on their subclasses quite yet. Also, we have a few subclasses ourselves there that we'll have to refactor to straight implementations of the corresponding interface. For the time being, it doesn't hurt to retain assignability to the adapter classes there, just in case somebody makes a corresponding assumption in custom inspection code.

We'll probably do that round of cleanup for 5.2 and remove them altogether in 6.0.

[rstoyanchev]

We missed 5.2 but seems straight-forward enough so let's do it for 5.3.

[sbrannen]

Removal of TransactionSynchronizationAdapter would require people to provide a concrete implementation of getOrder() since Ordered does not provide a default implementation of that method. So, we'd need to document that with the deprecation message.

[sbrannen]

Partially superseded by #25147 regarding HandlerInterceptorAdapter.

[jhoeller]

I've reduced the scope of this ticket for the remaining TransactionSynchronizationAdapter part, potentially making the TransactionSynchronization interface itself extend Ordered (to sort out the migration problem discussed above).

[nickcaballero]

Adding Ordered to the TransactionSynchronization has caused @Order annotations to be ignored in favor of the getOrder result, which by default has been set to LOWEST_PRECEDENCE.

From AnnotationAwareOrderComparator:

	protected Integer findOrder(Object obj) {
		Integer order = super.findOrder(obj); // This uses getOrder()
		if (order != null) {
			return order;
		}
		return findOrderFromAnnotation(obj);
	}

From TransactionSynchronizationManager#getSynchronizations:

	List<TransactionSynchronization> sortedSynchs = new ArrayList<>(synchs);
	AnnotationAwareOrderComparator.sort(sortedSynchs);
	return Collections.unmodifiableList(sortedSynchs);