SPR-12756: Local visibility for writes to caches with transactional decorators

[williamhoyle]

This patch adds an alternative to the TransactionAwareCacheDecorator that addresses issues raised in SPR-12756 - it makes writes to decorated caches visible within the scope of the transaction.

It is intended to be minimally obtrusive. The current interface is not changed beyond adding a setCacheDecoratorFactory method to the TransactionAwareCacheManagerProxy to allow the strategy to be selected. The behaviour defaults to use the existing TransactionAwareCacheDecorator.

[neiser]

@williamhoyle I found this PR while starting from this StackOverflow question asking why no CacheErrorHandler is called when transaction support is enabled for caching. This is IMHO a shortcoming if not a bug in Spring's way of "transaction-aware caching".

Now I found also this little project: https://github.com/ethlo/spring-tx-cache-decorator by @ethlo. Have you been aware of this project when you implemented this PR?

Do you think this PR could be extended to cover also the missing CacheErrorHandler call?

[snicoll]

Looking at the history of this issue (and #16574), it looks like that https://github.com/ethlo/spring-tx-cache-decorator could supersede this unless we decide we want to support that in the core framework and handle the additional complexity.

[neiser]

@snicoll I don't see directly how #16574 is related to this issue, but if transaction-aware caches are part of the Spring framework or not should really be decided as right now it is not consistently implemented. So either fix or remove 😀

[snicoll]

Reviewing the history of this issue, I am not keen to bring that extra complexity and layering in the cache abstraction, so I am going to close this now. The discussion in #17353 provides additional context and justification. Thanks for the PR, in any case!