Add AfterLoad lifecycle callback

[goldami1]

Hi,

Following #1159 , I suggest to add additionally to the afterSave, afterConvert and beforeSave callbacks, also the beforeLoad.
Similarly to MongoTemplate which emits AfterLoadEvent before the reader is used to read the document (in ReadDocumentCallback).
Thus, Similar functionality would be apprepciated at the Spring Data EntityCallbacks level for both ES and MONGO.

[sothawo]

Spring Data Elasticsearch does not use events, only callbacks. See https://docs.spring.io/spring-data/elasticsearch/docs/4.3.0/reference/html/#entity-callbacks for information about the events and callbacks. Spring Data MongoDB has both, as there the events were already implemented when the callbacks were introduced.

When adding the callbacks we deliberately did not add the events as well.

[goldami1]

@sothawo that's clear. however, I suggest to add a "beforeLoad" callback invocation right before the Document is read into a domain object. (both for spring-data-mongodb and spring-data-elasticsearch projects)

(for example can be named like: maybeCallAfterLoad(document, type, collectionName))

[sothawo]

If it's only the additional callback, that's fine. I can't speak for Spring DataMongo though, you'll need to add an issue there.

[goldami1]

@sothawo sounds great, will do!
However for spring dataElastic it sounds like a good addition. would appreciate your feedback.

[sothawo]

don't forget to add it to the reactive part as well.

[goldami1]

@sothawo ok. can I help with implementation?

[sothawo]

Sure. Fork the repo, create a branch form main - or use the main branch of your fork, add the necessary tests and implementation (see https://github.com/spring-projects/spring-data-elasticsearch/blob/main/CONTRIBUTING.adoc) and then submit a pull request to have your forked branch be merged into this repo's main.