Persisting entities to both database and search engine
Check out the code from Hibernate Search. It syncs w Lucene and the db at the same time (or async if desired).
Or just use Hibernate Search.
Here is what I did in my former job:
In the service layer, after persisting entity with Hibernate, transform the entity using Jackson and send it to Elasticsearch.Of course, you can do that in the repo layer (DAO Layer) but I don't like it so much.
By the way, if you are using Spring, have a look at the Spring factory Project for Elasticsearch.