So I basically just create an ElasticSearch bean (DAO) and couple it within my EntityService class. Whenever I create a new Entity, I'll also create it within ElasticSearch itself. So for each record in my SQL table, there's a coexisting document within Elasticsearch. This is better than an ETL as I get realtime searching.
One more question: if someone is building a service from the ground up and wants to incorporate elasticsearch, do they do the same thing (if they're sticking to a SQL database)? This guide is extremely helpful, by the way.