ESJC is a Java client for using ElasticSearch over the http API.
For notes on the GL setup, see https://wiki.good-loop.com/books/elasticsearch/page/overview
ElasticSearch has an internal Java interface (and indeed, an internal low-level Java client) -- so why have a client library?
- The HTTP API is more stable than the native Java interface.
- Using a native Java client can complicate the task of configuring ElasticSearch.
- The internal interface and client are tightly bound to the cluster configuration and ES version. That can make for real pain (e.g. client code of v8.6 can conflict with a server running v8.5). This client is much more tolerant across version differences.
- This client provides good debug info -- in particular, curl commands you can replay.
Date: Maintaining our own client was better and easier (i.e. the right choice) in 2018 and 2020 (we tried not to do this). The situation has not been re-checked since.
The ESJC master branch tracks the latest stable version of ElasticSearch.
You can get versions of ESJC to match other versions of ElasticSearch in the branches of this repo, names esversion/{number}.
E.g. here is ESJC for ElasticSearch version 2: https://github.com/winterstein/elasticsearch-java-client/tree/esversion/2
Because the http API is fairly stable, the same code usually works across a major version number of ElasticSearch.
The official Java client https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-overview.html This is more tightly bound to the ElasticSearch versioning. The low-level version is very low-level, whilst the high-level version is a work in progress.
JEST: https://github.com/searchbox-io/Jest/tree/master/jest
Comparison: JEST has better coverage of features, whilst ESJC has better multi-thread and async handling, plus support for easier debugging of ES queries. JEST is available via Maven.