Introduction
Elasticsearch functionalities can be easily integrated in any Java application in several ways, both via a REST API and native ones.
In Java it's easy to call a REST HTTP interface with one of the many of libraries available, such as the Apache HttpComponents client http://hc.apache.org/. In this field there's no such thing as the most used library; typically, developers choose the library that best suits their preferences or that they know very well.
Each JVM language can also use the native protocol (discussed in C) to integrate Elasticsearch with their applications.
Chapter 1, Getting Started is one of the faster protocols available to communicate with Elasticsearch due to many factors such as its binary nature, its fast native serializer or deserializer of the data, its asynchronous approach to communicating, and the hop reduction (native client nodes are able to communicate directly with the node that contains the data without executing the double hop needed in REST calls...