Elasticsearch Client for Java: Complete Guide to Working with Java Client

Elasticsearch Client for Java: Complete Guide

Elasticsearch is a powerful distributed search and analytics system built on Apache Lucene. For integration with Java applications, Elastic provides the official Elasticsearch Java Client (formerly known as the High-Level REST Client). In this article, we will thoroughly examine how to use this client for performing basic operations: connection, document indexing, CRUD operations, and full-text search.

What is Elasticsearch Java Client?

Elasticsearch Java Client is a modern, type-safe API for interacting with Elasticsearch from Java. It is built on top of an asynchronous HTTP client and supports all Elasticsearch versions starting from 7.x. Key advantages:

• Full support for all Elasticsearch APIs (indexing, search, aggregations, cluster management).
• Asynchrony and reactivity — built-in support for CompletableFuture and reactive streams.
• Type-safe DSL queries — minimizing errors at compile time.
• Simple configuration — minimal number of dependencies.

Installation and Configuration

To add the client to a Maven project, include the following dependency in pom.xml:

<dependency>    <groupId>co.elastic.clients</groupId>    <artifactId>elasticsearch-java</artifactId>    <version>8.15.0</version></dependency>

For Gradle (build.gradle):

implementation 'co.elastic.clients:elasticsearch-java:8.15.0'

You will also need Jackson for JSON serialization/deserialization:

<dependency>    <groupId>com.fasterxml.jackson.core</groupId>    <artifactId>jackson-databind</artifactId>    <version>2.17.0</version></dependency>

Creating a Client and Connecting

To create a client, you need to specify the Elasticsearch host and port. Example of basic configuration:

import co.elastic.clients.elasticsearch.ElasticsearchClient;import co.elastic.clients.json.jackson.JacksonJsonpMapper;import co.elastic.clients.transport.rest_client.RestClientTransport;import org.apache.http.Header;import org.apache.http.message.BasicHeader;import org.elasticsearch.client.RestClient;

public class ElasticsearchExample {

    public static ElasticsearchClient createClient() {        // Create the Low-Level REST client        RestClient restClient = RestClient.builder(                new HttpHost("localhost", 9200, "http")        ).setDefaultHeaders(new Header[]{                new BasicHeader("Content-Type", "application/json")        }).build();

        // Transport with Jackson mapper        RestClientTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());

        // High-level client        return new ElasticsearchClient(transport);    }

    public static void main(String[] args) throws IOException {        ElasticsearchClient client = createClient();        System.out.println("Client successfully created!");        client.close();    }}

Working with Indices

Before starting work, you need to create an index. Let's look at an example of creating an index with a mapping:

public static void createIndex(ElasticsearchClient client, String indexName) throws IOException {    client.indices().create(c -> c            .index(indexName)            .mappings(m -> m                    .properties("title", p -> p.text(t -> t))                    .properties("content", p -> p.text(t -> t))                    .properties("price", p -> p.double_(d -> d))                    .properties("createdAt", p -> p.date(d -> d))