Learn How to connect to an OpenSearch Cluster with Java

Connect to an OpenSearch Cluster with Java

This sample app was created and tested with

java version "23.0.2" 2025-01-21
Apache Maven 3.9.8 (36645f6c9b5079805ea5009217e36f2cffd34256)

This article assumes that you have already created an OpenSearch Cluster, if you have not yet done this then please see this guide to create to create a cluster:

Creating an OpenSearch Cluster

Here's a Python example of sending logs to OpenSearch, this example uses the OpenSearch Java Client (org.opensearch.client:opensearch-java) and integrates it with the logging framework SLF4J.

This guide is created using Maven.

Create Project

Create a new Maven project:

mvn archetype:generate -DgroupId=com.example -DartifactId=OpenSearchLogger -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Navigate into the project directory of your new project.

cd OpenSearchLogger

Add Dependencies

Open your pom.xml file and copy the following over the existing content.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.example</groupId>
    <artifactId>OpenSearchLogger</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>OpenSearchLogger</name>
    <url>http://maven.apache.org</url>
    <dependencies>
        <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>3.8.1</version>
        <scope>test</scope>
        </dependency>
        <!-- OpenSearch High-Level REST Client -->
            <dependency>
                <groupId>org.opensearch.client</groupId>
                <artifactId>opensearch-rest-high-level-client</artifactId>
                <version>2.9.0</version> <!-- Update version if needed -->
            </dependency>
 
            <!-- Apache HTTP Components (Required for Basic Authentication) -->
            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.13</version> <!-- Update version if needed -->
            </dependency>
 
            <!-- SLF4J for Logging -->
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
                <version>2.0.9</version> <!-- Update version if needed -->
            </dependency>
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-simple</artifactId>
                <version>2.0.9</version> <!-- Update version if needed -->
            </dependency>
 
    </dependencies>
    
    <build>
        <plugins>
            <!-- Maven Shade Plugin to create an executable JAR -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.1</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <!-- Add the main class to the JAR manifest -->
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>com.example.App</mainClass> <!-- Replace with your main class -->
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
    </project>

Save the file and then run the following command.

mvn clean install

Java Code Example

Replace the contents of src/main/java/com/example/App.java with the following code:

App.java

package com.example;
 
import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.opensearch.client.RequestOptions;
import org.opensearch.client.RestClient;
import org.opensearch.client.RestHighLevelClient;
import org.opensearch.action.index.IndexRequest;
import org.opensearch.action.index.IndexResponse;
import org.opensearch.common.xcontent.XContentType;
 
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
 
public class App {
    public static void main(String[] args) {
        // OpenSearch endpoint configuration
        String hostname = "@opensearch.endpointAddress:9200";
        String username = "@opensearch.username";
        String password = "@opensearch.password";
 
        // Set up authentication
        BasicCredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
 
        // Create OpenSearch client
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(HttpHost.create(hostname))
                        .setHttpClientConfigCallback(
                                httpClientBuilder -> httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider)
                        )
        );
 
        // Create a daily log index name
        String indexName = "logit-example-" + LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy.MM.dd"));
 
        // Prepare a sample log entry
        String logMessage = "{"
                + "\"@timestamp\":\"" + LocalDateTime.now() + "\","
                + "\"level\":\"INFO\","
                + "\"message\":\"This is a log message from Java\","
                + "\"service\":\"logit-service\""
                + "}";
 
        try {
            // Create and send an index request
            IndexRequest request = new IndexRequest(indexName)
                    .source(logMessage, XContentType.JSON);
            IndexResponse response = client.index(request, RequestOptions.DEFAULT);
 
            // Log the response
            System.out.println("Log indexed successfully. ID: " + response);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            // Close the client
            try {
                client.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Create a new file called Utils.java in the same folder as App.java. Copy the following code and save the file.

Utils.java

package com.example;
 
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.impl.client.BasicCredentialsProvider;
 
public class Utils {
    /**
     * Creates a BasicCredentialsProvider for OpenSearch authentication.
     *
     * @param username the username for authentication
     * @param password the password for authentication
     * @return a BasicCredentialsProvider with the provided credentials
     */
    public static BasicCredentialsProvider getCredentialsProvider(String username, String password) {
        BasicCredentialsProvider provider = new BasicCredentialsProvider();
        provider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
        return provider;
    }
}

Key Points

Ensure all required dependencies are correctly installed.

Properly handle exceptions for production use, e.g., retry logic for failed requests.

Build and Run the Application

Build the project with the following command.

mvn clean package

Run the application to send logs to hosted Opensearch.

java -cp target/OpenSearchLogger-1.0-SNAPSHOT.jar com.example.App

Further Help and Guidance

See the articles below for further help and guidance as a next step: