Updated on 2025-09-05 GMT+08:00

Accessing an Elasticsearch Cluster Through the High Level REST Client

Elasticsearch provides SDK (High Level REST Client) for connecting to a cluster. This client encapsulates Elasticsearch APIs. You only need to construct required structures to access the Elasticsearch cluster. For details about how to use the Rest Client, see the official document at https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high.html.

This section describes how to use the High Level REST Client to access a CSS cluster. The High Level REST Client can be connected to the cluster in one of the following ways:

Constraints

The High Level REST Client version should match the Elasticsearch version. For example, use High Level REST Client 7.6.2 to access an Elasticsearch 7.6.2 cluster. If your Java High Level REST Client version is later than the Elasticsearch cluster and there are incompatibility issues with a few requests, you can use RestHighLevelClient.getLowLevelClient() to obtain Low Level Client and customize the Elasticsearch request content.

Prerequisites

  • There are available CSS clusters.
  • You have a server running Java that can communicate with the CSS cluster.
  • Depending on the network configuration method used, obtain the cluster access address. For details, see Network Configuration.
  • Install JDK 1.8 on the server. You can download JDK 1.8 from: https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
  • Java dependencies have been installed on the server.

    7.6.2 indicates the version of the Elasticsearch Java client.

    • Maven mode:
      <dependency>
          <groupId>org.elasticsearch.client</groupId>
          <artifactId>elasticsearch-rest-high-level-client</artifactId>
          <version>7.6.2</version>
      </dependency>
      <dependency>
          <groupId>org.elasticsearch</groupId>
          <artifactId>elasticsearch</artifactId>
          <version>7.6.2</version>
      </dependency>
    • Gradle mode:
      compile group: 'org.elasticsearch.client', name: 'elasticsearch-rest-high-level-client', version: '7.6.2'

Connecting to a Non-Security Mode Cluster Through the High Level REST Client

Use the High Level REST Client to connect to a non-security mode cluster and check whether the test index exists. The sample code is as follows:

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import org.apache.http.HttpHost;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;

import java.io.IOException;
import java.util.Arrays;
import java.util.List;

/**
* Use Rest Hive Level to connect to a non-security cluster.
 */
public class Main {
    public static void main(String[] args) throws IOException {
        List<String> host = Arrays.asList("xx.xx.xx.xx", "xx.xx.xx.xx");
        RestClientBuilder builder = RestClient.builder(constructHttpHosts(host, 9200, "http"));
        final RestHighLevelClient client = new RestHighLevelClient(builder);
        GetIndexRequest indexRequest = new GetIndexRequest("test");
        boolean exists = client.indices().exists(indexRequest, RequestOptions.DEFAULT);
        System.out.println(exists);
        client.close();
    }

    /**
     * Use the constructHttpHosts function to convert the node IP address list of the host cluster.
     */
    public static HttpHost[] constructHttpHosts(List<String> host, int port, String protocol) {
        return host.stream().map(p -> new HttpHost(p, port, protocol)).toArray(HttpHost[]::new);
    }
}

host indicates the IP address of the cluster. If there are multiple IP addresses, separate them using commas (,). test indicates the index name to be queried.

Connecting to a Security-Mode Cluster Through High Level REST Client (Without a Security Certificate)

Connect to a security-mode cluster that uses either HTTP or HTTPS without using a security certificate.

The sample code is as follows:

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import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.apache.http.nio.conn.ssl.SSLIOSessionStrategy;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.admin.cluster.health.ClusterHealthRequest;
import org.elasticsearch.action.admin.cluster.health.ClusterHealthResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.Nullable;

import java.io.IOException;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

/**
* Connect to a security cluster through Rest High Level (without using certificates).
 */
public class Main {
    /**
* Create a class for the client. Define the create function.
     */
    public static RestHighLevelClient create(List<String> host, int port, String protocol, int connectTimeout, int connectionRequestTimeout, int socketTimeout, String username, String password) throws IOException{
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
        SSLContext sc = null;
        try {
            sc = SSLContext.getInstance("SSL");
            sc.init(null, trustAllCerts, new SecureRandom());
        } catch (KeyManagementException | NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        SSLIOSessionStrategy sessionStrategy = new SSLIOSessionStrategy(sc, new NullHostNameVerifier());
        SecuredHttpClientConfigCallback httpClientConfigCallback = new SecuredHttpClientConfigCallback(sessionStrategy,
            credentialsProvider);


        RestClientBuilder builder = RestClient.builder(constructHttpHosts(host, port, protocol))
            .setRequestConfigCallback(requestConfig -> requestConfig.setConnectTimeout(connectTimeout)
                .setConnectionRequestTimeout(connectionRequestTimeout)
                .setSocketTimeout(socketTimeout))
            .setHttpClientConfigCallback(httpClientConfigCallback);
        final RestHighLevelClient client = new RestHighLevelClient(builder);
        logger.info("es rest client build success {} ", client);

        ClusterHealthRequest request = new ClusterHealthRequest();
        ClusterHealthResponse response = client.cluster().health(request, RequestOptions.DEFAULT);
        logger.info("es rest client health response {} ", response);
        return client;
    }

    /**
     * Use the constructHttpHosts function to convert the node IP address list of the host cluster.
     */
    public static HttpHost[] constructHttpHosts(List<String> host, int port, String protocol) {
        return host.stream().map(p -> new HttpHost(p, port, protocol)).toArray(HttpHost[]::new);
    }

    /**
     * Configure trustAllCerts to ignore the certificate configuration.
     */
    public static TrustManager[] trustAllCerts = new TrustManager[] {
        new X509TrustManager() {
            @Override
            public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            @Override
            public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return null;
            }
        }
    };

    private static final Logger logger = LogManager.getLogger(Main.class);

    static class SecuredHttpClientConfigCallback implements RestClientBuilder.HttpClientConfigCallback {
        @Nullable
        private final CredentialsProvider credentialsProvider;
        /**
         * The {@link SSLIOSessionStrategy} for all requests to enable SSL / TLS encryption.
         */
        private final SSLIOSessionStrategy sslStrategy;
        /**
         * Create a new {@link SecuredHttpClientConfigCallback}.
         *
         * @param credentialsProvider The credential provider, if a username/password have been supplied
         * @param sslStrategy         The SSL strategy, if SSL / TLS have been supplied
         * @throws NullPointerException if {@code sslStrategy} is {@code null}
         */
        SecuredHttpClientConfigCallback(final SSLIOSessionStrategy sslStrategy,
            @Nullable final CredentialsProvider credentialsProvider) {
            this.sslStrategy = Objects.requireNonNull(sslStrategy);
            this.credentialsProvider = credentialsProvider;
        }
        /**
         * Get the {@link CredentialsProvider} that will be added to the HTTP client.
         *
         * @return Can be {@code null}.
         */
        @Nullable
        CredentialsProvider getCredentialsProvider() {
            return credentialsProvider;
        }
        /**
         * Get the {@link SSLIOSessionStrategy} that will be added to the HTTP client.
         *
         * @return Never {@code null}.
         */
        SSLIOSessionStrategy getSSLStrategy() {
            return sslStrategy;
        }
        /**
         * Sets the {@linkplain HttpAsyncClientBuilder#setDefaultCredentialsProvider(CredentialsProvider) credential provider},
         *
         * @param httpClientBuilder The client to configure.
         * @return Always {@code httpClientBuilder}.
         */
        @Override
        public HttpAsyncClientBuilder customizeHttpClient(final HttpAsyncClientBuilder httpClientBuilder) {
            // enable SSL / TLS
            httpClientBuilder.setSSLStrategy(sslStrategy);
            // enable user authentication
            if (credentialsProvider != null) {
                httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
            }
            return httpClientBuilder;
        }
    }

    public static class NullHostNameVerifier implements HostnameVerifier {
        @Override
        public boolean verify(String arg0, SSLSession arg1) {
            return true;
        }
    }

    /**
* The following is an example of the main function. Call the create function to create a client and check whether the test index exists.
     */
    public static void main(String[] args) throws IOException {
        RestHighLevelClient client = create(Arrays.asList("xx.xx.xx.xx", "xx.xx.xx.xx"), 9200, "https", 1000, 1000, 1000,  "username", "password");
        GetIndexRequest indexRequest = new GetIndexRequest("test");
        boolean exists = client.indices().exists(indexRequest, RequestOptions.DEFAULT);
        System.out.println(exists);
        client.close();
    }
}
Table 1 Variables

Parameter

Description

host

IP address for accessing the Elasticsearch cluster. If there are multiple IP addresses, separate them with commas (,).

port

Access port of the Elasticsearch cluster. The default value is 9200.

protocol

Connection protocol, which can be http or https.

connectTimeout

Socket connection timeout (in ms).

connectionRequestTimeout

Socket connection request timeout (in ms).

socketTimeout

Socket request timeout (in ms).

username

Username for accessing the cluster.

password

Password of the user.

Connecting to a Security-Mode Cluster Through High Level REST Client (With a Security Certificate)

Connect to a security-mode Elasticsearch cluster that uses HTTPS using a security certificate. The sample code is as follows:

For how to obtain and upload a security certificate, see Obtaining and Uploading a Security Certificate.

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import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.conn.ssl.NoopHostnameVerifier;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.apache.http.nio.conn.ssl.SSLIOSessionStrategy;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.admin.cluster.health.ClusterHealthRequest;
import org.elasticsearch.action.admin.cluster.health.ClusterHealthResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.common.Nullable;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.KeyStore;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

/**
* Use Rest Hive Level to connect to a security cluster (using an HTTPS certificate).
 */
public class Main {
    public static RestHighLevelClient create(List<String> host, int port, String protocol, int connectTimeout, int connectionRequestTimeout, int socketTimeout, String username, String password, String certFilePath,
        String certPassword) throws IOException {

        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
        SSLContext sc = null;
        try {
            TrustManager[] tm = {new MyX509TrustManager(certFilePath, certPassword)};
            sc = SSLContext.getInstance("SSL", "SunJSSE");
            //You can also use SSLContext sslContext = SSLContext.getInstance("TLSv1.2");
            sc.init(null, tm, new SecureRandom());
        } catch (Exception e) {
            e.printStackTrace();
        }

        SSLIOSessionStrategy sessionStrategy = new SSLIOSessionStrategy(sc, new NoopHostnameVerifier());
        SecuredHttpClientConfigCallback httpClientConfigCallback = new SecuredHttpClientConfigCallback(sessionStrategy,
            credentialsProvider);

        RestClientBuilder builder = RestClient.builder(constructHttpHosts(host, port, protocol))
            .setRequestConfigCallback(requestConfig -> requestConfig.setConnectTimeout(connectTimeout)
                .setConnectionRequestTimeout(connectionRequestTimeout)
                .setSocketTimeout(socketTimeout))
            .setHttpClientConfigCallback(httpClientConfigCallback);
        final RestHighLevelClient client = new RestHighLevelClient(builder);
        logger.info("es rest client build success {} ", client);

        ClusterHealthRequest request = new ClusterHealthRequest();
        ClusterHealthResponse response = client.cluster().health(request, RequestOptions.DEFAULT);
        logger.info("es rest client health response {} ", response);
        return client;
    }

    /**
     * Use the constructHttpHosts function to convert the node IP address list of the host cluster.
     */
    public static HttpHost[] constructHttpHosts(List<String> host, int port, String protocol) {
        return host.stream().map(p -> new HttpHost(p, port, protocol)).toArray(HttpHost[]::new);
    }

    /**
     * SecuredHttpClientConfigCallback class definition
     */
    static class SecuredHttpClientConfigCallback implements RestClientBuilder.HttpClientConfigCallback {
        @Nullable
        private final CredentialsProvider credentialsProvider;

        private final SSLIOSessionStrategy sslStrategy;

        SecuredHttpClientConfigCallback(final SSLIOSessionStrategy sslStrategy,
            @Nullable final CredentialsProvider credentialsProvider) {
            this.sslStrategy = Objects.requireNonNull(sslStrategy);
            this.credentialsProvider = credentialsProvider;
        }

        @Nullable
        CredentialsProvider getCredentialsProvider() {
            return credentialsProvider;
        }

        SSLIOSessionStrategy getSSLStrategy() {
            return sslStrategy;
        }

        @Override
        public HttpAsyncClientBuilder customizeHttpClient(final HttpAsyncClientBuilder httpClientBuilder) {
            httpClientBuilder.setSSLStrategy(sslStrategy);
            if (credentialsProvider != null) {
                httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
            }
            return httpClientBuilder;
        }
    }

    private static final Logger logger = LogManager.getLogger(Main.class);

    public static class MyX509TrustManager implements X509TrustManager {
        X509TrustManager sunJSSEX509TrustManager;

        MyX509TrustManager(String certFilePath, String certPassword) throws Exception {
            File file = new File(certFilePath);
            if (!file.isFile()) {
                throw new Exception("Wrong Certification Path");
            }
            System.out.println("Loading KeyStore " + file + "...");
            InputStream in = new FileInputStream(file);
            KeyStore ks = KeyStore.getInstance("JKS");
            ks.load(in, certPassword.toCharArray());
            TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509", "SunJSSE");
            tmf.init(ks);
            TrustManager[] tms = tmf.getTrustManagers();
            for (TrustManager tm : tms) {
                if (tm instanceof X509TrustManager) {
                    sunJSSEX509TrustManager = (X509TrustManager) tm;
                    return;
                }
            }
            throw new Exception("Couldn't initialize");
        }

        @Override
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {

        }

        @Override
        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {

        }

        @Override
        public X509Certificate[] getAcceptedIssuers() {
            return new X509Certificate[0];
        }
    }

    /**
* The following is an example of the main function. Call the create function to create a client and check whether the test index exists.
     */
    public static void main(String[] args) throws IOException {
        RestHighLevelClient client = create(Arrays.asList("xxx.xxx.xxx.xxx", "xxx.xxx.xxx.xxx"), 9200, "https", 1000, 1000, 1000, "username", "password", "certFilePath", "certPassword");
        GetIndexRequest indexRequest = new GetIndexRequest("test");
        boolean exists = client.indices().exists(indexRequest, RequestOptions.DEFAULT);
        System.out.println(exists);
        client.close();
    }
}
Table 2 Function parameters

Parameter

Description

host

IP address for accessing the Elasticsearch cluster. If there are multiple IP addresses, separate them with commas (,).

port

Access port of the Elasticsearch cluster. The default value is 9200.

protocol

Connection protocol. Set this parameter to https.

connectTimeout

Socket connection timeout (in ms).

connectionRequestTimeout

Socket connection request timeout (in ms).

socketTimeout

Socket request timeout (in ms).

username

Username for accessing the cluster.

password

Password of the user.

certFilePath

Certificate path.

certPassword

Certificate password.

Obtaining and Uploading a Security Certificate

To access a security-mode Elasticsearch cluster that uses HTTPS, a security certificate must be loaded. Perform the following steps to obtain the security certificate and upload it to the client:

  1. Obtain the security certificate CloudSearchService.cer.
    1. Log in to the CSS management console.
    2. In the navigation pane on the left, choose Clusters > Elasticsearch.
    3. In the cluster list, click the name of the target cluster. The cluster information page is displayed.
    4. Click the Overview tab. In the Configuration area, click Download Certificate next to HTTPS Access.
      Figure 1 Downloading a security certificate
  2. Convert the security certificate CloudSearchService.cer. Upload the downloaded security certificate to the client and use keytool to convert the .cer certificate into a .jks certificate that can be read by Java.
    • In Linux, run the following command to convert the certificate:
      keytool -import -alias newname -keystore ./truststore.jks -file ./CloudSearchService.cer 
    • In Windows, run the following command to convert the certificate:
      keytool -import -alias newname -keystore .\truststore.jks -file .\CloudSearchService.cer

    In the preceding command, newname indicates the user-defined certificate name.

    After this command is executed, you will be prompted to set the certificate password and confirm the password. Securely store the password. It will be used for accessing the cluster.