Accessing a Cluster Through the Rest High Level Client

Precautions

You are advised to use the Rest High Level Client version that matches the Elasticsearch version. For example, use Rest High Level Client 7.6.2 to access the Elasticsearch cluster 7.6.2. If your Java Rest High Level Client version is later than the Elasticsearch cluster and incompatible with a few requests, you can use RestHighLevelClient.getLowLevelClient() to obtain Low Level Client and customize the Elasticsearch request content.

Prerequisites

• The CSS cluster is available.
• Ensure that the server running Java can communicate with the CSS cluster.
• 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
• Declare Java dependencies.

  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 Cluster Through the Rest High Level Client

You can use the Rest High Level Client to connect to a non-security 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("x.x.x.x", "x.x.x.x");
        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 list of each node in the cluster. If there are multiple IP addresses, separate them with commas (,). test indicates the index name to be queried.

Connecting to a Security Cluster Through Rest High Level Client (Without Security Certificates)

You can connect to a cluster in security mode+HTTP or a cluster in security mode + HTTPS (without using certificates).

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("x.x.x.x", "x.x.x.x"), 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();
    }
}

Connecting to a Security Cluster Through Rest High Level Client (With Security Certificates)

You can use a security certificate to connect to a cluster in security mode + HTTPS.

1. Obtain the security certificate CloudSearchService.cer.
   1. Log in to the CSS management console.
   2. In the navigation pane, choose Clusters. The cluster list is displayed.
   3. Click the name of a cluster to go to the cluster details page.
   4. On the Configuration page, click Download Certificate next to HTTPS Access.
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.

3. Access the cluster. 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.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 cerFilePath, String cerPassword) throws IOException { final CredentialsProvider credentialsProvider = new BasicCredentialsProvider(); credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password)); SSLContext sc = null; try { TrustManager[] tm = {new MyX509TrustManager(cerFilePath, cerPassword)}; 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 cerFilePath, String cerPassword) throws Exception { File file = new File(cerFilePath); 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, cerPassword.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", "cerFilePath", "cerPassword"); GetIndexRequest indexRequest = new GetIndexRequest("test"); boolean exists = client.indices().exists(indexRequest, RequestOptions.DEFAULT); System.out.println(exists); client.close(); } }

   Table 2 Function parameters

   Name	Description
   host	List of the IP addresses of Elasticsearch nodes (or independent Client node). Multiple IP addresses are separated using 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 period.
   connectionRequestTimeout	Timeout period of a socket connection request.
   socketTimeout	Timeout period of a socket request.
   username	Username for accessing the cluster.
   password	Password of the user.
   cerFilePath	Certificate path.
   cerPassword	Certificate password.