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更新时间：2023-06-20 GMT+08:00
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通过Rest High Level Client接入集群

Elasticsearch官方提供了SDK（Rest High level Client）方式连接集群，Rest Client客户端对Elasticsearch的API进行了封装，用户只需要构造对应的结构即可对ES集群进行访问。Rest Client的详细使用请参考官方文档：https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/master/index.html

本文介绍通过Rest High level Client访问CSS集群的配置说明。Rest High level Client接入集群有3种方式：

注意事项

建议Rest High Level Client的版本和Elasticsearch的版本保持一致，例如需要访问的ES集群版本是7.6.2，则使用的Rest High Level Client客户端版本建议也是7.6.2。若您使用相比Elasticsearch集群更高版本的Java Rest High Level Client且存在少量请求的兼容性问题，您可以使用“RestHighLevelClient.getLowLevelClient()”方式直接获取Low Level Client，实现自定义的Elasticsearch请求内容。

准备工作

  • CSS集群处于可用状态。
  • 确保运行Java代码的服务器与CSS集群的网络是互通的。
  • 确认服务器已安装JDK1.8，JDK1.8官网下载地址：http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html。
  • 引入Java依赖。

    其中7.6.2为Elasticsearch Java客户端的版本号。

    • Maven方式引入： 
      <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方式引入： 
      compile group: 'org.elasticsearch.client', name: 'elasticsearch-rest-high-level-client', version: '7.6.2'

通过Rest High Level Client连接非安全集群

通过Rest High Level Client连接非安全集群，并查询test索引是否存在。代码示例如下：

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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;

/**
 * Rest Hive Level 连接非安全集群
 */
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();
    }

    /**
     * constructHttpHosts函数转换host集群节点ip列表。
     */
    public static HttpHost[] constructHttpHosts(List<String> host, int port, String protocol) {
        return host.stream().map(p -> new HttpHost(p, port, protocol)).toArray(HttpHost[]::new);
    }
}

其中，host为集群各个节点的IP地址列表，当存在多个IP地址时，中间用“,”隔开；test为查询的索引名称。

通过Rest High Level Client连接安全集群（不使用安全证书）

该场景适用于连接2种集群：安全模式+HTTP协议的集群、安全模式+HTTPS协议的集群（忽略证书）。

代码示例如下：

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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;

/**
 * Rest High Level连接安全集群（不使用证书）
 */
public class Main {
    /**
     * 创建客户端的类，定义create函数用于创建客户端。
     */
    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;
    }

    /**
     * constructHttpHosts函数转换host集群节点ip列表。
     */
    public static HttpHost[] constructHttpHosts(List<String> host, int port, String protocol) {
        return host.stream().map(p -> new HttpHost(p, port, protocol)).toArray(HttpHost[]::new);
    }

    /**
     * trustAllCerts忽略证书配置。
     */
    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;
        }
    }

    /**
     * main函数参考如下，调用上面的create函数创建客户端，查询“test”索引是否存在。
     */
    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();
    }
}
表1 函数中的变量说明

参数

描述

host

ES集群各个节点（或者独立Client节点）的IP地址列表，当存在多个IP地址时，中间用“,”隔开。

port

ES集群的连接端口，默认是“9200”。

protocol

连接协议，“http”或者“https”，根据集群实际情况填写。

connectTimeout

socket连接超时时间。

connectionRequestTimeout

socket连接请求超时时间。

socketTimeout

socket请求超时时间。

username

访问集群的用户名。

password

用户名对应的密码。

通过Rest High Level Client连接安全集群（使用安全证书）

该场景适用于使用安全证书连接安全模式+HTTPS协议的集群。

  1. 获取安全证书（CloudSearchService.cer）。
    1. 登录云搜索服务控制台。
    2. 选择“集群管理”进入集群列表。
    3. 单击对应集群的名称，进入集群基本信息页面。
    4. 在“基本信息”页面，单击“HTTPS访问”后面的“下载证书”。
  2. 转换安全证书（CloudSearchService.cer）。将下载的安全证书上传到客户端机器上，使用keytool工具将“.cer”证书转换成Java可以读取的“.jks”证书格式。
    • 在Linux系统中，执行如下命令转换证书。 
      keytool -import -alias newname -keystore ./truststore.jks -file ./CloudSearchService.cer
    • 在Windows系统中，执行如下命令转换证书。 
      keytool -import -alias newname -keystore .\truststore.jks -file .\CloudSearchService.cer

    其中，newname是由用户自定义的证书名称。

    该命令执行后，会提示设置证书密码，并确认密码。请保存该密码，后续接入集群会使用。

  3. 接入集群。代码示例如下： 
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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;

/**
 * Rest Hive Level连接安全集群（使用https证书）
 */
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");
            //也可以使用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;
    }

    /**
     * constructHttpHosts函数转换host集群节点ip列表。
     */
    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类定义。
     */
    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];
        }
    }

    /**
     * main函数参考如下，调用上面的create函数创建客户端，查询“test”索引是否存在。
     */
    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();
    }
}
    表2 函数中的参数说明

    参数

    描述

    host

    ES集群各个节点（或者独立Client节点）的IP地址列表，当存在多个IP地址时，中间用“,”隔开。

    port

    ES集群的连接端口，默认是“9200”。

    protocol

    连接协议，此处填写“https”。

    connectTimeout

    socket连接超时时间。

    connectionRequestTimeout

    socket连接请求超时时间。

    socketTimeout

    socket请求超时时间。

    username

    访问集群的用户名。

    password

    用户名对应的密码。

    cerFilePath

    证书路径。

    cerPassword

    证书密码。
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