Elasticsearch 入门实战(4)–Java Low Level REST Client 使用

本文主要介绍 Elasticsearch Java Low Level REST Client 的使用，相关的环境及软件信息如下：CentOS 7.6.1810、Java 1.8.0_321(客户端用)、Elasticsearch 8.2.2。

1、Java Low Level REST Client 的特点

• minimal dependencies
• load balancing across all available nodes
• failover in case of node failures and upon specific response codes
• failed connection penalization (whether a failed node is retried depends on how many consecutive times it failed; the more failed attempts the longer the client will wait before trying that same node again)
• persistent connections
• trace logging of requests and responses
• optional automatic discovery of cluster nodes

2、引入依赖

<dependency>
    <groupId>org.elasticsearch.clientgroupId>
    <artifactId>elasticsearch-rest-clientartifactId>
    <version>8.2.2version>
dependency>

3、使用

Java Low Level REST Client 主要工作是组装 JSON 格式的请求数据，其他都是些通用的配置；请求数据的详细说明可参考：Elasticsearch 入门实战(3)–REST API 使用。

3.1、Elasticsearch 关闭了安全认证，使用 HTTP 协议访问

@Test
public void http() {
    RestClient restClient = null;
    try {
        RestClientBuilder builder = RestClient.builder(
                new HttpHost("10.49.196.10", 9200),
                new HttpHost("10.49.196.11", 9200),
                new HttpHost("10.49.196.12", 9200));
        //设置失败监听器
        builder.setFailureListener(new RestClient.FailureListener() {
            @Override
            public void onFailure(Node node) {
                logger.info("失败:node={}", node);
            }
        });
        //设置请求头
        Header[] defaultHeaders = new Header[]{new BasicHeader("head-a", "123")};
        builder.setDefaultHeaders(defaultHeaders);

        //设置节点选择器
        builder.setNodeSelector(NodeSelector.SKIP_DEDICATED_MASTERS);

        //设置请求配置回调方法
        builder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
            @Override
            public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder builder) {
                return builder.setSocketTimeout(1000 * 5);
            }
        });

        //用户名密码
        CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("elastic", "123456"));
        //设置HttpClient配置回调方法
        builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
            @Override
            public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpAsyncClientBuilder) {
                return httpAsyncClientBuilder.setUserAgent("elasticseatch-rest-client").setDefaultCredentialsProvider(credentialsProvider);
            }
        });
        restClient = builder.build();

        //请求对象
        Request request = new Request("GET", "/poet-index/_search");
        request.addParameter("pretty", "true");
        //请求体，json数据
        String body = "{\n" +
                "  \"query\": {\n" +
                "    \"match\": {\n" +
                "      \"success\": \"思想\"\n" +
                "    }\n" +
                "  },\n" +
                "  \"from\": 0,\n" +
                "  \"size\": 10\n" +
                "}";
        request.setEntity(new NStringEntity(body, ContentType.APPLICATION_JSON));
        Response response = restClient.performRequest(request);
        logger.info("requestLine={}", response.getRequestLine());
        logger.info("host={}", response.getHost());
        logger.info("statusCode={}", response.getStatusLine().getStatusCode());
        logger.info("headers={}", response.getHeaders());
        logger.info("responseBody={}", EntityUtils.toString(response.getEntity()));
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (restClient != null) {
            try {
                restClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

3.2、Elasticsearch 开启了安全认证，使用 HTTPS 协议访问

@Test
public void https() {
    RestClient restClient = null;
    try {
        RestClientBuilder builder = RestClient.builder(
                new HttpHost("10.49.196.10", 9200, "https"),
                new HttpHost("10.49.196.11", 9200, "https"),
                new HttpHost("10.49.196.12", 9200, "https"));
        //设置失败监听器
        builder.setFailureListener(new RestClient.FailureListener() {
            @Override
            public void onFailure(Node node) {
                logger.info("失败:node={}", node);
            }
        });
        //设置请求头
        Header[] defaultHeaders = new Header[]{new BasicHeader("head-a", "123")};
        builder.setDefaultHeaders(defaultHeaders);

        //设置节点选择器
        builder.setNodeSelector(NodeSelector.SKIP_DEDICATED_MASTERS);

        //设置请求配置回调方法
        builder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
            @Override
            public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder builder) {
                return builder.setSocketTimeout(1000 * 5);
            }
        });

        //用户名密码
        CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("elastic", "123456"));
        //设置HttpClient配置回调方法
        builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
            @Override
            public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpAsyncClientBuilder) {
                return httpAsyncClientBuilder.setUserAgent("elasticseatch-rest-client")
                        .setDefaultCredentialsProvider(credentialsProvider)
                        .setSSLContext(getSSLContext());
            }
        });
        restClient = builder.build();

        //请求对象
        Request request = new Request("GET", "/poet-index/_search");
        request.addParameter("pretty", "true");
        //请求体，json数据
        String body = "{\n" +
                "  \"query\": {\n" +
                "    \"match\": {\n" +
                "      \"success\": \"思想\"\n" +
                "    }\n" +
                "  },\n" +
                "  \"from\": 0,\n" +
                "  \"size\": 10\n" +
                "}";
        request.setEntity(new NStringEntity(body, ContentType.APPLICATION_JSON));
        Response response = restClient.performRequest(request);
        logger.info("requestLine={}", response.getRequestLine());
        logger.info("host={}", response.getHost());
        logger.info("statusCode={}", response.getStatusLine().getStatusCode());
        logger.info("headers={}", response.getHeaders());
        logger.info("responseBody={}", EntityUtils.toString(response.getEntity()));
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (restClient != null) {
            try {
                restClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

3.3、完整代码

package com.abc.demo.es;

import org.apache.http.Header;
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.client.config.RequestConfig;
import org.apache.http.conn.ssl.TrustAllStrategy;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.apache.http.message.BasicHeader;
import org.apache.http.nio.entity.NStringEntity;
import org.apache.http.ssl.SSLContextBuilder;
import org.apache.http.ssl.SSLContexts;
import org.apache.http.util.EntityUtils;
import org.elasticsearch.client.*;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.net.ssl.SSLContext;
import java.io.IOException;

public class ElasticseatchRestClientCase {
    private static final Logger logger = LoggerFactory.getLogger(ElasticseatchRestClientCase.class.getName());

    @Test
    public void http() {
        RestClient restClient = null;
        try {
            RestClientBuilder builder = RestClient.builder(
                    new HttpHost("10.49.196.10", 9200),
                    new HttpHost("10.49.196.11", 9200),
                    new HttpHost("10.49.196.12", 9200));
            //设置失败监听器
            builder.setFailureListener(new RestClient.FailureListener() {
                @Override
                public void onFailure(Node node) {
                    logger.info("失败:node={}", node);
                }
            });
            //设置请求头
            Header[] defaultHeaders = new Header[]{new BasicHeader("head-a", "123")};
            builder.setDefaultHeaders(defaultHeaders);

            //设置节点选择器
            builder.setNodeSelector(NodeSelector.SKIP_DEDICATED_MASTERS);

            //设置请求配置回调方法
            builder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
                @Override
                public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder builder) {
                    return builder.setSocketTimeout(1000 * 5);
                }
            });

            //用户名密码
            CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("elastic", "123456"));
            //设置HttpClient配置回调方法
            builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
                @Override
                public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpAsyncClientBuilder) {
                    return httpAsyncClientBuilder.setUserAgent("elasticseatch-rest-client").setDefaultCredentialsProvider(credentialsProvider);
                }
            });
            restClient = builder.build();

            //请求对象
            Request request = new Request("GET", "/poet-index/_search");
            request.addParameter("pretty", "true");
            //请求体，json数据
            String body = "{\n" +
                    "  \"query\": {\n" +
                    "    \"match\": {\n" +
                    "      \"success\": \"思想\"\n" +
                    "    }\n" +
                    "  },\n" +
                    "  \"from\": 0,\n" +
                    "  \"size\": 10\n" +
                    "}";
            request.setEntity(new NStringEntity(body, ContentType.APPLICATION_JSON));
            Response response = restClient.performRequest(request);
            logger.info("requestLine={}", response.getRequestLine());
            logger.info("host={}", response.getHost());
            logger.info("statusCode={}", response.getStatusLine().getStatusCode());
            logger.info("headers={}", response.getHeaders());
            logger.info("responseBody={}", EntityUtils.toString(response.getEntity()));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (restClient != null) {
                try {
                    restClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Test
    public void https() {
        RestClient restClient = null;
        try {
            RestClientBuilder builder = RestClient.builder(
                    new HttpHost("10.49.196.10", 9200, "https"),
                    new HttpHost("10.49.196.11", 9200, "https"),
                    new HttpHost("10.49.196.12", 9200, "https"));
            //设置失败监听器
            builder.setFailureListener(new RestClient.FailureListener() {
                @Override
                public void onFailure(Node node) {
                    logger.info("失败:node={}", node);
                }
            });
            //设置请求头
            Header[] defaultHeaders = new Header[]{new BasicHeader("head-a", "123")};
            builder.setDefaultHeaders(defaultHeaders);

            //设置节点选择器
            builder.setNodeSelector(NodeSelector.SKIP_DEDICATED_MASTERS);

            //设置请求配置回调方法
            builder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
                @Override
                public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder builder) {
                    return builder.setSocketTimeout(1000 * 5);
                }
            });

            //用户名密码
            CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("elastic", "123456"));
            //设置HttpClient配置回调方法
            builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
                @Override
                public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpAsyncClientBuilder) {
                    return httpAsyncClientBuilder.setUserAgent("elasticseatch-rest-client")
                            .setDefaultCredentialsProvider(credentialsProvider)
                            .setSSLContext(getSSLContext());
                }
            });
            restClient = builder.build();

            //请求对象
            Request request = new Request("GET", "/poet-index/_search");
            request.addParameter("pretty", "true");
            //请求体，json数据
            String body = "{\n" +
                    "  \"query\": {\n" +
                    "    \"match\": {\n" +
                    "      \"success\": \"思想\"\n" +
                    "    }\n" +
                    "  },\n" +
                    "  \"from\": 0,\n" +
                    "  \"size\": 10\n" +
                    "}";
            request.setEntity(new NStringEntity(body, ContentType.APPLICATION_JSON));
            Response response = restClient.performRequest(request);
            logger.info("requestLine={}", response.getRequestLine());
            logger.info("host={}", response.getHost());
            logger.info("statusCode={}", response.getStatusLine().getStatusCode());
            logger.info("headers={}", response.getHeaders());
            logger.info("responseBody={}", EntityUtils.toString(response.getEntity()));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (restClient != null) {
                try {
                    restClient.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    private SSLContext getSSLContext() {
        try {
            SSLContextBuilder bulider = SSLContexts.custom();
            bulider.loadTrustMaterial(new TrustAllStrategy());
            return bulider.build();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

}

ElasticseatchRestClientCase.java

详细的 Elasticsearch Java Low Level REST Client 使用说明，看参考官网文档：https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/current/java-rest-low.html。

Original: https://www.cnblogs.com/wuyongyin/p/16395987.html
Author: 且行且码
Title: Elasticsearch 入门实战(4)–Java Low Level REST Client 使用