介绍

Java High Level REST Client (7.x) 是一个与 Elasticsearch 集群交互的强大工具，使服务器通信更加容易访问和高效。在本指南中，我们将引导您完成在阿里云 Elasticsearch 集群上使用高级 REST 客户端调用 Elasticsearch Java API 的步骤。

准备工作

第1步：创建Elasticsearch集群

确保您的集群版本与您计划使用的 Java High Level REST Client 版本相同或更高。有关分步说明，请参阅创建阿里云 Elasticsearch 集群。

第 2 步：启用自动索引

在 YAML 配置文件中启用自动索引功能。具体请参见配置YML文件。

步骤3：配置IP地址白名单

通过配置IP地址白名单确保正常通信。如果您通过 Internet 访问集群，请按照配置公共或私有 IP 地址白名单中的指南允许来自所需 IP 地址的请求。

第四步：安装JDK

安装 Java 开发工具包 (JDK) 1.8 或更高版本。有关详细信息，请参阅安装 JDK。

第5步：创建Java Maven项目

将必要的依赖项添加到您的 pom.xml 文件中。将依赖项中的版本号从 7.x 更改为您正在使用的高级 REST 客户端的特定版本。

    org.elasticsearch.client
    elasticsearch-rest-high-level-client
    7.x


    org.apache.logging.log4j
    log4j-core
    2.20.0


    org.apache.logging.log4j
    log4j-api
    2.20.0

示例：管理索引

下面是使用高级 REST 客户端创建和删除索引的示例。将占位符 {} 替换为您的具体参数。

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.elasticsearch.action.delete.DeleteRequest;
import org.elasticsearch.action.delete.DeleteResponse;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexResponse;
import org.elasticsearch.client.*;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class RestClientExample {
    private static final RequestOptions COMMON_OPTIONS;

    static {
        RequestOptions.Builder builder = RequestOptions.DEFAULT.toBuilder();
        builder.setHttpAsyncResponseConsumerFactory(
                new HttpAsyncResponseConsumerFactory
                        .HeapBufferedResponseConsumerFactory(30 * 1024 * 1024));
        COMMON_OPTIONS = builder.build();
    }

    public static void main(String[] args) {
        final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, 
            new UsernamePasswordCredentials("{Username}", "{Password}"));

        RestClientBuilder builder = RestClient.builder(new HttpHost("{Endpoint of the Elasticsearch cluster}", 9200, "http"))
                .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
                    @Override
                    public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
                        return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
                    }
                });

        RestHighLevelClient highClient = new RestHighLevelClient(builder);

        try {
            Map jsonMap = new HashMap();
            jsonMap.put("{field_01}", "{value_01}");
            jsonMap.put("{field_02}", "{value_02}");

            IndexRequest indexRequest = new IndexRequest("{index_name}", "_doc", "{doc_id}").source(jsonMap);
            IndexResponse indexResponse = highClient.index(indexRequest, COMMON_OPTIONS);
            long version = indexResponse.getVersion();
            System.out.println("Index document successfully! "   version);

            DeleteRequest deleteRequest = new DeleteRequest("{index_name}", "_doc", "{doc_id}");
            DeleteResponse deleteResponse = highClient.delete(deleteRequest, COMMON_OPTIONS);
            System.out.println("Delete document successfully! \n"   deleteResponse.toString());

            highClient.close();
        } catch (IOException ioException) {
            ioException.printStackTrace();
        }
    }
}

高并发配置

针对高并发场景，增加客户端连接数：

httpClientBuilder.setMaxConnTotal(500);
httpClientBuilder.setMaxConnPerRoute(300);

示例代码片段：

String host = "127.0.0.1";
int port = 9200;
String username = "elastic";
String password = "passwd";
final int max_conn_total = 500;
final int max_conn_per_route = 300;

RestHighLevelClient restHighLevelClient = new RestHighLevelClient(
  RestClient.builder(new HttpHost(host, port, "http")).setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
    public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
      httpClientBuilder.setMaxConnTotal(max_conn_total);
      httpClientBuilder.setMaxConnPerRoute(max_conn_per_route);
      return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
    }
  })
);

有关功能和配置的更多详细信息，请参阅官方 Java High Level REST Client 文档。

结论

使用 Java High Level REST Client 可确保与阿里云 Elasticsearch 集群高效交互。按照本指南充分利用您的 Elasticsearch 设置。
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