介紹

Java High Level REST Client (7.x) 是一個與 Elasticsearch 叢集互動的強大工具，使伺服器通訊更容易存取和高效。在本指南中，我們將引導您完成在阿里雲 Elasticsearch 叢集上使用進階 REST 用戶端呼叫 Elasticsearch Java API 的步驟。

準備工作

步驟1：建立Elasticsearch集群

確保您的叢集版本與您計劃使用的 Java High Level REST Client 版本相同或更高。有關逐步說明，請參閱建立阿里雲 Elasticsearch 叢集。

第 2 步：啟用自動索引

在 YAML 設定檔中啟用自動索引功能。詳情請參閱配置YML檔。

步驟3：設定IP位址白名單

透過設定IP位址白名單確保正常通訊。如果您透過 Internet 存取集群，請依照設定公用或私人 IP 位址白名單中的指南允許來自所需 IP 位址的請求。

第四步：安裝JDK

安裝 Java 開發工具包 (JDK) 1.8 或更高版本。有關詳細信息，請參閱安裝 JDK。

步驟5：建立Java Maven項目

將必要的依賴項新增至您的 pom.xml 檔案中。將相依性中的版本號碼從 7.x 變更為您正在使用的進階 REST 用戶端的特定版本。

    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

範例：管理索引

以下是使用進階 REST 用戶端建立和刪除索引的範例。將佔位符 {} 替換為您的特定參數。

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();
        }
    }
}

高並發配置

針對高並發場景，增加客戶端連線數：

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

範例程式碼片段：

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);
    }
  })
);

有關功能和配置的更多詳細信息，請參閱官方 Java High Level REST Client 文件。

結論

使用 Java High Level REST Client 可確保與阿里雲 Elasticsearch 叢集高效互動。按照本指南充分利用您的 Elasticsearch 設定。
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