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本文基于Java Low Level REST Client 7.x版本，为您介绍Elasticsearch Java API的用法。

准备工作

• 安装Java，要求JDK版本为1.8及以上。

• 创建Baidu Elasticsearch实例，版本7.4.2。

  注意 Low Level Client能够与任何版本的Elasticsearch兼容，因此客户端版本可以为任何版本，本文以7.4.2版本为例。

• 创建Java Maven工程，并将如下的pom依赖添加到Java工程的pom.xml文件中。

pom依赖

<dependency> <groupId>org.elasticsearch.client</groupId> <artifactId>rest</artifactId> 

<version>7.4.2</version> </dependency> <dependency> <groupId>org.apache.httpcomponents

</groupId> <artifactId>httpasyncclient</artifactId> <version>4.1.4</version> </dependency> <dependency> 

<groupId>org.apache.httpcomponents</groupId> <artifactId>httpcore-nio</artifactId> <version>4.4.13</version>

 </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> 

<version>4.5.6</version> </dependency> <dependency> <groupId>org.apache.httpcomponents</groupId> 

<artifactId>httpcore</artifactId> <version>4.4.12</version> </dependency> <dependency> <groupId>commons-codec

</groupId> <artifactId>commons-codec</artifactId> <version>1.10</version> </dependency> <dependency> 

<groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> <version>1.2</version> </dependency>

示例

以下代码为使用Java Low Level REST ClientI对Elasticsearch进行了查询，可供参考。

import java.io.IOException; import org.apache.http.HttpEntity; 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.entity.ContentType; import org.apache.http.impl.

client.BasicCredentialsProvider; import org.apache.http.impl.nio.client.HttpAsyncClientBuilder; import 

org.apache.http.nio.entity.NStringEntity; import org.apache.http.util.EntityUtils; import org.elasticsea

rch.client.Request; import org.elasticsearch.client.Response; import org.elasticsearch.client.RestClient; 

import org.elasticsearch.client.RestClientBuilder; public class RestClientTest742 { public static void

 main(String[] args) { final CredentialsProvider credentialsProvider = new BasicCredentialsProvider(); 

//访问用户名和密码为您创建Elasticsearch实例时设置的用户名和密码。 credentialsProvider.setCredentials(AuthScope.

ANY, new UsernamePasswordCredentials("{访问用户名}", "{访问密码}")); // 通过builder创建rest client，配置http 

client的HttpClientConfigCallback。 // ES HTTP URL 在Baidu Elasticsearch界面中可以查询 RestClient restClient

 = RestClient.builder(new HttpHost("{ES HTTP URL}", 8200)) .setHttpClientConfigCallback(new RestClientBu

ilder.HttpClientConfigCallback() { @Override public HttpAsyncClientBuilder customizeHttpClient(HttpAsy

ncClientBuilder httpClientBuilder) { return httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider);

 } }).build(); try { // 创建request Request request = new Request( "POST", "/{index_name}/_search");

 // 配置请求体 request.setEntity(new NStringEntity("{\"query\":{\"match_all\":{}}}", ContentType.APPLICATION

_JSON)); Response response = restClient.performRequest(request); System.out.println(EntityUtils.toString(

response.getEntity())); } catch (IOException e) { e.printStackTrace(); } } }

以上示例代码中带{}的参数需要替换为您具体业务的参数，详情请参见代码注释。

更多Java Low Level REST Client的使用特性，请参见Java Low Level REST Client官方文档。