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本文基于Java High 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 High Level Client能够向上兼容，但为了保证最大程度地使用最新版客户端的特性，推荐High Level Client版本与集群版本一致。

• 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>elasticsearch-

rest-high-level-client</artifactId> <version>7.4.2</version> </dependency> <dependency> 

<groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-core</artifactId> <version>2.7</version>

 </dependency> <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-api</artifactId> 

<version>2.7</version> </dependency>

示例

以下代码为使用Create Index API创建索引，使用异步调用的方式写入文档，删除文档，使用Delete API删除该索引等操作的示例，可供参考。

import java.io.IOException; 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.HttpAsync

ClientBuilder; import org.elasticsearch.action.ActionListener; import org.elasticsearch.action.admin.

indices.delete.DeleteIndexRequest; 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.action.support.master.

AcknowledgedResponse; 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.CreateIndexRequest; import org.elasticsearch.

client.indices.CreateIndexResponse; import org.elasticsearch.common.settings.Settings; import org.

elasticsearch.common.xcontent.XContentBuilder; import org.elasticsearch.common.xcontent.XContentFactory; 

import org.elasticsearch.common.xcontent.XContentType; 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 RestClientBuilder

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

RestClientBuilder.HttpClientConfigCallback() { @Override public HttpAsyncClientBuilder customizeHttpC

lient(HttpAsyncClientBuilder httpClientBuilder) { return httpClientBuilder.setDefaultCredentialsProvider

(credentialsProvider); } }); // RestHighLevelClient实例通过REST low-level client builder进行构造。 

RestHighLevelClient client = new RestHighLevelClient(builder); try { //创建索引 CreateIndexRequest 

createRequest = new CreateIndexRequest("my_index"); //创建的每个索引都可以有与之关联的特定设置。

 createRequest.settings(Settings.builder() .put("index.number_of_shards", 3) .put("index.number_of_replicas", 1)

 .put("index. refresh_interval", "10s") ); // 创建索引时创建文档类型映射 createRequest.mapping("{\n" + " 

 \"message\": {\n" + "      \"properties\": {\n" + "        \"message\": {\n" + " 

 \"type\": \"text\"\n" + "        }\n" + "      }\n" + "    }\n" + "  }", XContentType.JSON); 

// 同步执行创建索引操作 CreateIndexResponse createIndexResponse = client.indices().create(createRequest, 

RequestOptions.DEFAULT); System.out.println("create index successfully! response : "

 + createIndexResponse.toString()); // 写入文档 // 以XContentBuilder对象的形式提供，Elasticsearch 

内部会帮我们生成JSON内容 XContentBuilder jsonBuilder = XContentFactory.jsonBuilder(); jsonBuilder.startObject();

 { jsonBuilder.field("user", "Kobe Bryant"); jsonBuilder.field("number", 24); jsonBuilder.field("message", 

"One of the greatest basketball players since the 21st century"); } jsonBuilder.endObject(); IndexRequest

 indexRequest = new IndexRequest("my_index").id("1").source(jsonBuilder); //异步执行写入文档操作，

方法不会阻塞并立即返回。 ActionListener<IndexResponse> listener = new ActionListener<IndexResponse>()

 { @Override public void onResponse(IndexResponse indexResponse) { //执行成功时调用。 Response以参数方式提供

 System.out.println("Index doc successfully! response : " + indexResponse.toString()); } @Override public

 void onFailure(Exception e) { //在失败的情况下调用。 引发的异常以参数方式提供 System.out.println("Index doc

 fail!"); e.printStackTrace(); } }; //异步执行索引请求需要将IndexRequest实例和ActionListener实例传递给异步方法：

 client.indexAsync(indexRequest, RequestOptions.DEFAULT, listener); // 删除文档 DeleteRequest deleteRequest 

= new DeleteRequest("my_index").id("1"); // 执行删除文档操作 DeleteResponse deleteResponse = client.delete

(deleteRequest, RequestOptions.DEFAULT); System.out.println("Delete doc successfully! \n" + deleteResponse.

toString() + "\n" + deleteResponse.status()); // 指定要删除的索引名称 DeleteIndexRequest deleteIndexRequest 

= new DeleteIndexRequest("my_index"); // 执行删除索引操作 AcknowledgedResponse deleteIndexResponse = 

client.indices().delete(deleteIndexRequest, RequestOptions.DEFAULT); System.out.println("delete index 

successfully! response : " + deleteIndexResponse.toString()); } catch (IOException ioException) 

{ // 异常处理。 ioException.printStackTrace(); } finally { // 在不需要使用client后，将client关闭。

 try { client.close(); } 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 High Level REST Client的使用特性，请参见Java High Level REST Client官方文档。