ElasticsearchBES

    Low Level REST Client

    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.elasticsearch.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 RestClientBuilder.HttpClientConfigCallback() {
                        @Override
                        public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder 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

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