使用最新的客户端RestHighLevelClient 7.12.1调用旧版本的ElasticSearch exp :6.8.8

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.12.1</version>
</dependency>

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;

public class ElasticsearchClient {
    private static final String HOST = "localhost";
    private static final int PORT = 9200;

    public static RestHighLevelClient createClient() {
        return new RestHighLevelClient(
                RestClient.builder(new HttpHost(HOST, PORT, "http")));
    }
}

import org.elasticsearch.action.get.GetRequest;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.common.xcontent.XContentType;

import java.io.IOException;

public class ElasticsearchExample {
    public static void main(String[] args) {
        RestHighLevelClient client = ElasticsearchClient.createClient();

        GetRequest getRequest = new GetRequest("your_index", "your_document_id");
        try {
            GetResponse getResponse = client.get(getRequest, RequestOptions.DEFAULT);
            String sourceAsString = getResponse.getSourceAsString();
            // 处理获取到的数据
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 关闭客户端连接
        try {
            client.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}