如何在低级Rest客户端API中编写Match_all搜索查询

import org.apache.http.HttpHost;
import org.elasticsearch.client.Request;
import org.elasticsearch.client.Response;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;

public class MatchAllSearchExample {
    public static void main(String[] args) throws IOException {
        RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
        RestClient restClient = builder.build();

        Request request = new Request("POST", "/your_index_name/_search");
        String requestBody = "{ \"query\": { \"match_all\": {} } }";
        request.setJsonEntity(requestBody);

        Response response = restClient.performRequest(request);
        String responseBody = EntityUtils.toString(response.getEntity());

        System.out.println(responseBody);

        restClient.close();
    }
}