Elasticsearch 6.4:传递给request.mapping()时XContentBuilder无法关闭

import org.elasticsearch.common.xcontent.XContentBuilder;
import org.elasticsearch.common.xcontent.XContentFactory;
import org.elasticsearch.action.admin.indices.create.CreateIndexRequest;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestHighLevelClient;

public class ElasticsearchExample {
    public static void main(String[] args) {
        try (RestHighLevelClient client = new RestHighLevelClient()) {
            XContentBuilder mappingBuilder = XContentFactory.jsonBuilder();
            mappingBuilder.startObject();
            // 构建mapping
            // ...
            mappingBuilder.endObject();

            CreateIndexRequest request = new CreateIndexRequest("index_name");
            request.mapping(mappingBuilder);

            // 执行请求
            // ...

            // 关闭XContentBuilder
            mappingBuilder.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}