ElasticSearch 的 聚合（Aggregations）-javaAPI示例

好的，以下是一个简单的ElasticSearch聚合的Java API示例：

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.Client;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.aggregations.AggregationBuilders;
import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramInterval;
import org.elasticsearch.search.aggregations.bucket.histogram.Histogram;
import org.elasticsearch.search.aggregations.bucket.terms.Terms;
import org.elasticsearch.search.aggregations.metrics.sum.Sum;
import org.elasticsearch.search.aggregations.metrics.valuecount.ValueCount;

import static org.elasticsearch.index.query.QueryBuilders.rangeQuery;

public class ElasticSearchAggregationExample {

    public static void main(String[] args) {

        // 创建ElasticSearch客户端
        Client client = // ...;

        // 构建查询条件
        QueryBuilder query = QueryBuilders.boolQuery()
                .must(rangeQuery("timestamp").gte("2022-01-01T00:00:00").lte("2022-01-31T23:59:59"));

        // 构建聚合条件
        AggregationBuilder aggregation = AggregationBuilders
                .dateHistogram("sales_over_time")
                .field("timestamp")
                .dateHistogramInterval(DateHistogramInterval.DAY)
                .subAggregation(
                        AggregationBuilders
                                .terms("product_types")
                                .field("product_type")
                                .subAggregation(
                                        AggregationBuilders.sum("total_sales").field("sales"),
                                        AggregationBuilders.count("transaction_count").field("transaction_id")
                                )
                );

        // 执行查询
        SearchResponse response = client.prepareSearch("my_index")
                .setQuery(query)
                .addAggregation(aggregation)
                .execute()
                .actionGet();

        // 解析聚合结果
        Histogram histogram = response.getAggregations().get("sales_over_time");
        for (Histogram.Bucket bucket : histogram.getBuckets()) {
            System.out.println("Date: " + bucket.getKeyAsString());
            Terms productTypes = bucket.getAggregations().get("product_types");
            for (Terms.Bucket productType : productTypes.getBuckets()) {
                System.out.println("Product Type: " + productType.getKeyAsString());
                Sum totalSales = productType.getAggregations().get("total_sales");
                System.out.println("Total Sales: " + totalSales.getValue());
                ValueCount transactionCount = productType.getAggregations().get("transaction_count");
                System.out.println("Transaction Count: " + transactionCount.getValue());
            }
        }

        // 关闭客户端
        client.close();
    }
}

这个示例通过ElasticSearch的Java API执行了一个聚合，其中包含了两层嵌套聚合，分别按照日期和产品类型对销售数据进行了汇总，输出了每个日期和产品类型的销售总额和交易次数。