使用elastic的resthighlevel api类似于：

// Create the client
    RestHighLevelClient client = new RestHighLevelClient(
            RestClient.builder(new HttpHost("localhost", 9200, "http")));

    // Specify the aggregation request
    SearchRequest searchRequest = new SearchRequest("proktor-activities");
    SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
    searchSourceBuilder.aggregation(AggregationBuilders
        .avg("avg_attention")
        .field("activity.attentionLevel"));

    searchRequest.source(searchSourceBuilder);

    // Execute the aggreagation with Elasticsearch
    SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);

    // Read the aggregation result
    Aggregations aggregations = response.getAggregations();
    Avg averageAttention = aggregations.get("avg_attention");
    double result = averageAttention.getValue();

    client.close(); // get done with the client

这里有更多信息。