如何在java中生成弹性搜索嵌套聚合？

TransportClient client = new PreBuiltTransportClient(Settings.EMPTY)
        .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("localhost"), 9300));

SearchRequest searchRequest = new SearchRequest("index_name");
SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();
sourceBuilder.query(QueryBuilders.matchAllQuery());
sourceBuilder.aggregation(AggregationBuilders.terms("agg_name").field("nested_field"));
searchRequest.source(sourceBuilder);

SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

SearchHits hits = searchResponse.getHits();
for (SearchHit hit : hits) {
    // 处理搜索结果
}

Aggregations aggregations = searchResponse.getAggregations();
Terms agg = aggregations.get("agg_name");
for (Terms.Bucket bucket : agg.getBuckets()) {
    // 处理聚合结果
}