JAVA Rest High Level Client如何取聚合后得数据

对于刚刚学习es的童鞋来说，很容易不清楚怎么获取客户端对es文档的聚合结果，下面就演示一下模仿DSL写聚合，然后获取到聚合的结果。

一， 对于下面这个简单的聚合，目的是对于文档全文匹配，聚合颜色字段。把满足匹配的文档放入自定义名称的colors桶中，参照《elasticsearch权威指南》的范围限定聚合

 {
     "size" : 0,
     "query" : {
         "match_all" : {}
     },
     "aggs" : {
         "colors" : {
             "terms" : {
               "field" : "color"
             }
         }
     }
 }

二， 对照着这个DSL写我们的java rest client api的调用方法，供业务层调用

     /**
      * ES中查询所有color
      *
      * @param indices
      * @return
      */
     public SearchResponse getAllColor(String... indices) {
         SearchRequest searchRequest = new SearchRequest(indices);
         SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder().size(0);
         searchSourceBuilder.query(QueryBuilders.matchAllQuery());
         TermsAggregationBuilder builder = AggregationBuilders.terms("colors").field("color");
         searchSourceBuilder.aggregation(builder);
         searchRequest.source(searchSourceBuilder);

         try {
             return client.getHighLevelClient().search(searchRequest);
         } catch (IOException e) {
             throw new BizException("聚合失败：{}", e.getCause());
         }
     }

三， 在我们的业务层调用上文中的getAllColor方法获取response，对response解析，获取聚合的结果

      * 颜色信息
      *
      * @return
      */
     public List<String> getAllColorInfo() {
         SearchResponse response = highRestHelper.getAllColor(getIndices());
         Aggregations aggregations = response.getAggregations();
         ParsedStringTerms colorTerms = aggregations.get("app_group");
         List<String> colors = new ArrayList<>();
         List<? extends Terms.Bucket> buckets = colorTerms.getBuckets();
         for (Terms.Bucket bucket : buckets) {
             String appName = bucket.getKey().toString();
             colors.add(appName);
         }
         return colors;
     } 

至此即可获取所有的聚合结果，只要能够参照DSL，转换成相应的api调用，那么解析过程完全可以复用。