在java中使用MongoTemplate聚合操作MongoDB

参考链接：(  https://blog.csdn.net/baidu_38990811/article/details/80095495  )

    

　　Aggregation agg = Aggregation.newAggregation(    
            Aggregation.match(criteria),//条件  
            Aggregation.group("a","b","c","d","e").count().as("f"),//分组字段    
            Aggregation.sort(sort),//排序  
            Aggregation.skip(page.getFirstResult()),//过滤  
            Aggregation.limit(pageSize)//页数  
         );    
    AggregationResults<Test> outputType=mongoTemplate.aggregate(agg,"test",Test.class);    
    List<Test> list=outputType.getMappedResults(); 

或者处理结果：

AggregationResults<Document> result = mongoTemplate.aggregate(agg,tableName, Document.class);
result.getMappedResults().forEach(document ->{
　　Map<String, Object> map = new HashMap<String, Object>();
   for (String key : document.keySet()) {
   　　if ("_id".equals(key)) {
      　　map.put("_id", document.get("_id").toString());
       }else {
          map.put(key, document.get(key));
       }
   }
   resultList.add(map);
});