java operation mongodb group by query aggregation query

  List<DBObject> jsonlist = new ArrayList<DBObject>();
        // 查询条件
        BasicDBObject matchFields = new BasicDBObject();
        matchFields.put("mvnoId", new BasicDBObject("$eq", arg1));
        matchFields.put("orgId", new BasicDBObject("$eq", arg2));
        matchFields.put("country", new BasicDBObject("$eq", country));

        // 分组
        BasicDBObject groupFields = new BasicDBObject();
        Map<String, String> properties = new HashMap<String, String>();
        properties.put("country", "$country");
        groupFields.put("_id", properties);
        groupFields.put("testType", new BasicDBObject("$max", "$testType"));
        groupFields.put("age", new BasicDBObject("$sum", "$age"));

        BasicDBObject group = new BasicDBObject();
        group.put("$group", groupFields);
        jsonlist.add(group);

        // 输出列
        BasicDBObject projectFields = new BasicDBObject();
        projectFields.put("country", "$_id.country");
        projectFields.put("testType", "$testType");
        projectFields.put("age", "$age");

        BasicDBObject project = new BasicDBObject();
        project.put("$project", projectFields);
        jsonlist.add(project);

        // 分页
        BasicDBObject skip = new BasicDBObject();
        skip.put("$skip", (data.getCurrentPage() - 1) * data.getPerPageCount());
        jsonlist.add(skip);
        BasicDBObject limit = new BasicDBObject();
        limit.put("$limit", data.getPerPageCount());
        jsonlist.add(limit);

        AggregationOutput outPut = mongoTemplate.getCollection(collectionName).aggregate(jsonlist);
        Iterable<DBObject> it =  outPut.results();