java 操作mongodb 聚合函数

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最近项目用mongdb，作为数据库。要实现抽奖项目，按照收集卡片的多少来排名，显示前15名的用户中奖信息。

cllection 名称： wzl_app_winnerlist 每次收集一张卡片都会有一条记录。

使用自带的命令行客户端聚合语句：

db.getCollection('wzl_app_winnerlist').aggregate([
{$match:{'times':'1'}},
{$group:{'_id'
:{'times':'$times','user_id':'$user_id','user_account':'$user_account'},'count':{$sum:1}}},
{$sort:{'count':-1}},
{$limit:15},
{$project:{'_id':0,'times':'$_id.times','user_id':'$_id.user_id','user_account':'$_id.user_account','count':1}}
]);

其中times,为活动期次，user_id ,为用户id,user_accout,为用户名, count 为统计数量。

$match:过滤条件

$group:分组按照_id 分组,并查询出数据。

$sort: 排序,按照count 降序排列。

$limit: 限制数量

$project: 聚合，0 不显示，1显示。

最后结果

[
{
"count": 31,
"times": "1",
"user_id": "20",
"user_account": "17812345678"
},
{
"count": 29,
"times": "1",
"user_id": "7",
"user_account": "18123456789"
},
{
"count": 23,
"times": "1",
"user_id": "1",
"user_account": "13524354057"
},
{
"count": 22,
"times": "1",
"user_id": "4",
"user_account": "13412345678"
},
{
"count": 20,
"times": "1",
"user_id": "11",
"user_account": "22222222222"
},
{
"count": 20,
"times": "1",
"user_id": "5",
"user_account": "15026994613"
},
{
"count": 17,
"times": "1",
"user_id": "16",
"user_account": "19193840921"
},
{
"count": 16,
"times": "1",
"user_id": "2",
"user_account": "13333333333"
},
{
"count": 16,
"times": "1",
"user_id": "10",
"user_account": "18412345678"
},
{
"count": 16,
"times": "1",
"user_id": "9",
"user_account": "18312345678"
},
{
"count": 15,
"times": "1",
"user_id": "13",
"user_account": "18012345678"
},
{
"count": 14,
"times": "1",
"user_id": "12",
"user_account": "33333333333"
},
{
"count": 14,
"times": "1",
"user_id": "19",
"user_account": "12345678909"
},
{
"count": 13,
"times": "1",
"user_id": "14",
"user_account": "18123456783"
},
{
"count": 13,
"times": "1",
"user_id": "17",
"user_account": "13234242343"
}
]

java driver 驱动聚合函数操作：

实现以上效果：

  public static String queryWinners(HttpServletRequest request,HttpServletResponse response,JsonNode node,String sUserID) throws Exception {  String times  = Util.getValue(node, "times") ;  String limitStr =  Util.getValue(node, "limit") ;  int limit = -1 ;  if (limitStr!=null&&!"".equals(limitStr)) {  limit  = Integer.parseInt(limitStr) ;  }else {limit = 10 ;  }    if (times==null||"".equals(times)) { return "{s:1,m:请求参数错误}";  }  //根据期次和用户id 查询  用户id 分组,limit 15 .  DBCollection collection = DBUtil.getCollection(Constant.WZL_APP_WINNERLIST);  DBObject matchBasicDBObjet = new BasicDBObject("$match",new BasicDBObject("times",times));  /* Group操作*/  DBObject groupFields = new BasicDBObject("_id", new BasicDBObject("times", "$times").append("user_id", "$user_id").append("user_account", "$user_account"));  groupFields.put("count", new BasicDBObject("$sum", 1));  DBObject group = new BasicDBObject("$group", groupFields);    // 排序操作  DBObject sortchBasicDBObjet = new BasicDBObject("$sort", new BasicDBObject("count",-1));  DBObject limitBasicDBObjet = new BasicDBObject("$limit",limit);  // project 操作  DBObject projectBasicDBObjet = new BasicDBObject("$project",  new BasicDBObject("_id",0).append("times", "$_id.times")  .append("user_id", "$_id.user_id").append("user_account", "$_id.user_account").append("count", 1));  List<DBObject> list = new ArrayList<DBObject>();  list.add(matchBasicDBObjet);  list.add(group);  list.add(sortchBasicDBObjet);  list.add(limitBasicDBObjet);  list.add(projectBasicDBObjet);    AggregationOutput output = collection.aggregate(list);CommandResult result = output.getCommandResult();//方案二// JsonNode resultnode = JsonUtil.getJson(result.getString("result"));//  logger.info(JsonMapper.toJsonString(resultnode));   logger.info(result.getString("result"));  return result.getString("result");}

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