Mongodb 如何将时间戳转换为年月日日期

        Integer userId=aaa;

        GroupOperation groupOperation = Aggregation.group( "day" ).sum( "money" ).as( "todayIncome" ).count().as( "todayPayCount" );

        Aggregation aggregation = Aggregation.newAggregation(

                Aggregation.match(Criteria.where( "userId" ).is(userId)),

                project( "userId" , "money" ).andExpression( "{$dateToString: {date: { $add: {'$createTime', [0]} }, format: '%Y%m%d'}}" , new Date( 28800000 )).as( "day" ),

                groupOperation,

                sort(Sort.Direction.ASC, "_id" )

        );

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.List;

import com.mongodb.BasicDBObject;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBCursor;

import com.mongodb.DBObject;

import com.mongodb.MongoClient;

import com.mongodb.ServerAddress;

/**

  * mongo 数据库直连测试

  * @author fuhao

  *

  */

public class MongDBTest {

     public static void main(String[] args) throws Exception {

         List<ServerAddress> list = new ArrayList<ServerAddress>();

//      连接数据库   ip 端口

         list.add( new ServerAddress( "10.39.XXX.XXX" , 27010 ));

         MongoClient mongoClient = new MongoClient(list);

         //数据库名称

         DB psdoc = mongoClient.getDB( "qa_db_center" );

         //表明

         DBCollection collection=psdoc.getCollection( "base_user_info" );

         BasicDBObject queryObject = null ;

         // 时间查询    数据库看到的时间不是真实时间  加8小时后才是正确的时间

         DBObject dbObject = new BasicDBObject();

         String startDate = "2018-03-29 15:59:06" ;

         String endDate = "2018-03-29 16:30:46" ;

         SimpleDateFormat sdf = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" );

         dbObject.put( "$gte" , sdf.parse(startDate));

         dbObject.put( "$lte" ,  sdf.parse(endDate));

         queryObject = new BasicDBObject();

         queryObject.put( "create_time" ,dbObject);

         DBCursor find = collection.find(queryObject);

         while (find.hasNext()) {

              DBObject next = find.next();

              Object real_name = next.get( "real_name" );

              Object mobile = next.get( "mobile" );

              Object create_time = next.get( "create_time" );

              String str = sdf.format(create_time);

              System.out.println(real_name + "=====" +mobile + "=====" +str);

         }

          System.out.println( "结束" );

     }

}

db.getCollection( 'base_user_info' ).find({ "create_time" :{ "$gte" :ISODate( "2018-03-29 07:59:06" ), "$lte" :ISODate( "2018-03-29 08:30:46" )}});