With this query, why did you return the data db.user.find (“_ id”: 101, “subhobbys.id”: 4}) of the embedded document?

This is the returned data structure:
{

"_id" : NumberLong(101),
 "_class" : "com.xxoo.smart.domain.entity.User",
 "age" : "31",
 "friendNum" : 0,
 "friendMessSwitch" : 1,
 "teamMessSwitch" : 1,
 "headUrl" : "http://7xll7k.com2.z0.glb.qiniucdn.com/jpg/1507a114a95icon_101_2015-10-18.jpg",
 "career" : "",
 "mobile" : "15801607348",
 "nickname": "Lai Le",
 "birthday" : "2015-1-1",
 "horoscope": "Gemini",
 "loginTime" : ISODate("2015-10-18T15:11:37.764Z"),
 "sexCn": "Male",
 "createTime" : ISODate("2015-10-18T02:30:44.869Z"),
 "signKey" : "3843",
 "signKeyTime" : ISODate("2015-10-18T02:30:44.869Z"),
 "position" : {
 "x" : 116.6661600000000050,
 "y" : 40.3549369999999996
 },
 "easemobUserName" : "15801607348",
 "easemobPassword" : "123456",
 "cid" : "4eda857959a6ac32e69635575bf40244",
 "teamNum" : 4,
 "clientOs" : "ANDROID",
 "clientOsVersion" : "1.0",
 "channel" : "SportO2O",
 "subHobbys" : [
 {
 "_id" : NumberLong(4),
 "bigHobbyId" : 1,
 "subHobbyName": "Badminton",
 "subHobbyId" : NumberLong(4),
 "levelType": "intermediate",
 "level" : "3",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/yumaoqiu.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 1
 },
 {
 "_id" : NumberLong(5),
 "bigHobbyId" : 1,
 "subHobbyName": "Ping Pong",
 "subHobbyId" : NumberLong(5),
 "levelType": "advanced",
 "level" : "5",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/pingpangqiu.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 1
 },
 {
 "_id" : NumberLong(16),
 "bigHobbyId" : 1,
 "subHobbyName": "Ice Hockey",
 "subHobbyId" : NumberLong(16),
 "levelType": "primary",
 "level" : "2",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/bingqiu.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 2
 },
 {
 "_id" : NumberLong(47),
 "bigHobbyId" : 4,
 "subHobbyName": "Bicycle",
 "subHobbyId" : NumberLong(47),
 "levelType": "intermediate",
 "level" : "3",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/zixingche.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 1
 },
 {
 "_id" : NumberLong(74),
 "bigHobbyId" : 6,
 "subHobbyName": "Sports Aircraft",
 "subHobbyId" : NumberLong(74),
 "levelType": "primary",
 "level" : "1",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/yundongfeiji.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 1
 },
 {
 "_id" : NumberLong(73),
 "bigHobbyId" : 6,
 "subHobbyName": "Motor Boat",
 "subHobbyId" : NumberLong(73),
 "levelType": "primary",
 "level" : "2",
 "sign" :  "http://7xll7k.com2.z0.glb.qiniucdn.com/mototing.png" ,
 "certFront" : "null",
 "certBack" : "null",
 "certStatus" : 0,
 "hobbyType" : 1
 }
 ],
 "equipments" : [],
 "comments" : [],
 "friendIds" : [
 NumberLong(102)
 ],
 "provinceName": "Beijing",
 "cityName": "beijing city",
 "areaName": "Haidian District, Beijing",
 "provinceId" : NumberLong(3318),
 "cityId" : NumberLong(1),
 "areaId" : NumberLong(7),
 "teams" : [],
 "teamIds" : [
 NumberLong(120),
 NumberLong(119),
 NumberLong(117)
 ],
 "fullName": "Haidian district, Beijing"

}