CODEWITHSUNDEEP
mongodbmongodb-queryspring-data-mongodb
iswok
iswok

Reputation: 39

Is it possible to retrieve the specific value in an array of objects inside an object in mongodb

Is it possible to retrieve the specific value in an array of objects inside an another object in mongodb??

@Document
class vehicleStation {
   @Id
   String stationId;
   List<car> cars;
}
@Document
class car{
   @Id
   String carNo;
   String name;
}

And my json structure will look like below

{"_id":"0001","cars":[{"_id":"C001", "name":"Honda"},{"_id":"C002","name":"Ford"}]}

Is it possible retrieve the value of "name" for a particular vehicleStation (stationId="0001" and carNo="C002") which is "Ford"

how to query the mongodb to get the value "Ford" for vehicleStation (stationId="0001" and carNo="C002")

Upvotes: 2

Views: 128

Answers (2)

Sridhar Nanjundeswaran
Sridhar Nanjundeswaran

Reputation: 754

Since you are doing an _id query at the top level this returns only one document. You can do

db.so.findOne({_id:"0001"},{cars:{$elemMatch:{"_id":"C002"}}}).cars[0]

to get the inner object or

db.so.findOne({_id:"0001"},{cars:{$elemMatch:{"_id":"C002"}}}).cars[0].name

to get only the name Note - If you have multiple subobjects with the _id as C002 this will only the first match as documented.

Upvotes: 2

Sridhar Nanjundeswaran
Sridhar Nanjundeswaran

Reputation: 754

You could do that using the $elemMatch projection operator. e.g. from the shell

> db.so.find({_id:"0001"},{cars:{$elemMatch:{"_id":"C002"}}})
{ "_id" : "0001", "cars" : [  {  "_id" : "C002",  "name" : "Ford" } ] }

Upvotes: 2

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