Dynamic document loading with #DocumentRererence for Spring Data MongoDB - spring-boot

Question

Is there a way to stop loading the referenced document marked with #DocumentReference during an api call as it'd make the db calls heavy in case there are multiple referenced documents? Or is there better way to do that? I have tried #DBRef but that won't solve the problem as the existing database looks something like this:
{
"_id" : "833f7d",
"name" : "Del Rey Books",
"arconym" : "DRB",
"foundationYear" : 1977,
"books" : [
NumberLong(300000),
NumberLong(395652)
]
}
and #DBRef would make the db entry to look something like this if I save new data (therefore won't solve the problem) :
{
"_id" : "833f7d",
"name" : "Del Rey Books",
"arconym" : "DRB",
"foundationYear" : 1977,
"books" : [
{
"$ref" : "book",
"$id" : 300000
},
{
"$ref" : "book",
"$id" : 395652
}
]
}
The domain class looks something like this:
class Publisher {
// ...
#DocumentReference(lazy = true)
List<Book> books;
}
The GET api request fetches the whole referenced document in response body, but along with it also adds the keys (i) target - containing the same referenced document all over again. (ii) source - containing the id of the referenced object again. Something like this:
{
"_id" : "833f7d",
"name" : "Del Rey Books",
"arconym" : "DRB",
"foundationYear" : 1977,
"books" : [
{
"id" : 300000,
"isbn13" : "978-0345503800",
"title" : "The Warded Man",
"pages" : 432,
"target": {
id" : 300000,
"isbn13" : "978-0345503800",
"title" : "The Warded Man",
"pages" : 432,
},
"source" : 300000
},
{
"id" : 395652,
"isbn13" : "978-0345503800",
"title" : "The Sailor",
"pages" : 420,
"target": {
id" : 395652,
"isbn13" : "908-093830380",
"title" : "The Sailor",
"pages" : 420,
},
"source" : 395652
}
]
}
What is the significance of target, source all over again in the response body?
Also is there any other way to have references but not load the references in the response body during an API call? I was expecting (lazy = true) would do so, but it doesn't.