How to do embedded documents using spring java mongo repository dynamically

I have one document from sample_collection1 as


{
	"_id": {
		"$oid": "5e597a2be08a070bab329ef3"
	},
	"field1": "field1",
	"field2": [{
		"field3": "1234123",
		"field4": [{
			"field5": "3432",
			"field6": ["5e5ac0008def101ffa037100"
			]
		}]
	}]
}

and other document from sample_collection2 in one of the following type as

{"_id":{"$oid":"5e5ac0008def101ffa037100”},”childfield1”:”5e5ac0008def101ffa037906","childfield2”:”childfield2”,"childfield3”:”childfield3”}

or as

{"_id":{"$oid":"5e5ac0008def101ffa037906”},”childfield1”:” 5e5ac0008def101ffa037100","childfield2”:”childfield2”,"childfield3”:”childfield3”}

how to get following response dynamically if there n number of such fields to refer from other collections using spring mongo repository

{
	"_id": {
		"$oid": "5e597a2be08a070bab329ef3"
	},
	"field1": "field1",
	"field2": [{
		"field3": "1234123",
		"field4": [{
			"field5": "3432",
			"field6": [{”childfield1”:” ","childfield2”:”childfield2”,"childfield3”:”childfield3”}
			]
		}]
	}]
}