Check out example codes for "spring boot mongodb update subdocument". It will help you in understanding the concepts better.

Code Example 1

final Query query = new Query(new Criteria().andOperator(
        Criteria.where("_id").is("id"),
        Criteria.where("listA").elemMatch(Criteria.where("_id").is("id"))
));
final Update update = new Update().addToSet("listA.$.listB", stuff).set("listA.$.thing", "thing");
final WriteResult wr = mongoOperations.updateFirst(query, update, "collectionName");

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