Spring Mongo DB @DBREF

My suggestion is not to set that Claim class into separate @Document or just switch back to Relational Databases, because it's not a Mongo approach. Also, if you insist on current architecture you can try using @DBRef above that List in User.class into smth like this:

public class ParentModel {

    @Id
    private String id;

    private String name;

    private ParentType parentType;

    private SubType subType;

    @DBRef
    private List<Model> models;

....
}

If you reference your Claims in the User class with @DBRef, your JSON should not only contain the ID but the reference to the collection where to find the ID as well, like this:

{
  "name" : "KSK", 
  "claim" : [ 
     { 
       "$ref" : "claim", // the target collection
       "$id" : ObjectId("52ffc4a5d85242602e000000")
     }
  ] 
}

That is how Spring-Data maps your Java objects to MongoDB. If you start with a blank database and let Spring create and save the relations, you should have no problems using

 @DBRef List<Claim> claims;