The questions concerning the relationships are never made when I use de command:
yo jhipster:entity author
I'm using the option: _java8 + mongoDB_.
This is normal: if you use MongoDB you don't have relationships.
This only works with JPA + SQL
Well, I'm really not a expert on this, but according to mongodb reference, it can contain document references. Spring's driver's manual also claims to do all the mapping for you.  Even when we have embedded documents, isn't it the case where at least a private List<Entity> relatedEntities should be placed in the model class?
We only support relationships for SQL-based mappings.
For NoSQL, whatever the solution is (I am currently implementing Cassandra), this won't be done, as it doesn't work (OK, you can put everything in a MongoDB document or use a SuperColumn in Cassandra, but those only work for small collections, and are not scalable as you put everything in the same item, so the interest for those is quite low)
support for embedded documents and dbref in MonogDB projects would be very useful.
+1
For the current limited MongoDB domain object modeling support, you only can do some sort of hack for embedded documents so that you can get a better code structure to work on. . 
+1 for supporting embedded documents and dbref in MongoDB =)
+1 for supporting embedded documents and dbref in MongoDB =)
+1000 for supporting embedded documents and dbref in MongoDB =)
Actually, i'm implementing that manually, but it would be wonderfull if it was supported "natively"
Can you open up a new ticket for this? And contributions on MongoDB are really welcome!
My pleasure, i will shoot when i'll have some bandwith this week (short delays & close deadlines on a project)
+1
+1 for supporting embedded documents and dbref in MongoDB =)
There's no need saying "+1" on this old ticket: we all agree it would be a good feature (I even told it yesterday on the core dev mailing list, see https://groups.google.com/forum/?hl=en#!topic/jhipster-dev/KytDq6GGzyQ ). Nobody has ever coded this, and when there's no contribution, it just doesn't happen...
I'm sorry but I won't do it myself, as I don't have the need, and I'm not investing time in MongoDB.
So instead of saying "+1", please tell me you'd like to work on this, and the ticket is yours.
lol, actually, I have added the comment, then I noticed there is an open Feature request,
I'll see what I can do on that. 
Excellent ! +1 for the PR :-)
How can I contribute to this part? Because I have a project using SpringBoot, SpringSecurity, MongoDB, ZullProxy and a lot of other technologies that JHipster works too. But now, my database is full of DBRef relationships because I use Morphia as Mongo Framework and I'm very excited to migrate my project to JHipster and I would like to improve this functionality. Thanks
@daibertdiego here is our contributing guide - we all agree that would be a great feature, but we have never found anyone to do it...
Please note that we might refactor the MongoDB support soon, as with Spring Boot 2 we might introduce the MongoDB reactive support.
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Excellent ! +1 for the PR :-)