Unidirectional OneToOne relationship is not working

[aelfricraven]

Hi,
I'm new to JHipster, but have seen a few examples already and it always seemd pretty straightforward.
Now that I'm giving it a try, I am already stumbling early on, with the JDL.
The documentation (https://www.jhipster.tech/jdl/relationships#examples) says I can create an unidirectional relationship by using this form:
relationship OneToOne {
Company{location} to Location
Branch{location} to Location
}
The generated code for location contains references to both Company and Branch, however. Am I missing something? My alternative woold be making the Location embeddable, but this is not possible, yet, if I understand it right.
Do you have any suggestions?
Thank!
ciao Thomas

[Tcharl]

Hi,

The thing that you put into bracket is the name of the relationship. I guess that the framework miss a fatal exception here.
if you want to make it work:

relationship OneToOne {
    Company{location} to Location{company}
    Branch{location} to Location{branch}
}

Plus posting a bug on this issues tracker please ;-)

[aelfricraven]

Hi,
Hi,
just to make sure there's no misunderstanding: I don't want to have the Location class to have a reference to either the Company or the Branch. All I want is a unidirectional relationship. To achieve this (according to the documentation) you should leave the {} away in the Location end.
Your suggesstion would create a bidirectional relationship and ends up with both an branch and a company attribute inside of the location, which is not needed in my case (and clutters the code).
Thanks!
ciao Thomas

[mshima]

Use ManyToOne instead of OneToOne.

OneToOne is bidirectional in JHipster because once the generator finds the OneToOne type on the left side, it creates the back reference.
Constraints will be created in the back reference to make it a OneToOne relationship, otherwise it’s effectively a ManyToOne relationship.

[mshima]

@OmarHawk supporting unidirectional OneToOne in JHipster can be tricky due to UI.
An alternative that may be easier to implement is:

relationship ManyToOne {
  @LiquibaseUnique Parent{child} to Child
}

[OmarHawk]

Ok, does not work for me, as I had previously something like this:

relationship OneToOne {
  Parent{child} to @Id @OnDelete("CASCADE") @OnUpdate("CASCADE") Child
}

which I converted to

relationship ManyToOne {
  @LiquibaseUnique Parent{child} to @Id @OnDelete("CASCADE") @OnUpdate("CASCADE") Child
}

as I wanted to avoid that extra column in the Child entity.

And that one does not work properly - the generated schema is dysfunctional as the generated liquibase relationship expects an additional column in the Child - which it does not have as it has the @Id annotation.

[OmarHawk]

What worked for me to make the specific relationship kind of unidirectional without producing inconsistencies was to just filter out the generated relationship through a local side-by-side blueprint like this:

get [BaseApplicationGenerator.POST_PREPARING_EACH_ENTITY]() {
    return this.asPostPreparingEachEntityTaskGroup({
      async postPreparingEachEntityTemplateTask({entity}) {
          entity.relationships = entity.relationships.filter(r => r.relationshipType !== 'one-to-one' || r.relationshipSide !== 'right');
      },
    });
  }

This way, the templates won't pick up this side of the relationship, making it effectively unidirectional in the way, I need it.
Don't know, if that's actually a good idea, but at least it works.

[mshima]

@OmarHawk I think we can remove the condition if it working and add backward compatibility.
Can you provide a PR?

[OmarHawk]

@OmarHawk I think we can remove the condition if it working and add backward compatibility. Can you provide a PR?

Sure about the PR. Maybe, it would be good to have this behaviour configurable through some sort of annotation to not break / change existing generated applications, implicitly having backwards compatibility.

Something like

relationship OneToOne {
  @Unidirectional Parent{child} to @Id @OnDelete("CASCADE") @OnUpdate("CASCADE") Child
}