Composite Id

[umk8yw]

I would be glad to contribute at implementation of a solution for defining multiple fields as an identifier for a business model.

[bartoszwalacik]

Just to summarize, this issue is about making this mapping possible:

class Person {
    @Id String name
    @Id String surname
    @Id LocalDate dob
    ...
}

and id should be equiv to this mapping, which is currently supported

class Person {
   @Id PersonId personId
    ...
}

class PersonId {
 String name
 String surname
 LocalDate dob
}

[umk8yw]

I was thinking to change to EntityType with a Set<JaversProperty> instead of the JaversProperty idProperty field and adapt the rest of the functionality.

[bartoszwalacik]

bare Set is not ok in terms of OO modeling but we can create a dedicated class fot that, lets say EntityId and hide this set

[umk8yw]

ok, this was my approach into EntityDefinitionBuilder, I've created a dedicated class UniqueKey to store Set<String> propertyNames and I've created method:

public EntityDefinitionBuilder withCompositeId(String... compositeIdPropertyNames) {
    	Validate.argumentsAreNotNull(compositeIdPropertyNames);
    	this.uniqueKey = Optional.of(new UniqueKey(compositeIdPropertyNames));
    	return this;
    }

so when Javers is built to have the possibility to add multiple fields as id

[bartoszwalacik]

OK, now when you have access to javers repo, could you come up with a failing E2E test and push it to a new branch? This test should be a specification for our new Composite Id feature.

[umk8yw]

when I tried to run again the my test, I found another problem at some code added on 8 December:

 private String localIdAsString(Object localId) {
        PrimitiveOrValueType idPropertyType = getIdProperty().getType();
        return idPropertyType.smartToString(localId);
    }

because my id is a ComplexEntity this method fails.
I've done a pull request so you can see exactly what I am talking about, its title is Composite Id #625 - found problem with new method "localIdAsString"

[bartoszwalacik]

so, javers clashes because you have forced JaversType of your Id Property to EntityType:

.registerEntity(entityDefinition(ComplexEntity.class).withIdPropertyName("code").build())
registerEntity(entityDefinition(TenderLocation.class).withIdPropertyName("complexEntity").build()

It's not possible for now, JaversType of an Id Property can be only Primitive or Value.

[bartoszwalacik]

btw, i'm not sure why this kind of example,
I thought that we want to achieve sth like this:

class Person {
    @Id String name
    @Id String surname
    @Id LocalDate dob
    ...
}

[umk8yw]

yes, I want to be able to define multiple fields as an id, but I want to be able to do this at javers build, and some of the fields defined as id will not be Primitive or Value.

in the pull request is exactly the example of the way I've imagined it.

Javers javers = JaversBuilder.javers().registerEntity(EntityDefinitionBuilder.entityDefinition(ComplexEntity.class)
                                                .withIdPropertyName("code").build())
				.registerEntity(EntityDefinitionBuilder.entityDefinition(TenderLocation.class)
						.withCompositeId("location", "complexEntity").build())
				.registerEntity(EntityDefinitionBuilder.entityDefinition(TenderAirline.class)
						.withCompositeId("code", "tenderLocation").build())
				.build();

[bartoszwalacik]

You are talking about 2 different issues, one issue is composite Id, so possibility to point more than one Id property for an Entity (with both ways, annotations and javersBuilder). That's what we agreed on.
Second issue is possibility to use Entity as Id property, and that's what I don't want in javers because it brakes the rule that Id property can be only Primitive or Value (see https://javers.org/documentation/domain-configuration/#entity-id). I don't want to change this rule, moreover, I think that this is not good idea in terms of domain model. Why to put one Entity as an Id of another Entity?

[umk8yw]

ok, then what solution do you see for this kind of situation?
I've chosen this approach because I have 3 entities which all have the equals method overriden and I have to specify their id because all of then have multiple fields defined as id.
more, there is a hierarchical relation between entities.

ComplexEntity
    |__ List<Location>
             |__ List<Airline>

and Location has in its unique key ComplexEntity and Airline also has in its unique key a Location.

my first try was to make all of them ValueObject but the result was not the one expected.

[bartoszwalacik]

@umk8yw i don't see Airline and Location classes, could you express your issue in more general way? What feature or features you want to add to JaVers finally? Would this features be useful for other Javers users?

[ismaelgcosta]

@bartoszwalacik I opened a solution for this issue. and its a simple change needed to make this case possible.

#644

In my case I have an entity which is the Id of another entity.

Like
Person
|___ PersonDocumentation
Where

Documentation
|___
@id Person

I can't change this structure because Person saves personDocumentation by cascade and the Id of my documentation is the Id of my People. And i can`t change this because I work in a legacy project.

Please help me with that.