Creating a custom enum mapper and using it

[Aye Thu]

Hi JDBI peeps,

I'm currently on jdbi 3.6.x. I've got enums that extend the following interface:

public interface HasId {

    public Integer id();

}

public enum AppState implements HasId {

    PENDING(1),

    SCHEDULED(2),

    COMPLETED(3),

    CANCELLED(4),

    RESCHEDULED(5);

    private final Integer id;

    AppState(Integer id) {

        this.id = id;

    }

    @Override

    public Integer id() {

        return id;

    }

}

This id is used to save and query enums to/from the DB (and not the ordinal value). I created a custom ColumnMapper and a custom ColumnMapperFactory to handle this but am now trying to figure out how to "register" this so that the BeanMapper will use these. How can I do this (or am I even on the right path)?

In the docs I saw EnumStrategy but it doesn't look to be extensible (or customizable) this made me more confused concerning the right direction to handle custom enums. 

Thanks!

[Steven Schlansker]

> On Feb 29, 2020, at 11:35 AM, Aye Thu <aye...@gmail.com> wrote:
>
>
> This id is used to save and query enums to/from the DB (and not the ordinal value). I created a custom ColumnMapper and a custom ColumnMapperFactory to handle this but am now trying to figure out how to "register" this so that the BeanMapper will use these. How can I do this (or am I even on the right path)?

It should be as simple as calling registerColumnMapper(new AppStateColumnMapperFactory()) on your Jdbi before opening a handle that uses it.

Keep in mind that with latest Jdbi there's a new argument preparation facility, if you write a custom ArgumentFactory as well please consider implementing ArgumentFactory.Preparable otherwise the "vanilla" enum binder might win over yours anyway.

>
> In the docs I saw EnumStrategy but it doesn't look to be extensible (or customizable) this made me more confused concerning the right direction to handle custom enums.

Right, these are just the built-in strategies. You're on the right track, writing a custom mapper for a custom type, rather than thinking of it as a special enum strategy. (An enum is just a special case of "custom type")

[Aye Thu]

Yup, I was able to get it to work with registerColumnMapper. Thanks for the reminder related to argument binding also; right now I'm explicitly handling the parameter binding myself (instead of using the enum directly). Last question: what are the scenarios for using QualifiedColumnMapperFactory vs the regular ColumnMapperFactory?

Here's a quick blurb for the custom MapperFactory in case someone runs into a similar scenario:

@Override
public Optional<ColumnMapper<?>> build(QualifiedType<?> givenType, ConfigRegistry config) {
    
    return Optional.of(givenType.getType())
                   .map(GenericTypes::getErasedType)
                   .filter(c -> Enum.class.isAssignableFrom(c) && HasId.class.isAssignableFrom(c))
                   .map(clazz -> CustomEnumMapper.byId(clazz.asSubclass(Enum.class)));
}

[Steven Schlansker]

Qualifiers are for allowing annotations to select between different behaviors for the same type.

For example, a normal String argument will bind directly as a SQL varchar,
but if you add the @Json qualifying annotation (after installing appropriate jackson / gson module)
instead it will bind as a JSON literal string in a json column.

The feature is relatively new and does not have too many uses yet built-in.

> --
> You received this message because you are subscribed to the Google Groups "jDBI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to jdbi+uns...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/jdbi/6ee771ef-e5bb-4915-8121-fc45319119fe%40googlegroups.com.