Re: [HACKERS] JPA + enum == Exception

Tom,

How would setString know that the enum is actually an enum ? setString only
takes a string ?

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca


On Fri, Feb 8, 2013 at 12:45 AM, Tom Dunstan <tom@tomd.cc> wrote:

> Hi Tom!
>
> On 8 February 2013 15:25, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> > AFAIK this is just business as usual with JDBC: setString() implies that
> > the parameter is of a string type.  It'll fall over if the type actually
> > required is anything but a string.  (I'm no Java expert, but I seem to
> > recall that using setObject instead is the standard workaround.)
> >
> > Enums are not suffering any special hardship here, and I'd be against
> > weakening the type system to give them a special pass.
>
> Yes, you can use setObject(1, "enumval", Types.OTHER). I was hoping
> that setString might work, as mapping java enum values to strings in
> the database is a very common ORM technique that is built into
> basically all major ORMs including all that support the JPA standard,
> and it leads to people using varchars instead of typesafe enums in
> their dbs. If setString worked, people could migrate their schemas to
> the typesafe versions without touching any code. Using setObject
> people need to write a custom converter in most of those systems, and
> configure its use for each enum that they have. This then also makes
> swapping database backends difficult (for people who care about that
> sort of thing), since the jdbc calls are now different for postgresql
> vs anything else.
>
> Anyway, if there's no nice way to do it in the backend without adding
> implicit casts, and you're not happy with the costs of that as a
> solution, I guess that's that. I guess I was hoping that a text value
> parameter to a prepared statement could be treated as input when the
> type didn't match, but I don't know if that's feasible, and I guess
> it's probably opening the door to confusing error messages when
> someone provides the wrong type accidentally.
>
> Thanks
>
> Tom
>
>
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