Re: [hibernate-dev] Making APIs more Lambda-friendly
Good idea.
So, ResultTranformer will extend both the ResultRowTransformer and
ResultListTransformer so
it will inherit both methods.
Actually, the `transformList(List list)` is only needed by
`DistinctResultTransformer`, so most of the time we'd only have to pass
`ResultRowTransformer`.
Vlad
On Tue, Mar 1, 2016 at 1:55 PM, Gunnar Morling <gunnar(a)hibernate.org> wrote:
Hi,
Tinkering with result transformers, I wished I'd be able to express a
tuple transformation like this, using Java 8 Lambda-style:
session.createQuery( "SELECT foo, bar FROM Baz" )
.transformResultTuples( (tuple, aliases) -> { return tuple[0]
+ " " + tuple[1]; } )
.list();
That requires an interface with a single abstract method ("functional
interface") describing the Lambda type. The current ResultTransformer
interface has two methods, so it cannot be used as is.
I thus propose to deprecate ResultTransformer and add two new,
separate contracts: ResultRowTransformer and ResultListTransformer.
Query#setResultTransformer() would be superseded by two new methods:
transformResultTuples() and transformResultList().
Note that this change is fully compatible with previous Java versions:
One still can pass an (anonymous) implementation of the contracts when
stuck to Java 6/7. That backwards-compatible design is a really nice
trait of how Lambdas have been added to the Java language.
Lambda-friendliness is something which I think we should generally
keep in mind when designing new APIs. Maybe there also other ones
existing, that'd benefit from retrofitting.
Any thoughts?
Thanks,
--Gunnar
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