[hibernate-dev] Making APIs more Lambda-friendly

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 Query#setResultTransformer() would be superseded by two new methods: transformResultTuples() and transformResultList().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