[infinispan-dev] Lambda Serialization

[William Burns]

Actually I have a PR that will go in before the 8.2 Final release that uses
this [1].  Specifically check out the ClusterExecutor interface.  It
doesn't have the issues of streams with overloading existing methods,
however it adds both overloaded variants and you can see how the tests
invoke those.

[1] https://github.com/infinispan/infinispan/pull/4008

On Wed, Feb 17, 2016 at 3:23 AM Galder Zamarreño <galder at redhat.com> wrote:

> Hey Will,
>
> A very interesting discovery!
>
> Do you have a branch were you've tried this out? I'd like to play with it
> to see it in action and analyse the downsides more closely.
>
> Cheers,
> --
> Galder Zamarreño
> Infinispan, Red Hat
>
> > On 9 Feb 2016, at 17:36, William Burns <mudokonman at gmail.com> wrote:
> >
> > I wanted to propose a pretty simple way of making the lambdas
> serializable by default that I stumbled upon while working on another issue.
> >
> > I noticed that in the method resolution of the compiler it does some
> nice things [1].  To be more specific when you have 2 methods with the same
> name but vary by argument types, it will attempt to pick the most
> "specific" one.  Specific in this case you can think of if I can cast one
> argument type to the other but it can't be cast to this type, then this one
> is most specific.
> >
> > Here is an example, given the following class
> >
> > interface SerializableFunction<T, R> extends Serializable, Function<T, R>
> >
> > The stream interface already defines:
> >
> >    Stream map(Function<? super T, ? extends R> mapper);
> >
> > But we could add this to the CacheStream interface
> >
> >   CacheStream map(SerializableFunction<? super T, ? extends R> mapper);
> >
> > In this case you have 2 different map methods accessible from your
> CacheStream instance.  When passing a lambda the Java compiler will
> automatically choose the most specific one (in this case the
> SerializableFunction one since Function can't be cast to
> SerializableFunction).  This will then make the lambda automatically
> Serializable.  In this way nothing special has to be done (ie. explicit
> cast) to make the instance Serializable.
> >
> > This allows anyone using our Cache interface to immediately get lambdas
> that are Serializable when using Streams.
> >
> > The main problem however would be ambiguity because the Serialization
> would only be applied assuming you are using a defined class of CacheStream
> etc.  Also this means there are 2 methods (but that seems fine to me), so
> it could cause a bit of confusion.  The non serialization method is still
> helpful if people want to their own Externalizer, since their
> implementation doesn't have to implement Serializable then.
> >
> > What do you guys think?  It seems like a decent compromise to me.
> >
> >  - Will
> >
> >
> >
> >
> >
> > [1]
> https://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.12.2.5
> >
> >
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>
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