Method references in annotations?

Brian Goetz brian.goetz at
Sun Aug 14 14:52:13 PDT 2011

Method references which are convertible to functional (SAM) interfaces 
are in scope, and have in fact been part of the plan all along.  Method 
references may be converted to SAM types just like a lambda, with the 
same rules.

Converting method references to other things (e.g., 
java.lang.reflect.Method) for purposes of enabling convenience in 
annotation-based frameworks is quite a different thing.  Neal's 
characterization of "tangential" (and criticism of the term "omission") 
is accurate.

As to the mailing list, we are (still!) working on overcoming internal 
procedural roadblocks that will let us move the mailing list to 
somewhere more public.  The archives will be published when we are able 

On 8/14/2011 5:06 PM, Ben Evans wrote:
> I don't see why method references are "only tangentially related" to the
> scope of Project Lambda.
> Methods which expect a lambda must be able to accept either an anonymous
> function or a named method.
> Surely, no-one is suggesting otherwise?
> Given that, the mechanism for named methods we have is presumably to pass a
> MethodHandle which contains a reference to the named method. This is
> incredibly cumbersome and exactly the kind of overly verbose, boilerplate-y
> code that we should be able to do better than.
> I'm really failing to see why method references are not a consideration
> here.
> Also - can we please have a link to public archives for the EG?
> Thanks,
> Ben
> On Sat, Aug 13, 2011 at 11:59 AM, Neal Gafter<neal at>  wrote:
>> It's is a bit of a stretch to call it an "omission" that project lambda
>> hasn't specified language constructs only tangentially related to it's
>> scope.
>> On Saturday, August 13, 2011, Ben Evans<benjamin.john.evans at>
>> wrote:
>>> On Thu, Aug 11, 2011 at 12:14 AM, Stephen Colebourne
>>> <scolebourne at>wrote:
>>>> On 10 August 2011 20:24, Dan Smith<daniel.smith at>  wrote:
>>>>> Discussions along the lines of "yeah, those are things we should get
>> to
>>>> sometime" have happened here, internally at Oracle, and in the JSR 335
>>>> expert group.
>>>> I will just note that I've raised this before. Frameworks in
>>>> particular constantly have to wrestle with how to handle the lack of
>>>> method references, generally using strings. Adding method references
>>>> to the main body of code helps those framework writers a bit, but not
>>>> being usable in annotations is a major limitation and a huge missed
>>>> opportunity.
>>> Nor is this situation static.
>>> E.g. both JSR 349 (Bean Validation) and JSR 350 (effectively, Container
>>> Managed State) have glaringly obvious places where a method reference in
>> an
>>> annotation would be very useful.
>>> Have the reasons for this omission been discussed in detail on the JSR
>> 335
>>> EG? Is there a public Observers alias for that EG?
>>> Thanks,
>>> Ben

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