On Tue, 8 Mar 2022 16:51:22 GMT, John R Rose <[email protected]> wrote:
>> src/java.base/share/classes/java/lang/runtime/Carrier.java line 48:
>>
>>> 46:
>>> 47: /**
>>> 48: * This class is used to create objects that have number and types of
>>
>> The class javadoc seems a bit on the thin side. I would say something on the
>> fact that the shape of the carrier is determined by a MethodType, etc, and
>> add an example to illustrate basic usage.
>
> Agreed. Also, this class is unusual in that it is not instantiated; like
> `Arrays` or `Collections` it is a (small) bundle of static factories (or are
> they algorithms?). I think as such it should be called `Carriers`.
>
> I'm slightly surprised the MH factories are not factored through a metaobject
> of the form
>
> record CarrierBinding(
> MethodType methodType,
> MethodHandle constructor,
> List<Class<?>> componentTypes,
> List<MethodHandle> components)
> { … }
>
>
> The presupposition here, I suppose, is that carriers will only be used by
> condy or similar quasi-statically configured clients, so having the multiple
> lookups through a hidden table is no burden, and the clients can always keep
> the associations correct (between constructors and various component
> accessors).
>
> **But** if I were to use carriers to manage intermediate structures in (say)
> a serialization package (for instance) I would need to make my own records
> like the above for my own bookkeeping, and I would be slightly miffed that
> the Carrier API insisted on doing a de-novo lookup twice on each MT key (to
> say nothing of me having to create the MT key first).
>
> **And** if I were to use carriers in that way (away from condy), **then** I
> would want to skip the step of building the MethodType, and wish for a
> factory method for CarrierBinding instances that took a plain List<Class>, as
> well as a factory method that took the MethodType (which is convenient for
> condy).
>
> BTW, it would be normal to give the name `Carrier` (which is a good name BTW)
> to the record type that embodies the group of method handles, so `record
> Carrier(…constructor…components…) {…factories…}`.
>
> I suppose stuff like this could be added later. But it's worth considering
> now, simply because there is an early decision point between a class named
> `Carrier` and a static-only class named `Carriers`.
Will do. When I wrote this code, I wasn't expecting the external exposure.
Hence...
-------------
PR: https://git.openjdk.java.net/jdk/pull/7744
