"Provides" and "with" type relationships

[Konstantin Barzilovich]

Thanks.
It is described in API spec in detail.
But from compiler point of view, it is allowed to use implementation  
without inheritance.
It would be grate to add some of these statements to compiler spec, if it  
is possible.

Thanks,
Konstantin.

> Yes. 'uses' and 'provides' are nothing more than static declarations  
> that configure java.util.ServiceLoader, so all questions can be resolved  
> by looking at the ServiceLoader spec:  
> http://download.java.net/java/jigsaw/docs/api/java/util/ServiceLoader.html
>
> Alex
>
> On 3/16/2016 10:24 AM, Konstantin Barzilovich wrote:
>> Sorry, if this question was asked before.
>> Does service implementation need to inherit service interface?
>>
>> Thanks,
>> Konstantin.
>>
>>> // Ignore last mail (mail client did a surprising thing)
>>>
>>> A 'provides' clause specifies two things: a service interface and a
>>> service implementation. Using those terms helps to avoid confusion.
>>>
>>> A service interface does not have to be an interface; it can be an
>>> abstract class or even (not recommended) a concrete class.
>>>
>>> A service implementation must not be an interface, or an abstract
>>> class; it must be a concrete class.
>>>
>>> Therefore, it's legal (but not recommended) for a concrete class to be
>>> specified as both service interface and service implementation. It's
>>> illegal for an interface (or abstract class) to be specified as both
>>> service interface and service implementation. JCK will be writing
>>> tests for edge cases like this.
>>>
>>> Alex
>>>
>>> On 3/15/2016 12:39 PM, Paul Benedict wrote:
>>>> Thanks for your response Alex. If I am understanding you correctly,
>>>> "provides" is "not constrained to be an interface" because it can be  
>>>> "a
>>>> single interface or abstract class". So shouldn't my concrete class  
>>>> for
>>>> "provides" be rejected by the compiler? And is it okay that both types
>>>> were identical?
>>>>
>>>> Cheers,
>>>> Paul
>>>>
>>>> On Tue, Mar 15, 2016 at 2:26 PM, Alex Buckley <alex.buckley at oracle.com
>>>> <mailto:alex.buckley at oracle.com>> wrote:
>>>>
>>>>     The first operand to 'provides' (the "service interface") is not
>>>>     constrained to be an interface by "Modules in the Java Language  
>>>> and
>>>>     JVM". This is because the spec of j.u.ServiceLoader ("a service is
>>>>     represented by a single type, that is, a single interface or
>>>>     abstract class").
>>>>
>>>>     The second operand to 'provides' (the "service implementation") is
>>>>     constrained not to be an interface or an abstract class by  
>>>> "Modules
>>>>     in the Java Language and JVM". This is also because of the spec of
>>>>     j.u.ServiceLoader ("provider classes must have a zero-argument
>>>>     constructor so that they can be instantiated during loading").
>>>>
>>>>     Bear in mind that the JCK team can easily set up abstract test  
>>>> cases
>>>>     like this. What they can't do is check whether YOUR application  
>>>> runs
>>>>     on JDK-9-with-Jigsaw, or whether arbitrary JARs on YOUR classpath
>>>>     work as automatic modules.
>>>>
>>>>     Alex
>>>>
>>>>
>>>>     On 3/15/2016 12:07 PM, Paul Benedict wrote:
>>>>
>>>>         module z {
>>>>               exports z;
>>>>               provides z.Main with z.Main;
>>>>         }
>>>>
>>>>         The SOTM says "Service-provider declarations can be further
>>>>         interpreted to
>>>>         ensure that providers (e.g., com.mysql.jdbc.Driver) actually  
>>>> do
>>>>         implement
>>>>         their declared service interfaces" (section 4, para. 8).
>>>>
>>>>         I see javac checking that they are related types, but javac is
>>>>         not checking
>>>>         that "provides" is an interface type. That is what I was
>>>>         expecting based on
>>>>         the reading material.
>>>>
>>>>         The other unexpected outcome was that provides/with allows the
>>>>         identical
>>>>         type. I don't know if that's intended, but please advise.
>>>>
>>>>         PS: I did go through the open tickets this time (thanks Alan)
>>>>         and do not
>>>>         see any similar reports. If I missed it, I apologize; just
>>>>         trying not to
>>>>         waste your time by reporting a duplicate.
>>>>
>>>>         Cheers,
>>>>         Paul
>>>>
>>>>
>>
>>


-- 
Thanks,
Konstantin.