There are also some improvements to make to the ServiceLoader API spec,
and at that time we'll lock in alignment of API spec and JLS.
(Consistent terminology; duplication of rules only where essential;
appropriate "call outs" to module system concepts such as service binding).
Alex
On 3/17/2016 11:19 AM, Jonathan Gibbons wrote:
Konstantin,
The compiler checks that the service implementation implements the
service type.
I have confidence that when the final specification is published, there
will be suitable assertions (either explicit or implicit) to back up
that check.
-- Jon
On 03/17/2016 06:02 AM, Konstantin Barzilovich wrote:
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.buck...@oracle.com
<mailto:alex.buck...@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
