Raymond,
OK, so this is arguing that <interface.java/>
in an SCA <component/> should not be allowed to have a @remotable
attribute setting that is different
from that in the <componentType/> of the implementation used by the
component.
So one use case that was argued is the
one where the Java interface and the Java service implementation is fixed
and unchangable - and that neither says
@Remotable, although it is known that the interface & implementation
are
indeed remotable, In this case,
I don't see that anyone can use either of the techniques in your first
bullet.
Introspection will show the implementation
as using the unannotated interface and that will be interpreted as "local".
Creating a subinterface will not help
since introspection will only see the original implementation and its reference
to the original interface. If
we follow you approach below, then nothing can be done for such pre-existing
implementations
- they are always interpreted as local
and nothing can be done about them.
Or rather - I feel a Mediation coming
on... ;-)
We may argue that it is presumptious
to take an existing implementation class and assume we can treat it as
@Remotable
even though it was not created with
that in mind. However, I think that this flies in the face of reality.
Yours, Mike.
Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
Email:
From:
Raymond Feng/Burlingame/IBM@IBMUS
To:
Mike Edwards <>
Cc:
"OASIS Java" <>
Date:
24/02/2010 18:44
Subject:
Re: [sca-j] Re: [sca-assembly] Re: [sca-j]
ASSEMBLY-218: Review Interface Compatibility logic to accomodate @Remotable
attribute in the SCDL - proposal
Sorry for the confusion but I meant
to be the other way around:
* For implementation.java, we can annotate
the interface @Remotable or create a subinterface of an existing one and
add @Remotable. The componentType introspection will set the "remotable"
flag.
* For other implementation types such
as "implementation.osgi", we don't have the luxury to annotate
the interfaces. But when we map them into an SCA componentType, we know
that an interface from "service.exported.interfaces"
property is meant to be remotable. So the introspection of implementation.osgi
componentType can set the "remotable" flag.
What I'm trying to say is that we should
always control the "remotable" from the componentType and the
component configuration should just adapt to it.
Thanks,
Raymond
Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400,
Foster City, CA 94404, USA
E-mail: ,
Notes: Raymond Feng/Burlingame/IBM, Tel: 650-645-8117,
T/L: 367-8117
Personal Web Site: www.enjoyjava.com
Apache Tuscany: http://tuscany.apache.org
Co-author of Tuscany In Action: http://www.manning.com/laws
From:
Mike Edwards <>
To:
"OASIS Java" <>
Date:
02/23/2010 11:43 PM
Subject:
Re: [sca-j] Re: [sca-assembly] Re: [sca-j]
ASSEMBLY-218: Review Interface Compatibility logic to accomodate @Remotable
attribute in the SCDL - proposal
Raymond,
You seem to be implying that for some Java implementation types, that it
is possible to set the content of the componentType
so that some <interface.java/> element, @remotable="true"
would be set where the referenced Java interface class does not
have the @Remotable annotation.
In general, componentType is introspected from the Java artifacts - componentType
side files are used only where no other
mechanism is available (eg in C++ where introspection is only possible
on the original source code).
So, how can the componentType of these implementation types be manipulated
to apply the @remotable attribute?
Yours, Mike.
Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014 Mobile: +44-7802-467431
Email:
From:
Raymond Feng <>
To:
David Booz <>
Cc:
,
Date:
24/02/2010 01:14
Subject:
[sca-j] Re: [sca-assembly] Re: [sca-j]
ASSEMBLY-218: Review Interface Compatibility logic to accomodate @Remotable
attribute in the SCDL - proposal
IIRC, the use case is not to take a "local" java interface as-is
for SCA Java components. Instead, it was proposed to cover other POJO-style
implementation types such as OSGi where a set of interfaces are listed
in the "service.exported.interfaces"
property for remote services. In such cases, we derive an SCA componentType
from the OSGi properties and the "remotable" flag can be set
in the componentType service/reference interfaces.
To use a "local" java interface for SCA components, we can create
a subinterface and annotate it with @Remotable. It should be acceptable
because we are building an SCA java component (not wrapping other technology
that doesn't have the notion of Remotable).
What I'm arguing here is that allowing the component configuration (SCDL
interface.java/@remotable) to override the remotability of the componentType
service/reference doesn't seem to be a good practice. IMO, it should be
set in the componentType and the component should adapt to it.
Thanks,
Raymond
Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400, Foster City, CA 94404,
USA
E-mail: ,
Notes: Raymond Feng/Burlingame/IBM, Tel: 650-645-8117,
T/L: 367-8117
Personal Web Site: www.enjoyjava.com
Apache Tuscany: http://tuscany.apache.org
Co-author of Tuscany In Action: http://www.manning.com/laws
From:
David Booz/Poughkeepsie/IBM@IBMUS
To:
,
Date:
02/16/2010 11:48 AM
Subject:
Re: [sca-assembly] Re: [sca-j] ASSEMBLY-218:
Review Interface Compatibility logic to accomodate @Remotable attribute
in the SCDL - proposal
Thanks for cleaning up for the issue references.
I don't quite agree with your use cases. IIRC, the reason @remotable
was
added was to allow for the case where a Java interface, which cannot be
modified, is used as a remotable interface. Since there's no opportunity
to add the @Remotable annotation, an alternative mechanism was added.
However, since the SCA java component implementation spec decided not to
support the use of a componentType side file, there is no place other than
a component definition which can contain the remotable assertion. We
did
discuss the subclassing option was way to add remotability to an otherwise
unmodifiable interface class. It was tossed out as too cumbersome.
The cases you cited below are different because they run into the by-value,
by-reference issues that you outlined. I don't think we should be
in the
business of overriding local interfaces and allowing them to be turned
into
remote interfaces (and vice versa which can be even more dangerous). The
problem is that in the absence of an @Local annotation, SCA doesn't know
if
the interface is truly local or remote.
WRT your C1 and C2 example, it certainly doesn't seem like a smart thing
to
do, but I don't see any reason to stop it.
In 1) you suggest removing @remotable from component interfaces. If
we
did, that would disallow the use case for which we added the support in
the
first place.
...still, it's ugly...
Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:
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| Date: |
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|[sca-assembly] Re: [sca-j] ASSEMBLY-218: Review Interface Compatibility
logic to accomodate @Remotable attribute in the SCDL - proposal
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Hi,
The links to issues are incorrect. They should be:
http://www.osoa.org/jira/browse/JAVA-125
http://www.osoa.org/jira/browse/JAVA-153
IMO, the @remotable attribute in SCDL is tricky because it is the first
case that component configuration starts to alter the interface
remotability in the componentType. There are basically two use cases:
* A java component implements a "local" java interface and we
want to
expose such service to a remote binding.
* A java component with a reference of a "local" java interface
and we want
to use it to access a remote service.
Did we consider the case that more than one component uses the same Java
implementation class, for example:
Component C1 exposing S1 as web service.
<component name="C1">
<implementation.java class="test.TestServiceImpl"/>
<service name="S1">
<interface.java interface="test.TestService"
remotable="true"/> <!-- test.TestService interface doesn't
have @Remotable -->
<binding.ws .../>
</service>
</component>
Component C2 exposing S1 as a local service for binding.sca.
<component name="C2">
<implementation.java class="test.TestServiceImpl"/>
<service name="S1">
<interface.java interface="test.TestService"/>
</service>
</component>
Is this allowed? If so, do we expect test.TestServiceImpl to support both
the local pass-by-reference or remote pass-by-value semantics depending
on
the components that use the impl class?
A few crazy thoughts:
1) Based on the original use case, should we only allow the SCA
componentType to set the interface.java to be remotable instead of the
component, for example:
<componentType ...>
<service name="S1">
<interface.java interface="test.TestService"
remotable="true"/>
</service>
</componentType>
(Please note that componentType can be just an in-memory model. The XML
is
for illustration purpose.)
In fact, when we (Tuscany) implement OSGi remote services using SCA, we
generate the componentType from the OSGi properties
(service.exported.interfaces) so that the java interface is remotable.
2) For the direct use of "local" java interfaces as remotable
in Java
components, can we just have a subinterface so that:
@Remotable
public interface RemotableJavaInterface extends LocalJavaInterface {
}
Thanks,
Raymond
Raymond Feng
Senior Software Engineer, Apache Tuscany PMC Member & Committer
IBM Bay Area Lab, 1001 E Hillsdale Blvd, Suite 400, Foster City, CA 94404,
USA
E-mail: , Notes: Raymond Feng/Burlingame/IBM, Tel:
650-645-8117, T/L: 367-8117
Personal Web Site: www.enjoyjava.com
Apache Tuscany: http://tuscany.apache.org
Co-author of Tuscany In Action: http://www.manning.com/laws
From: David Booz/Poughkeepsie/IBM@IBMUS
To:
Cc:
Date: 02/16/2010 09:38 AM
Subje [sca-j] ASSEMBLY-218: Review Interface Compatibility logic to
ct: accomodate @Remotable attribute in the SCDL - proposal
Following discussion of Assembly-218 [1] on the Assembly TC telecon today,
I took a closer look at the Assembly, Java CAA and Java POJO specs. I've
copied the Java TC on this email for awareness.
The assembly spec rule for matching interfaces based on remotability is
fundamentally important, so I don't think we can change that. The
Java CAA
spec is the one that defines @remotable for <interface.java/>. The
Java
POJO spec contains the componentType introspection rules and describes
the
use of Java POJOs for component implementations.
IMHO, if there is any spec text in error or at the very least that we
should consider updating, it is the Java POJO spec [2]. Issue Java-125
[3]
and Java-153 [4] introduced the @remotable attribute but did not address
the trip hazard that is described in Assembly-218.
In the Java POJO spec [2], see section 2.2 (toward the end) and section
2.3. At both points the spec makes some very specific statements
about
interface remotability but leaves out any mention that the determination
of
remotability could be further altered by the introduction of @remotable
on
a component definition. Interestingly, section 2.2 was heavily updated
when Java issues 125 and 153 were resolved. Those were the Java issues
that introduced @remotable on <interface.java/> in the first place.
The
Java POJO spec is (in general) maniacally focused on the componentType
of a
Java component (I'm sure that's what was in all of the Java TC minds when
it resolved 125 and 153). This trip hazard [1] comes along with the
combination of a component definition which seems to have the ability to
assert remotability into an underlying componentType and an introspected
componentType which says local.
Let's see if others buy this analysis before I suggest moving the issue
to
the Java TC.
[1] http://www.osoa.org/jira/browse/ASSEMBLY-218
[2]
http://www.oasis-open.org/committees/download.php/36414/sca-javaci-1.1-spec-cd02.doc
[3] http://www.osoa.org/jira/browse/ASSEMBLY-125
[4] http://www.osoa.org/jira/browse/ASSEMBLY-153
Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093 or 8-295-6093
e-mail:
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