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From Gilles <gil...@harfang.homelinux.org>
Subject Re: [LANG] Java 9 problems because of dependencies to java.desktop
Date Fri, 20 Jul 2018 10:06:40 GMT
Hi.

On Fri, 20 Jul 2018 09:47:21 +0100, sebb wrote:
> On 20 July 2018 at 00:09, Bruno P. Kinoshita
> <brunodepaulak@yahoo.com.br.invalid> wrote:
>>>What is the replacement for Observer/Observable recommended by
>>>the JDK developers?
>> I believe they suggest to use the PropertyListener which we have 
>> right now, but are in the java.beans module I think.
>> Alternatively, they also suggest in the javadocs to look into the 
>> java.util.concurrent package if concurrency is important.
>>
>> From what I understand about the latter option, it would mean 
>> building your own event-bus or listeners.

I've read that Observer/Observable will not be removed from the
JDK (but won't be maintained).  So, if the shortcomings are OK
for the purpose at hand, the issue is only the deprecation warning.

Does someone readily knows how to go about implementing an equivalent
functionality with "java.util.concurrent" classes?

Regards,
Gilles

>> As for the java.beans, a possible solution to avoid deprecation 
>> right now would be include the java.beans property listeners code in 
>> [lang]. Maybe internal only.
>
> AFAIK we cannot copy any JVM code into our codebase, even if marked 
> internal.
> It would have to be a clean-room implementation.
>
>> Bruno
>>
>>       From: Gilles <gilles@harfang.homelinux.org>
>>  To: dev@commons.apache.org
>>  Sent: Friday, 20 July 2018 11:05 AM
>>  Subject: Re: [LANG] Java 9 problems because of dependencies to 
>> java.desktop
>>
>> Hello.
>>
>> On Mon, 16 Jul 2018 21:30:00 +0000 (UTC), Bruno P. Kinoshita wrote:
>>>>What about introducing our own state listener interface? The 
>>>> original
>>>>interface from the beans package was used just for convenience
>>>> because
>>>>it already existed. But it would of course be possible to have a
>>>> simple
>>>>functional interface to notify listeners about state changes.
>>> Hmmm, that's an option as well.
>>> Looks like they had the beans interface which we used, then later 
>>> we
>>> had the java.util.Observable for a while, and now they are 
>>> suggesting
>>> users to move to the beans interface, as one of the alternatives.
>>> As some Java 9 users possibly wouldn't want to import the 
>>> java.beans
>>> module, perhaps having this new interface could be an interesting
>>> alternative.
>>> I believe we would have to
>>> [ ] decide whether to introduce an interface similar to
>>> PropertyListener, or to Observable[ ] if the backward compatibility
>>> changed, we must deprecate the existing classes
>>> [ ] release a new version of lang with this new interface and the
>>> updated circuit breakers[ ] and either delete the deprecated 
>>> classes
>>> or leave it until for some more releases
>>> I wonder what others think about this option?
>>
>> What is the replacement for Observer/Observable recommended by
>> the JDK developers?
>>
>> Regards,
>> Gilles
>>
>>> Cheers
>>> Bruno
>>>
>>>
>>>      From: Oliver Heger <oliver.heger@oliver-heger.de>
>>>  To: dev@commons.apache.org
>>>  Sent: Tuesday, 17 July 2018 4:13 AM
>>>  Subject: Re: [LANG] Java 9 problems because of dependencies to
>>> java.desktop (Was: Re: [LANG] Thoughts about Lang 4.0)
>>>
>>>
>>>
>>> Am 16.07.2018 um 13:40 schrieb Bruno P. Kinoshita:
>>>> Saw some recent activity around lang 3.8, and remembered about 
>>>> this
>>>> issue, and then looked for this thread.
>>>>
>>>> Gilles' point is really good! Here's the Java 9 docs with the
>>>> deprecation warning, copied below as well
>>>> 
>>>> https://docs.oracle.com/javase/9/docs/api/index.html?java/util/Observable.html
>>>>
>>>>
>>>> "This class and the Observer interface have been deprecated. The
>>>> event model supported by Observer and Observable is quite limited, 
>>>> the
>>>> order of notifications delivered by Observable is unspecified, and
>>>> state changes are not in one-for-one correspondence with
>>>> notifications. For a richer event model, consider using the 
>>>> java.beans
>>>> package.  For reliable and ordered messaging among threads, 
>>>> consider
>>>> using one of the concurrent data structures in the
>>>> java.util.concurrent package. For reactive streams style 
>>>> programming,
>>>> see the Flow API."
>>>>
>>>>
>>>>
>>>> So I guess the best we can do right now is add the @deprecated
>>>> annotations, with an explanation in the javadocs. And also add a 
>>>> note
>>>> about it in the release notes.
>>>>
>>>> Does that sound like a good plan? Adding a link to this thread in
>>>> the pull request as well.
>>>>
>>>
>>> What about introducing our own state listener interface? The 
>>> original
>>> interface from the beans package was used just for convenience
>>> because
>>> it already existed. But it would of course be possible to have a
>>> simple
>>> functional interface to notify listeners about state changes.
>>>
>>> Oliver
>>>
>>>>
>>>> Cheers
>>>> Bruno
>>>>
>>>>
>>>>
>>>>
>>>> ________________________________
>>>> From: Stephen Colebourne <scolebourne@joda.org>
>>>> To: Commons Developers List <dev@commons.apache.org>
>>>> Sent: Monday, 11 June 2018 9:26 AM
>>>> Subject: Re: [LANG] Java 9 problems because of dependencies to
>>>> java.desktop (Was: Re: [LANG] Thoughts about Lang 4.0)
>>>>
>>>>
>>>>
>>>> Good spot. I think that means [lang] would have to have its own 
>>>> copy
>>>> of the JDK interfaces. or just deprecate the functionality without
>>>> replacement.
>>>> Stephen
>>>>
>>>> On 10 June 2018 at 22:11, Gilles <gilles@harfang.homelinux.org>
>>>> wrote:
>>>>> Hello.
>>>>>
>>>>> On Sun, 10 Jun 2018 21:34:49 +0200, Oliver Heger wrote:
>>>>>>
>>>>>> Hi Bruno,
>>>>>>
>>>>>> Am 10.06.2018 um 00:52 schrieb Bruno P. Kinoshita:
>>>>>>>
>>>>>>> Hi all,
>>>>>>>
>>>>>>> There is a patch [1] for LANG-1339 [2] that I would like to
>>>>>>> merge. The
>>>>>>> discussion around this issue can be found in the rest of this
>>>>>>> e-mail thread.
>>>>>>>
>>>>>>> The patch basically deprecates the existing classes that depend
>>>>>>> on
>>>>>>> java.desktop, and provide alternative implementations. The
>>>>>>> previous classes
>>>>>>> used java.desktop classes for the PropertyChangeListener. And

>>>>>>> the
>>>>>>> alternative ones instead use Java 7's java.util.Observer.
>>>>>
>>>>>
>>>>> Is it a good idea to use deprecated classes[1] in new code?
>>>>>
>>>>> Regards,
>>>>> Gilles
>>>>>
>>>>> [1]
>>>>> 
>>>>> https://docs.oracle.com/javase/9/docs/api/java/util/Observable.html
>>>>>
>>>>>
>>>>>>>
>>>>>>>
>>>>>>> This will make it easier to provide [lang] as java 9, without
>>>>>>> requiring
>>>>>>> users to include a dependency to java.desktop.
>>>>>>> Planning to merge it during the next week if there are no
>>>>>>> objections
>>>>>>> here.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Bruno
>>>>>>
>>>>>>
>>>>>> agreed. This seems to be the best what we can do.
>>>>>>
>>>>>> Oliver
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> [1] https://github.com/apache/commons-lang/pull/275
>>>>>>>
>>>>>>> [2] https://issues.apache.org/jira/browse/LANG-1339
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ________________________________From: Benedikt Ritter
>>>>>>> <britter@apache.org>
>>>>>>> To: Commons Developers List <dev@commons.apache.org>
>>>>>>> Sent: Monday, 5 June 2017 10:49 PM
>>>>>>> Subject: [LANG] Java 9 problems because of dependencies to
>>>>>>> java.desktop
>>>>>>> (Was: Re: [LANG] Thoughts about Lang 4.0)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Am 25.05.2017 um 18:23 schrieb Oliver Heger
>>>>>>>> <oliver.heger@oliver-heger.de>:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Am 24.05.2017 um 13:55 schrieb Stephen Colebourne:
>>>>>>>>>
>>>>>>>>> On 23 May 2017 at 17:17, sebb <sebbaz@gmail.com>
wrote:
>>>>>>>>>>>
>>>>>>>>>>> Yes, the
>>>>>>>>>>> code compiles and both can be on the classpath,
but it is a
>>>>>>>>>>> pain to
>>>>>>>>>>> use, just a different kind of hell.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> I don't see what the problem is here.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Library A that depends on lang3 returns a Pair.
>>>>>>>>> Library B that depends on lang4 takes a Pair.
>>>>>>>>> Application cannot pass Pair from A to the B without
>>>>>>>>> conversion.
>>>>>>>>>
>>>>>>>>> My point is that it is possible to over-worry about jar
hell.
>>>>>>>>> Joda-Time removed some methods when it went from v1.x
to 
>>>>>>>>> v2.x,
>>>>>>>>> but
>>>>>>>>> didn't change package name or maven co-ordinates. It
was far
>>>>>>>>> more
>>>>>>>>> important that end-users didn't have two different LocalDate
>>>>>>>>> classes
>>>>>>>>> (a problem that couldn't be avoided when moving to Java
8).
>>>>>>>>> I've never
>>>>>>>>> seen any feedback about the incompatibility causing jar
hell.
>>>>>>>>>
>>>>>>>>> The same is true here. It is vital to think properly
about
>>>>>>>>> which is
>>>>>>>>> the worse choice, not just assume that jar hell must
always 
>>>>>>>>> be
>>>>>>>>> avoided.
>>>>>>>>>
>>>>>>>>> I remain completely unconvinced that removing these two
>>>>>>>>> problematic
>>>>>>>>> methods justifies the lang4 package name, forcing end-users

>>>>>>>>> to
>>>>>>>>> have
>>>>>>>>> three copies of the library on the classpath. It should
need
>>>>>>>>> much,
>>>>>>>>> much more to justify lang4 package name. In fact I've
yet to
>>>>>>>>> hear
>>>>>>>>> anything else much in this thread that justifies a major
>>>>>>>>> release.
>>>>>>>>
>>>>>>>>
>>>>>>>> I also think that a new major release just to fix this problem
>>>>>>>> would be
>>>>>>>> overkill and cause clients even more trouble.
>>>>>>>>
>>>>>>>> Would the following approach work as a compromise:
>>>>>>>>
>>>>>>>> - [lang] declares an optional dependency to the desktop 
>>>>>>>> module.
>>>>>>>> - All affected classes (AbstractCircuitBreaker and its two
sub
>>>>>>>> classes)
>>>>>>>> are marked as deprecated.
>>>>>>>> - Copies are created from the original classes with slightly
>>>>>>>> changed
>>>>>>>> names or in a new package (tbd). These copies use a new change
>>>>>>>> listener
>>>>>>>> mechanism.
>>>>>>>>
>>>>>>>> IIUC, the resulting [lang] module can now be used without
the
>>>>>>>> dependency
>>>>>>>> to desktop when the new classes are used. The dependency
will
>>>>>>>> only be
>>>>>>>> needed for the deprecated versions.
>>>>>>>
>>>>>>>
>>>>>>> Let’s do it like this. Sounds like the right way to me.
>>>>>>>
>>>>>>> Benedikt
>>>>>>>
>>>>>>>>
>>>>>>>> Oliver
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Stephen
>>>>>>>>>


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