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Posted to user@flink.apache.org by Kristoffer Sjögren <st...@gmail.com> on 2015/08/18 11:01:06 UTC
Java 8 and type erasure
Hi
Potential fix for writing flink jobs using lamdas without Eclipse JDT?
https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
Cheers,
-Kristoffer
Re: Java 8 and type erasure
Posted by Timo Walther <tw...@apache.org>.
Hey Kristoffer,
sorry for the late reply. I was on vacation.
Here you can find my initial email that also contains a description and
a link to the patch:
http://mail.openjdk.java.net/pipermail/compiler-dev/2015-January/009220.html
The Eclipse JDT team didn't really need a patch. Their compiler does not
throw away generic type information in early stages so it was easy to
add them to the generic signature (which "accidentally" happened at the
beginning and now works again with help of a compiler option):
https://bugs.eclipse.org/bugs/show_bug.cgi?id=449063
The OpenJDK/Oracle JDK compiler mainly works without generic type
information (they call "erasure()" intentionally), so the produced class
files do not contain information that can be determined by any hacks.
It would be great if we could convince them. I think many projects need
more type-safety for lambda expressions.
On 18.08.2015 14:58, Stephan Ewen wrote:
> Timo should still have the patch!
>
> If you want to re-vive the thread, that'd be great. I'd be happy to
> support it.
>
>
>
> On Tue, Aug 18, 2015 at 2:51 PM, Kristoffer Sjögren <stoffe@gmail.com
> <ma...@gmail.com>> wrote:
>
> Do you have a link to these patches?
>
> Reading through the thread, I get the feeling they didn't reject the
> idea completely.
>
> Considering there are also other projects (Crunch, Spark, Storm, etc)
> that would benefit from this, maybe we can convince them together?
>
>
> On Tue, Aug 18, 2015 at 2:27 PM, Stephan Ewen <sewen@apache.org
> <ma...@apache.org>> wrote:
> > Yep, Timo wrote the patch, both for OpenJDK and JDT - the JDT
> one was
> > accepted in the end.
> >
> >
> > On Tue, Aug 18, 2015 at 2:09 PM, Robert Metzger
> <rmetzger@apache.org <ma...@apache.org>> wrote:
> >>
> >> Exactly, Timo opened the thread.
> >>
> >> On Tue, Aug 18, 2015 at 2:04 PM, Kristoffer Sjögren
> <stoffe@gmail.com <ma...@gmail.com>>
> >> wrote:
> >>>
> >>> Yeah, I think I found the thread already... by Timo Walther?
> >>>
> >>> On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen
> <sewen@apache.org <ma...@apache.org>> wrote:
> >>> > Would have been great. I had high hopes when I saw the trick
> with the
> >>> > "constant pool", but this is only to make what Flink does
> already
> >>> > applicable
> >>> > to non-serializable lambdas.
> >>> >
> >>> > If you want to help us with this, I'll ping you for some
> support on the
> >>> > OpenJDK mailing list ;-)
> >>> >
> >>> > On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren
> <stoffe@gmail.com <ma...@gmail.com>>
> >>> > wrote:
> >>> >>
> >>> >> I suspected that you already had looked into this, but it
> was worth a
> >>> >> try. It would make everything so much easier.
> >>> >>
> >>> >> Thanks for the explanation :-)
> >>> >>
> >>> >>
> >>> >> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen
> <sewen@apache.org <ma...@apache.org>>
> >>> >> wrote:
> >>> >> > Hi Kristoffer!
> >>> >> >
> >>> >> > I looked through the code as well. In fact, Flink
> currently uses the
> >>> >> > trick
> >>> >> > mentioned for Serializable Lambdas in the gist you sent me.
> >>> >> >
> >>> >> > This works well for lambdas that return simple types
> (primitives or
> >>> >> > classes
> >>> >> > without generics). The information for the generic
> parametrization
> >>> >> > is
> >>> >> > unfortunately really erased, it is in no signature or
> anything.
> >>> >> >
> >>> >> > Java has the concept of "generic method signatures",
> which means
> >>> >> > that a
> >>> >> > method gets a signature string that includes the generic
> types.
> >>> >> > These
> >>> >> > signatures are generated for regular functions, but
> OpenJDK and
> >>> >> > OracleJDK do
> >>> >> > not generate them for synthetic methods (like lambdas).
> >>> >> >
> >>> >> > We tried to submit a patch to OpenJDK to add these generic
> >>> >> > signatures to
> >>> >> > lambda methods, but they did not like the fact that we
> try to figure
> >>> >> > out
> >>> >> > the
> >>> >> > generic types of lambdas. I hope they change their minds
> at some
> >>> >> > point...
> >>> >> >
> >>> >> > Stephan
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek
> >>> >> > <aljoscha@apache.org <ma...@apache.org>>
> >>> >> > wrote:
> >>> >> >>
> >>> >> >> Unfortunately, this also doesn't work for the same
> reasons. The
> >>> >> >> generic
> >>> >> >> types of generic parameters of a lambda are not stored
> anywhere.
> >>> >> >> Stephan
> >>> >> >> mentioned to me that the only possibility right now
> would be to
> >>> >> >> look at
> >>> >> >> the
> >>> >> >> code using something like ASM to find a cast in the code
> to the
> >>> >> >> concrete
> >>> >> >> type of the generic parameter.
> >>> >> >>
> >>> >> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren
> <stoffe@gmail.com <ma...@gmail.com>>
> >>> >> >> wrote:
> >>> >> >>>
> >>> >> >>> How about https://github.com/jhalterman/typetools?
> >>> >> >>>
> >>> >> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
> >>> >> >>> <aljoscha@apache.org <ma...@apache.org>>
> >>> >> >>> wrote:
> >>> >> >>> > Hi Kristoffer,
> >>> >> >>> > I'm afraid not, but maybe Timo has some further
> information. In
> >>> >> >>> > this
> >>> >> >>> > extended example we can see the problem:
> >>> >> >>> >
> https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The
> >>> >> >>> > output
> >>> >> >>> > is:
> >>> >> >>> >
> >>> >> >>> > Type is: class
> >>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > class
> org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > Type is: class
> >>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > class
> org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > Type is :
> >>> >> >>> >
> >>> >> >>> >
> >>> >> >>> >
> >>> >> >>> >
> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> >>> >> >>> > class
> org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> >
> >>> >> >>> > So with the two lambda calls it does not correctly
> determine the
> >>> >> >>> > generic
> >>> >> >>> > parameter of Thing while it works with the anonymous
> class.
> >>> >> >>> >
> >>> >> >>> > I was exited when I saw the example because we've
> been trying
> >>> >> >>> > for so
> >>> >> >>> > long to
> >>> >> >>> > get this to work. Maybe we have to wait for java 19
> to get this
> >>> >> >>> > to
> >>> >> >>> > work. ;-)
> >>> >> >>> >
> >>> >> >>> > Thanks a lot for helping, though. :D
> >>> >> >>> > Aljoscha
> >>> >> >>> >
> >>> >> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren
> >>> >> >>> > <stoffe@gmail.com <ma...@gmail.com>>
> >>> >> >>> > wrote:
> >>> >> >>> >>
> >>> >> >>> >> Hi
> >>> >> >>> >>
> >>> >> >>> >> Potential fix for writing flink jobs using lamdas
> without
> >>> >> >>> >> Eclipse
> >>> >> >>> >> JDT?
> >>> >> >>> >>
> >>> >> >>> >>
> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
> >>> >> >>> >>
> >>> >> >>> >> Cheers,
> >>> >> >>> >> -Kristoffer
> >>> >> >
> >>> >> >
> >>> >
> >>> >
> >>
> >>
> >
>
>
Re: Java 8 and type erasure
Posted by Stephan Ewen <se...@apache.org>.
Timo should still have the patch!
If you want to re-vive the thread, that'd be great. I'd be happy to support
it.
On Tue, Aug 18, 2015 at 2:51 PM, Kristoffer Sjögren <st...@gmail.com>
wrote:
> Do you have a link to these patches?
>
> Reading through the thread, I get the feeling they didn't reject the
> idea completely.
>
> Considering there are also other projects (Crunch, Spark, Storm, etc)
> that would benefit from this, maybe we can convince them together?
>
>
> On Tue, Aug 18, 2015 at 2:27 PM, Stephan Ewen <se...@apache.org> wrote:
> > Yep, Timo wrote the patch, both for OpenJDK and JDT - the JDT one was
> > accepted in the end.
> >
> >
> > On Tue, Aug 18, 2015 at 2:09 PM, Robert Metzger <rm...@apache.org>
> wrote:
> >>
> >> Exactly, Timo opened the thread.
> >>
> >> On Tue, Aug 18, 2015 at 2:04 PM, Kristoffer Sjögren <st...@gmail.com>
> >> wrote:
> >>>
> >>> Yeah, I think I found the thread already... by Timo Walther?
> >>>
> >>> On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen <se...@apache.org>
> wrote:
> >>> > Would have been great. I had high hopes when I saw the trick with the
> >>> > "constant pool", but this is only to make what Flink does already
> >>> > applicable
> >>> > to non-serializable lambdas.
> >>> >
> >>> > If you want to help us with this, I'll ping you for some support on
> the
> >>> > OpenJDK mailing list ;-)
> >>> >
> >>> > On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <
> stoffe@gmail.com>
> >>> > wrote:
> >>> >>
> >>> >> I suspected that you already had looked into this, but it was worth
> a
> >>> >> try. It would make everything so much easier.
> >>> >>
> >>> >> Thanks for the explanation :-)
> >>> >>
> >>> >>
> >>> >> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org>
> >>> >> wrote:
> >>> >> > Hi Kristoffer!
> >>> >> >
> >>> >> > I looked through the code as well. In fact, Flink currently uses
> the
> >>> >> > trick
> >>> >> > mentioned for Serializable Lambdas in the gist you sent me.
> >>> >> >
> >>> >> > This works well for lambdas that return simple types (primitives
> or
> >>> >> > classes
> >>> >> > without generics). The information for the generic parametrization
> >>> >> > is
> >>> >> > unfortunately really erased, it is in no signature or anything.
> >>> >> >
> >>> >> > Java has the concept of "generic method signatures", which means
> >>> >> > that a
> >>> >> > method gets a signature string that includes the generic types.
> >>> >> > These
> >>> >> > signatures are generated for regular functions, but OpenJDK and
> >>> >> > OracleJDK do
> >>> >> > not generate them for synthetic methods (like lambdas).
> >>> >> >
> >>> >> > We tried to submit a patch to OpenJDK to add these generic
> >>> >> > signatures to
> >>> >> > lambda methods, but they did not like the fact that we try to
> figure
> >>> >> > out
> >>> >> > the
> >>> >> > generic types of lambdas. I hope they change their minds at some
> >>> >> > point...
> >>> >> >
> >>> >> > Stephan
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> >
> >>> >> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek
> >>> >> > <al...@apache.org>
> >>> >> > wrote:
> >>> >> >>
> >>> >> >> Unfortunately, this also doesn't work for the same reasons. The
> >>> >> >> generic
> >>> >> >> types of generic parameters of a lambda are not stored anywhere.
> >>> >> >> Stephan
> >>> >> >> mentioned to me that the only possibility right now would be to
> >>> >> >> look at
> >>> >> >> the
> >>> >> >> code using something like ASM to find a cast in the code to the
> >>> >> >> concrete
> >>> >> >> type of the generic parameter.
> >>> >> >>
> >>> >> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <
> stoffe@gmail.com>
> >>> >> >> wrote:
> >>> >> >>>
> >>> >> >>> How about https://github.com/jhalterman/typetools?
> >>> >> >>>
> >>> >> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
> >>> >> >>> <al...@apache.org>
> >>> >> >>> wrote:
> >>> >> >>> > Hi Kristoffer,
> >>> >> >>> > I'm afraid not, but maybe Timo has some further information.
> In
> >>> >> >>> > this
> >>> >> >>> > extended example we can see the problem:
> >>> >> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The
> >>> >> >>> > output
> >>> >> >>> > is:
> >>> >> >>> >
> >>> >> >>> > Type is: class
> >>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > Type is: class
> >>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> > Type is :
> >>> >> >>> >
> >>> >> >>> >
> >>> >> >>> >
> >>> >> >>> >
> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> >>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >> >>> >
> >>> >> >>> > So with the two lambda calls it does not correctly determine
> the
> >>> >> >>> > generic
> >>> >> >>> > parameter of Thing while it works with the anonymous class.
> >>> >> >>> >
> >>> >> >>> > I was exited when I saw the example because we've been trying
> >>> >> >>> > for so
> >>> >> >>> > long to
> >>> >> >>> > get this to work. Maybe we have to wait for java 19 to get
> this
> >>> >> >>> > to
> >>> >> >>> > work. ;-)
> >>> >> >>> >
> >>> >> >>> > Thanks a lot for helping, though. :D
> >>> >> >>> > Aljoscha
> >>> >> >>> >
> >>> >> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren
> >>> >> >>> > <st...@gmail.com>
> >>> >> >>> > wrote:
> >>> >> >>> >>
> >>> >> >>> >> Hi
> >>> >> >>> >>
> >>> >> >>> >> Potential fix for writing flink jobs using lamdas without
> >>> >> >>> >> Eclipse
> >>> >> >>> >> JDT?
> >>> >> >>> >>
> >>> >> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
> >>> >> >>> >>
> >>> >> >>> >> Cheers,
> >>> >> >>> >> -Kristoffer
> >>> >> >
> >>> >> >
> >>> >
> >>> >
> >>
> >>
> >
>
Re: Java 8 and type erasure
Posted by Kristoffer Sjögren <st...@gmail.com>.
Do you have a link to these patches?
Reading through the thread, I get the feeling they didn't reject the
idea completely.
Considering there are also other projects (Crunch, Spark, Storm, etc)
that would benefit from this, maybe we can convince them together?
On Tue, Aug 18, 2015 at 2:27 PM, Stephan Ewen <se...@apache.org> wrote:
> Yep, Timo wrote the patch, both for OpenJDK and JDT - the JDT one was
> accepted in the end.
>
>
> On Tue, Aug 18, 2015 at 2:09 PM, Robert Metzger <rm...@apache.org> wrote:
>>
>> Exactly, Timo opened the thread.
>>
>> On Tue, Aug 18, 2015 at 2:04 PM, Kristoffer Sjögren <st...@gmail.com>
>> wrote:
>>>
>>> Yeah, I think I found the thread already... by Timo Walther?
>>>
>>> On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen <se...@apache.org> wrote:
>>> > Would have been great. I had high hopes when I saw the trick with the
>>> > "constant pool", but this is only to make what Flink does already
>>> > applicable
>>> > to non-serializable lambdas.
>>> >
>>> > If you want to help us with this, I'll ping you for some support on the
>>> > OpenJDK mailing list ;-)
>>> >
>>> > On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <st...@gmail.com>
>>> > wrote:
>>> >>
>>> >> I suspected that you already had looked into this, but it was worth a
>>> >> try. It would make everything so much easier.
>>> >>
>>> >> Thanks for the explanation :-)
>>> >>
>>> >>
>>> >> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org>
>>> >> wrote:
>>> >> > Hi Kristoffer!
>>> >> >
>>> >> > I looked through the code as well. In fact, Flink currently uses the
>>> >> > trick
>>> >> > mentioned for Serializable Lambdas in the gist you sent me.
>>> >> >
>>> >> > This works well for lambdas that return simple types (primitives or
>>> >> > classes
>>> >> > without generics). The information for the generic parametrization
>>> >> > is
>>> >> > unfortunately really erased, it is in no signature or anything.
>>> >> >
>>> >> > Java has the concept of "generic method signatures", which means
>>> >> > that a
>>> >> > method gets a signature string that includes the generic types.
>>> >> > These
>>> >> > signatures are generated for regular functions, but OpenJDK and
>>> >> > OracleJDK do
>>> >> > not generate them for synthetic methods (like lambdas).
>>> >> >
>>> >> > We tried to submit a patch to OpenJDK to add these generic
>>> >> > signatures to
>>> >> > lambda methods, but they did not like the fact that we try to figure
>>> >> > out
>>> >> > the
>>> >> > generic types of lambdas. I hope they change their minds at some
>>> >> > point...
>>> >> >
>>> >> > Stephan
>>> >> >
>>> >> >
>>> >> >
>>> >> >
>>> >> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek
>>> >> > <al...@apache.org>
>>> >> > wrote:
>>> >> >>
>>> >> >> Unfortunately, this also doesn't work for the same reasons. The
>>> >> >> generic
>>> >> >> types of generic parameters of a lambda are not stored anywhere.
>>> >> >> Stephan
>>> >> >> mentioned to me that the only possibility right now would be to
>>> >> >> look at
>>> >> >> the
>>> >> >> code using something like ASM to find a cast in the code to the
>>> >> >> concrete
>>> >> >> type of the generic parameter.
>>> >> >>
>>> >> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com>
>>> >> >> wrote:
>>> >> >>>
>>> >> >>> How about https://github.com/jhalterman/typetools?
>>> >> >>>
>>> >> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
>>> >> >>> <al...@apache.org>
>>> >> >>> wrote:
>>> >> >>> > Hi Kristoffer,
>>> >> >>> > I'm afraid not, but maybe Timo has some further information. In
>>> >> >>> > this
>>> >> >>> > extended example we can see the problem:
>>> >> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The
>>> >> >>> > output
>>> >> >>> > is:
>>> >> >>> >
>>> >> >>> > Type is: class
>>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >> >>> > Type is: class
>>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >> >>> > Type is :
>>> >> >>> >
>>> >> >>> >
>>> >> >>> >
>>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
>>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >> >>> >
>>> >> >>> > So with the two lambda calls it does not correctly determine the
>>> >> >>> > generic
>>> >> >>> > parameter of Thing while it works with the anonymous class.
>>> >> >>> >
>>> >> >>> > I was exited when I saw the example because we've been trying
>>> >> >>> > for so
>>> >> >>> > long to
>>> >> >>> > get this to work. Maybe we have to wait for java 19 to get this
>>> >> >>> > to
>>> >> >>> > work. ;-)
>>> >> >>> >
>>> >> >>> > Thanks a lot for helping, though. :D
>>> >> >>> > Aljoscha
>>> >> >>> >
>>> >> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren
>>> >> >>> > <st...@gmail.com>
>>> >> >>> > wrote:
>>> >> >>> >>
>>> >> >>> >> Hi
>>> >> >>> >>
>>> >> >>> >> Potential fix for writing flink jobs using lamdas without
>>> >> >>> >> Eclipse
>>> >> >>> >> JDT?
>>> >> >>> >>
>>> >> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>>> >> >>> >>
>>> >> >>> >> Cheers,
>>> >> >>> >> -Kristoffer
>>> >> >
>>> >> >
>>> >
>>> >
>>
>>
>
Re: Java 8 and type erasure
Posted by Stephan Ewen <se...@apache.org>.
Yep, Timo wrote the patch, both for OpenJDK and JDT - the JDT one was
accepted in the end.
On Tue, Aug 18, 2015 at 2:09 PM, Robert Metzger <rm...@apache.org> wrote:
> Exactly, Timo opened the thread.
>
> On Tue, Aug 18, 2015 at 2:04 PM, Kristoffer Sjögren <st...@gmail.com>
> wrote:
>
>> Yeah, I think I found the thread already... by Timo Walther?
>>
>> On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen <se...@apache.org> wrote:
>> > Would have been great. I had high hopes when I saw the trick with the
>> > "constant pool", but this is only to make what Flink does already
>> applicable
>> > to non-serializable lambdas.
>> >
>> > If you want to help us with this, I'll ping you for some support on the
>> > OpenJDK mailing list ;-)
>> >
>> > On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <st...@gmail.com>
>> > wrote:
>> >>
>> >> I suspected that you already had looked into this, but it was worth a
>> >> try. It would make everything so much easier.
>> >>
>> >> Thanks for the explanation :-)
>> >>
>> >>
>> >> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org>
>> wrote:
>> >> > Hi Kristoffer!
>> >> >
>> >> > I looked through the code as well. In fact, Flink currently uses the
>> >> > trick
>> >> > mentioned for Serializable Lambdas in the gist you sent me.
>> >> >
>> >> > This works well for lambdas that return simple types (primitives or
>> >> > classes
>> >> > without generics). The information for the generic parametrization is
>> >> > unfortunately really erased, it is in no signature or anything.
>> >> >
>> >> > Java has the concept of "generic method signatures", which means
>> that a
>> >> > method gets a signature string that includes the generic types. These
>> >> > signatures are generated for regular functions, but OpenJDK and
>> >> > OracleJDK do
>> >> > not generate them for synthetic methods (like lambdas).
>> >> >
>> >> > We tried to submit a patch to OpenJDK to add these generic
>> signatures to
>> >> > lambda methods, but they did not like the fact that we try to figure
>> out
>> >> > the
>> >> > generic types of lambdas. I hope they change their minds at some
>> >> > point...
>> >> >
>> >> > Stephan
>> >> >
>> >> >
>> >> >
>> >> >
>> >> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <
>> aljoscha@apache.org>
>> >> > wrote:
>> >> >>
>> >> >> Unfortunately, this also doesn't work for the same reasons. The
>> generic
>> >> >> types of generic parameters of a lambda are not stored anywhere.
>> >> >> Stephan
>> >> >> mentioned to me that the only possibility right now would be to
>> look at
>> >> >> the
>> >> >> code using something like ASM to find a cast in the code to the
>> >> >> concrete
>> >> >> type of the generic parameter.
>> >> >>
>> >> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com>
>> >> >> wrote:
>> >> >>>
>> >> >>> How about https://github.com/jhalterman/typetools?
>> >> >>>
>> >> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
>> >> >>> <al...@apache.org>
>> >> >>> wrote:
>> >> >>> > Hi Kristoffer,
>> >> >>> > I'm afraid not, but maybe Timo has some further information. In
>> this
>> >> >>> > extended example we can see the problem:
>> >> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The
>> output
>> >> >>> > is:
>> >> >>> >
>> >> >>> > Type is: class
>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >> >>> > Type is: class
>> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >> >>> > Type is :
>> >> >>> >
>> >> >>> >
>> >> >>> >
>> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
>> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >> >>> >
>> >> >>> > So with the two lambda calls it does not correctly determine the
>> >> >>> > generic
>> >> >>> > parameter of Thing while it works with the anonymous class.
>> >> >>> >
>> >> >>> > I was exited when I saw the example because we've been trying
>> for so
>> >> >>> > long to
>> >> >>> > get this to work. Maybe we have to wait for java 19 to get this
>> to
>> >> >>> > work. ;-)
>> >> >>> >
>> >> >>> > Thanks a lot for helping, though. :D
>> >> >>> > Aljoscha
>> >> >>> >
>> >> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <
>> stoffe@gmail.com>
>> >> >>> > wrote:
>> >> >>> >>
>> >> >>> >> Hi
>> >> >>> >>
>> >> >>> >> Potential fix for writing flink jobs using lamdas without
>> Eclipse
>> >> >>> >> JDT?
>> >> >>> >>
>> >> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>> >> >>> >>
>> >> >>> >> Cheers,
>> >> >>> >> -Kristoffer
>> >> >
>> >> >
>> >
>> >
>>
>
>
Re: Java 8 and type erasure
Posted by Robert Metzger <rm...@apache.org>.
Exactly, Timo opened the thread.
On Tue, Aug 18, 2015 at 2:04 PM, Kristoffer Sjögren <st...@gmail.com>
wrote:
> Yeah, I think I found the thread already... by Timo Walther?
>
> On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen <se...@apache.org> wrote:
> > Would have been great. I had high hopes when I saw the trick with the
> > "constant pool", but this is only to make what Flink does already
> applicable
> > to non-serializable lambdas.
> >
> > If you want to help us with this, I'll ping you for some support on the
> > OpenJDK mailing list ;-)
> >
> > On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <st...@gmail.com>
> > wrote:
> >>
> >> I suspected that you already had looked into this, but it was worth a
> >> try. It would make everything so much easier.
> >>
> >> Thanks for the explanation :-)
> >>
> >>
> >> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org> wrote:
> >> > Hi Kristoffer!
> >> >
> >> > I looked through the code as well. In fact, Flink currently uses the
> >> > trick
> >> > mentioned for Serializable Lambdas in the gist you sent me.
> >> >
> >> > This works well for lambdas that return simple types (primitives or
> >> > classes
> >> > without generics). The information for the generic parametrization is
> >> > unfortunately really erased, it is in no signature or anything.
> >> >
> >> > Java has the concept of "generic method signatures", which means that
> a
> >> > method gets a signature string that includes the generic types. These
> >> > signatures are generated for regular functions, but OpenJDK and
> >> > OracleJDK do
> >> > not generate them for synthetic methods (like lambdas).
> >> >
> >> > We tried to submit a patch to OpenJDK to add these generic signatures
> to
> >> > lambda methods, but they did not like the fact that we try to figure
> out
> >> > the
> >> > generic types of lambdas. I hope they change their minds at some
> >> > point...
> >> >
> >> > Stephan
> >> >
> >> >
> >> >
> >> >
> >> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <
> aljoscha@apache.org>
> >> > wrote:
> >> >>
> >> >> Unfortunately, this also doesn't work for the same reasons. The
> generic
> >> >> types of generic parameters of a lambda are not stored anywhere.
> >> >> Stephan
> >> >> mentioned to me that the only possibility right now would be to look
> at
> >> >> the
> >> >> code using something like ASM to find a cast in the code to the
> >> >> concrete
> >> >> type of the generic parameter.
> >> >>
> >> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com>
> >> >> wrote:
> >> >>>
> >> >>> How about https://github.com/jhalterman/typetools?
> >> >>>
> >> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
> >> >>> <al...@apache.org>
> >> >>> wrote:
> >> >>> > Hi Kristoffer,
> >> >>> > I'm afraid not, but maybe Timo has some further information. In
> this
> >> >>> > extended example we can see the problem:
> >> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output
> >> >>> > is:
> >> >>> >
> >> >>> > Type is: class
> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >> >>> > Type is: class
> >> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >> >>> > Type is :
> >> >>> >
> >> >>> >
> >> >>> >
> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> >> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >> >>> >
> >> >>> > So with the two lambda calls it does not correctly determine the
> >> >>> > generic
> >> >>> > parameter of Thing while it works with the anonymous class.
> >> >>> >
> >> >>> > I was exited when I saw the example because we've been trying for
> so
> >> >>> > long to
> >> >>> > get this to work. Maybe we have to wait for java 19 to get this to
> >> >>> > work. ;-)
> >> >>> >
> >> >>> > Thanks a lot for helping, though. :D
> >> >>> > Aljoscha
> >> >>> >
> >> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <stoffe@gmail.com
> >
> >> >>> > wrote:
> >> >>> >>
> >> >>> >> Hi
> >> >>> >>
> >> >>> >> Potential fix for writing flink jobs using lamdas without Eclipse
> >> >>> >> JDT?
> >> >>> >>
> >> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
> >> >>> >>
> >> >>> >> Cheers,
> >> >>> >> -Kristoffer
> >> >
> >> >
> >
> >
>
Re: Java 8 and type erasure
Posted by Kristoffer Sjögren <st...@gmail.com>.
Yeah, I think I found the thread already... by Timo Walther?
On Tue, Aug 18, 2015 at 2:01 PM, Stephan Ewen <se...@apache.org> wrote:
> Would have been great. I had high hopes when I saw the trick with the
> "constant pool", but this is only to make what Flink does already applicable
> to non-serializable lambdas.
>
> If you want to help us with this, I'll ping you for some support on the
> OpenJDK mailing list ;-)
>
> On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <st...@gmail.com>
> wrote:
>>
>> I suspected that you already had looked into this, but it was worth a
>> try. It would make everything so much easier.
>>
>> Thanks for the explanation :-)
>>
>>
>> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org> wrote:
>> > Hi Kristoffer!
>> >
>> > I looked through the code as well. In fact, Flink currently uses the
>> > trick
>> > mentioned for Serializable Lambdas in the gist you sent me.
>> >
>> > This works well for lambdas that return simple types (primitives or
>> > classes
>> > without generics). The information for the generic parametrization is
>> > unfortunately really erased, it is in no signature or anything.
>> >
>> > Java has the concept of "generic method signatures", which means that a
>> > method gets a signature string that includes the generic types. These
>> > signatures are generated for regular functions, but OpenJDK and
>> > OracleJDK do
>> > not generate them for synthetic methods (like lambdas).
>> >
>> > We tried to submit a patch to OpenJDK to add these generic signatures to
>> > lambda methods, but they did not like the fact that we try to figure out
>> > the
>> > generic types of lambdas. I hope they change their minds at some
>> > point...
>> >
>> > Stephan
>> >
>> >
>> >
>> >
>> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <al...@apache.org>
>> > wrote:
>> >>
>> >> Unfortunately, this also doesn't work for the same reasons. The generic
>> >> types of generic parameters of a lambda are not stored anywhere.
>> >> Stephan
>> >> mentioned to me that the only possibility right now would be to look at
>> >> the
>> >> code using something like ASM to find a cast in the code to the
>> >> concrete
>> >> type of the generic parameter.
>> >>
>> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com>
>> >> wrote:
>> >>>
>> >>> How about https://github.com/jhalterman/typetools?
>> >>>
>> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek
>> >>> <al...@apache.org>
>> >>> wrote:
>> >>> > Hi Kristoffer,
>> >>> > I'm afraid not, but maybe Timo has some further information. In this
>> >>> > extended example we can see the problem:
>> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output
>> >>> > is:
>> >>> >
>> >>> > Type is: class
>> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >>> > Type is: class
>> >>> > org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >>> > Type is :
>> >>> >
>> >>> >
>> >>> > org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
>> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >>> >
>> >>> > So with the two lambda calls it does not correctly determine the
>> >>> > generic
>> >>> > parameter of Thing while it works with the anonymous class.
>> >>> >
>> >>> > I was exited when I saw the example because we've been trying for so
>> >>> > long to
>> >>> > get this to work. Maybe we have to wait for java 19 to get this to
>> >>> > work. ;-)
>> >>> >
>> >>> > Thanks a lot for helping, though. :D
>> >>> > Aljoscha
>> >>> >
>> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com>
>> >>> > wrote:
>> >>> >>
>> >>> >> Hi
>> >>> >>
>> >>> >> Potential fix for writing flink jobs using lamdas without Eclipse
>> >>> >> JDT?
>> >>> >>
>> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>> >>> >>
>> >>> >> Cheers,
>> >>> >> -Kristoffer
>> >
>> >
>
>
Re: Java 8 and type erasure
Posted by Stephan Ewen <se...@apache.org>.
Would have been great. I had high hopes when I saw the trick with the
"constant pool", but this is only to make what Flink does already
applicable to non-serializable lambdas.
If you want to help us with this, I'll ping you for some support on the
OpenJDK mailing list ;-)
On Tue, Aug 18, 2015 at 1:59 PM, Kristoffer Sjögren <st...@gmail.com>
wrote:
> I suspected that you already had looked into this, but it was worth a
> try. It would make everything so much easier.
>
> Thanks for the explanation :-)
>
>
> On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org> wrote:
> > Hi Kristoffer!
> >
> > I looked through the code as well. In fact, Flink currently uses the
> trick
> > mentioned for Serializable Lambdas in the gist you sent me.
> >
> > This works well for lambdas that return simple types (primitives or
> classes
> > without generics). The information for the generic parametrization is
> > unfortunately really erased, it is in no signature or anything.
> >
> > Java has the concept of "generic method signatures", which means that a
> > method gets a signature string that includes the generic types. These
> > signatures are generated for regular functions, but OpenJDK and
> OracleJDK do
> > not generate them for synthetic methods (like lambdas).
> >
> > We tried to submit a patch to OpenJDK to add these generic signatures to
> > lambda methods, but they did not like the fact that we try to figure out
> the
> > generic types of lambdas. I hope they change their minds at some point...
> >
> > Stephan
> >
> >
> >
> >
> > On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <al...@apache.org>
> > wrote:
> >>
> >> Unfortunately, this also doesn't work for the same reasons. The generic
> >> types of generic parameters of a lambda are not stored anywhere. Stephan
> >> mentioned to me that the only possibility right now would be to look at
> the
> >> code using something like ASM to find a cast in the code to the concrete
> >> type of the generic parameter.
> >>
> >> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com>
> wrote:
> >>>
> >>> How about https://github.com/jhalterman/typetools?
> >>>
> >>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek <
> aljoscha@apache.org>
> >>> wrote:
> >>> > Hi Kristoffer,
> >>> > I'm afraid not, but maybe Timo has some further information. In this
> >>> > extended example we can see the problem:
> >>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output
> is:
> >>> >
> >>> > Type is: class
> org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> > Type is: class
> org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> > Type is :
> >>> >
> >>> >
> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> >>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >>> >
> >>> > So with the two lambda calls it does not correctly determine the
> >>> > generic
> >>> > parameter of Thing while it works with the anonymous class.
> >>> >
> >>> > I was exited when I saw the example because we've been trying for so
> >>> > long to
> >>> > get this to work. Maybe we have to wait for java 19 to get this to
> >>> > work. ;-)
> >>> >
> >>> > Thanks a lot for helping, though. :D
> >>> > Aljoscha
> >>> >
> >>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com>
> >>> > wrote:
> >>> >>
> >>> >> Hi
> >>> >>
> >>> >> Potential fix for writing flink jobs using lamdas without Eclipse
> JDT?
> >>> >>
> >>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
> >>> >>
> >>> >> Cheers,
> >>> >> -Kristoffer
> >
> >
>
Re: Java 8 and type erasure
Posted by Kristoffer Sjögren <st...@gmail.com>.
I suspected that you already had looked into this, but it was worth a
try. It would make everything so much easier.
Thanks for the explanation :-)
On Tue, Aug 18, 2015 at 1:50 PM, Stephan Ewen <se...@apache.org> wrote:
> Hi Kristoffer!
>
> I looked through the code as well. In fact, Flink currently uses the trick
> mentioned for Serializable Lambdas in the gist you sent me.
>
> This works well for lambdas that return simple types (primitives or classes
> without generics). The information for the generic parametrization is
> unfortunately really erased, it is in no signature or anything.
>
> Java has the concept of "generic method signatures", which means that a
> method gets a signature string that includes the generic types. These
> signatures are generated for regular functions, but OpenJDK and OracleJDK do
> not generate them for synthetic methods (like lambdas).
>
> We tried to submit a patch to OpenJDK to add these generic signatures to
> lambda methods, but they did not like the fact that we try to figure out the
> generic types of lambdas. I hope they change their minds at some point...
>
> Stephan
>
>
>
>
> On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <al...@apache.org>
> wrote:
>>
>> Unfortunately, this also doesn't work for the same reasons. The generic
>> types of generic parameters of a lambda are not stored anywhere. Stephan
>> mentioned to me that the only possibility right now would be to look at the
>> code using something like ASM to find a cast in the code to the concrete
>> type of the generic parameter.
>>
>> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com> wrote:
>>>
>>> How about https://github.com/jhalterman/typetools?
>>>
>>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek <al...@apache.org>
>>> wrote:
>>> > Hi Kristoffer,
>>> > I'm afraid not, but maybe Timo has some further information. In this
>>> > extended example we can see the problem:
>>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output is:
>>> >
>>> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> > Type is :
>>> >
>>> > org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
>>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>>> >
>>> > So with the two lambda calls it does not correctly determine the
>>> > generic
>>> > parameter of Thing while it works with the anonymous class.
>>> >
>>> > I was exited when I saw the example because we've been trying for so
>>> > long to
>>> > get this to work. Maybe we have to wait for java 19 to get this to
>>> > work. ;-)
>>> >
>>> > Thanks a lot for helping, though. :D
>>> > Aljoscha
>>> >
>>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com>
>>> > wrote:
>>> >>
>>> >> Hi
>>> >>
>>> >> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>>> >>
>>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>>> >>
>>> >> Cheers,
>>> >> -Kristoffer
>
>
Re: Java 8 and type erasure
Posted by Stephan Ewen <se...@apache.org>.
Hi Kristoffer!
I looked through the code as well. In fact, Flink currently uses the trick
mentioned for Serializable Lambdas in the gist you sent me.
This works well for lambdas that return simple types (primitives or classes
without generics). The information for the generic parametrization is
unfortunately really erased, it is in no signature or anything.
Java has the concept of "generic method signatures", which means that a
method gets a signature string that includes the generic types. These
signatures are generated for regular functions, but OpenJDK and OracleJDK
do not generate them for synthetic methods (like lambdas).
We tried to submit a patch to OpenJDK to add these generic signatures to
lambda methods, but they did not like the fact that we try to figure out
the generic types of lambdas. I hope they change their minds at some
point...
Stephan
On Tue, Aug 18, 2015 at 11:46 AM, Aljoscha Krettek <al...@apache.org>
wrote:
> Unfortunately, this also doesn't work for the same reasons. The generic
> types of generic parameters of a lambda are not stored anywhere. Stephan
> mentioned to me that the only possibility right now would be to look at the
> code using something like ASM to find a cast in the code to the concrete
> type of the generic parameter.
>
> On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com> wrote:
>
>> How about https://github.com/jhalterman/typetools?
>>
>> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek <al...@apache.org>
>> wrote:
>> > Hi Kristoffer,
>> > I'm afraid not, but maybe Timo has some further information. In this
>> > extended example we can see the problem:
>> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output is:
>> >
>> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> > Type is :
>> > org.apache.flink.examples.java8.wordcount.TypeTest.org
>> .apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
>> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>> >
>> > So with the two lambda calls it does not correctly determine the generic
>> > parameter of Thing while it works with the anonymous class.
>> >
>> > I was exited when I saw the example because we've been trying for so
>> long to
>> > get this to work. Maybe we have to wait for java 19 to get this to
>> work. ;-)
>> >
>> > Thanks a lot for helping, though. :D
>> > Aljoscha
>> >
>> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com>
>> wrote:
>> >>
>> >> Hi
>> >>
>> >> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>> >>
>> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>> >>
>> >> Cheers,
>> >> -Kristoffer
>>
>
Re: Java 8 and type erasure
Posted by Aljoscha Krettek <al...@apache.org>.
Unfortunately, this also doesn't work for the same reasons. The generic
types of generic parameters of a lambda are not stored anywhere. Stephan
mentioned to me that the only possibility right now would be to look at the
code using something like ASM to find a cast in the code to the concrete
type of the generic parameter.
On Tue, 18 Aug 2015 at 11:35 Kristoffer Sjögren <st...@gmail.com> wrote:
> How about https://github.com/jhalterman/typetools?
>
> On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek <al...@apache.org>
> wrote:
> > Hi Kristoffer,
> > I'm afraid not, but maybe Timo has some further information. In this
> > extended example we can see the problem:
> > https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output is:
> >
> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> > Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> > Type is :
> > org.apache.flink.examples.java8.wordcount.TypeTest.org
> .apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> > class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> >
> > So with the two lambda calls it does not correctly determine the generic
> > parameter of Thing while it works with the anonymous class.
> >
> > I was exited when I saw the example because we've been trying for so
> long to
> > get this to work. Maybe we have to wait for java 19 to get this to work.
> ;-)
> >
> > Thanks a lot for helping, though. :D
> > Aljoscha
> >
> > On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com>
> wrote:
> >>
> >> Hi
> >>
> >> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
> >>
> >> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
> >>
> >> Cheers,
> >> -Kristoffer
>
Re: Java 8 and type erasure
Posted by Kristoffer Sjögren <st...@gmail.com>.
How about https://github.com/jhalterman/typetools?
On Tue, Aug 18, 2015 at 11:16 AM, Aljoscha Krettek <al...@apache.org> wrote:
> Hi Kristoffer,
> I'm afraid not, but maybe Timo has some further information. In this
> extended example we can see the problem:
> https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output is:
>
> Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
> Type is :
> org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
> class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
>
> So with the two lambda calls it does not correctly determine the generic
> parameter of Thing while it works with the anonymous class.
>
> I was exited when I saw the example because we've been trying for so long to
> get this to work. Maybe we have to wait for java 19 to get this to work. ;-)
>
> Thanks a lot for helping, though. :D
> Aljoscha
>
> On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com> wrote:
>>
>> Hi
>>
>> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>>
>> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>>
>> Cheers,
>> -Kristoffer
Re: Java 8 and type erasure
Posted by Aljoscha Krettek <al...@apache.org>.
Hi Kristoffer,
I'm afraid not, but maybe Timo has some further information. In this
extended example we can see the problem:
https://gist.github.com/aljoscha/84cc363d13cf1dfe9364. The output is:
Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
Type is: class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
Type is :
org.apache.flink.examples.java8.wordcount.TypeTest.org.apache.flink.examples.java8.wordcount.TypeTest$Thing<java.lang.String>
class org.apache.flink.examples.java8.wordcount.TypeTest$Thing
So with the two lambda calls it does not correctly determine the generic
parameter of Thing while it works with the anonymous class.
I was exited when I saw the example because we've been trying for so long
to get this to work. Maybe we have to wait for java 19 to get this to work.
;-)
Thanks a lot for helping, though. :D
Aljoscha
On Tue, 18 Aug 2015 at 11:01 Kristoffer Sjögren <st...@gmail.com> wrote:
> Hi
>
> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>
> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>
> Cheers,
> -Kristoffer
>
Re: Java 8 and type erasure
Posted by Kristoffer Sjögren <st...@gmail.com>.
:-)
On Tue, Aug 18, 2015 at 11:03 AM, Stephan Ewen <se...@apache.org> wrote:
> Wow, that looks super interesting.
>
> Will try that out later.
>
> Thanks for sharing :-)
>
> On Tue, Aug 18, 2015 at 11:01 AM, Kristoffer Sjögren <st...@gmail.com>
> wrote:
>>
>> Hi
>>
>> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>>
>> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>>
>> Cheers,
>> -Kristoffer
>
>
Re: Java 8 and type erasure
Posted by Stephan Ewen <se...@apache.org>.
Wow, that looks super interesting.
Will try that out later.
Thanks for sharing :-)
On Tue, Aug 18, 2015 at 11:01 AM, Kristoffer Sjögren <st...@gmail.com>
wrote:
> Hi
>
> Potential fix for writing flink jobs using lamdas without Eclipse JDT?
>
> https://gist.github.com/aslakhellesoy/3678beba60c109eacbe5
>
> Cheers,
> -Kristoffer
>