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Date: Wed, 23 Sep 2015 13:37:46 +0200
Message-ID: 
 <CANC1h_vVOK+O6HNbmMy15Dz_D27OMoLE+ND1roNF4uXJX2+UWA@mail.gmail.com>
Subject: Re: Immutable data
From: Stephan Ewen <sewen@apache.org>
To: user@flink.apache.org
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Hi Jack!

This should be supported, there is no strict requirement for mutable types.

The POJO rules apply only if you want to use the "by-field-name" addressing
for keys. In Scala, you should be able to use case classes as well, even if
they are immutable.

Can you post the exception that you get?

Greetings,
Stephan


On Wed, Sep 23, 2015 at 1:29 PM, Jack <jack-knilf@marmelandia.com> wrote:

> Hi,
>
> I'm having trouble integrating existing Scala code with Flink, due to
> POJO-only requirement.
>
> We're using AnyVal heavily for type safety, and immutable classes as a
> default. For example, the following does not work:
>
> object Test {
>   class Id(val underlying: Int) extends AnyVal
>
>   class X(var id: Id) {
>     def this() { this(new Id(0)) }
>   }
>
>   class MySource extends SourceFunction[X] {
>     def run(ctx: SourceFunction.SourceContext[X]) {
>       ctx.collect(new X(new Id(1)))
>     }
>     def cancel() {}
>   }
>
>   def main(args: Array[String]) {
>     val env = StreamExecutionContext.getExecutionContext
>     env.addSource(new MySource).print
>     env.execute("Test")
>   }
> }
>
> Currently I'm thinking that I would need to have duplicate classes and
> code for Flint and for non-Flint code, or somehow use immutable interfaces
> for non-Flint code. Both ways are expensive in terms of development time.
>
> Would you have any guidance on how to integrate Flink with a code base
> that has immutability as a norm?
>
> Thanks

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<div dir=3D"ltr">Hi Jack!<div><br></div><div>This should be supported, ther=
e is no strict requirement for mutable types.</div><div><br></div><div>The =
POJO rules apply only if you want to use the &quot;by-field-name&quot; addr=
essing for keys. In Scala, you should be able to use case classes as well, =
even if they are immutable.</div><div><br></div><div>Can you post the excep=
tion that you get?</div><div><br></div><div>Greetings,<br>Stephan</div><div=
><br></div></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">=
On Wed, Sep 23, 2015 at 1:29 PM, Jack <span dir=3D"ltr">&lt;<a href=3D"mail=
to:jack-knilf@marmelandia.com" target=3D"_blank">jack-knilf@marmelandia.com=
</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
I&#39;m having trouble integrating existing Scala code with Flink, due to P=
OJO-only requirement.<br>
<br>
We&#39;re using AnyVal heavily for type safety, and immutable classes as a =
default. For example, the following does not work:<br>
<br>
object Test {<br>
=C2=A0 class Id(val underlying: Int) extends AnyVal<br>
<br>
=C2=A0 class X(var id: Id) {<br>
=C2=A0 =C2=A0 def this() { this(new Id(0)) }<br>
=C2=A0 }<br>
<br>
=C2=A0 class MySource extends SourceFunction[X] {<br>
=C2=A0 =C2=A0 def run(ctx: SourceFunction.SourceContext[X]) {<br>
=C2=A0 =C2=A0 =C2=A0 ctx.collect(new X(new Id(1)))<br>
=C2=A0 =C2=A0 }<br>
=C2=A0 =C2=A0 def cancel() {}<br>
=C2=A0 }<br>
<br>
=C2=A0 def main(args: Array[String]) {<br>
=C2=A0 =C2=A0 val env =3D StreamExecutionContext.getExecutionContext<br>
=C2=A0 =C2=A0 env.addSource(new MySource).print<br>
=C2=A0 =C2=A0 env.execute(&quot;Test&quot;)<br>
=C2=A0 }<br>
}<br>
<br>
Currently I&#39;m thinking that I would need to have duplicate classes and =
code for Flint and for non-Flint code, or somehow use immutable interfaces =
for non-Flint code. Both ways are expensive in terms of development time.<b=
r>
<br>
Would you have any guidance on how to integrate Flink with a code base that=
 has immutability as a norm?<br>
<br>
Thanks</blockquote></div><br></div>

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