serialization docs out of date for JSON format
Eckart Hertzler
while playing with wicket and akka (and cassandra), I noticed that the serialization doc is somewhat out of date.
the docs (http://doc.akkasource.org/serialization) tell me that:
------------------------------------------------------------------------
If you are sending messages to a remote Actor/Active Object and these messages are implementing one of the predefined interfaces/traits in the 'se.scalablesolutions.akka.serialization.Serialization.*' object, then Akka will transparently detect which serialization format it should use as wire protocol and will automatically serialize and deserialize the message according to this protocol.
Each serialization interface/trait in
* se.scalablesolutions.akka.serialization.Serialization.*
has a matching serializer in
* se.scalablesolutions.akka.serialization.Serializer.*.
------------------------------------------------------------------------
But It seems that se.scalablesolutions.akka.serialization.Serialization.* is no more...
------------------------------------------------------------------------
scala> import se.scalablesolutions.akka.serialization.Serialization._
<console>:4: error: value Serialization is not a member of package se.scalablesolutions.akka.serialization
import se.scalablesolutions.akka.serialization.Serialization._
^
scala> import se.scalablesolutions.akka.serialization.Serializer
import se.scalablesolutions.akka.serialization.Serializer
----------------------------------------------------------------------
Furthermore the example for JSON: Scala does not work:
-----------
scala> import se.scalablesolutions.akka.serialization.Serializable.ScalaJSON
import se.scalablesolutions.akka.serialization.Serializable.ScalaJSON
scala> case class MyMessage(val id: String, val value: Tuple2[String, Int]) extends ScalaJSON
defined class MyMessage
scala> val message = MyMessage("id", ("hello", 34))
message: MyMessage = MyMessage(id,(hello,34))
scala> val json = message.toJSON
java.lang.UnsupportedOperationException: Class class MyMessage not supported for conversion
at sjson.json.JsBean$class.toJSON(JsBean.scala:193)
at sjson.json.Serializer$SJSON$.toJSON(Serializer.scala:107)
at sjson.json.Serializer$SJSON$class.out(Serializer.scala:37)
at sjson.json.Serializer$SJSON$.out(Serializer.scala:107)
at se.scalablesolutions.akka.serialization.Serializable$S...
scala>
----------------
I can fix this by adding the @BeanInfo annotation.
but the deserialization in the second example yields this:
-----------------------------------------------
scala> @BeanInfo case class Foo()
defined class Foo
scala> val foo = new Foo()
foo: Foo = Foo()
scala> val json = Serializer.ScalaJSON.out(foo)
java.lang.UnsupportedOperationException: Class class Foo not supported for conversion
at sjson.json.JsBean$class.toJSON(JsBean.scala:193)
at sjson.json.Serializer$SJSON$.toJSON(Serializer.scala:107)
at sjson.json.Serializer$SJSON$class.out(Serializer.scala:37)
at sjson.json.Serializer$SJSON$.out(Serializer.scala:107)
at se.scalablesolutions.akka.serialization.Serializer$ScalaJSON...
-----------------------
ok, it seems the case class needs at least one attribute:
------------------------
scala> @BeanInfo case class Foo(name: String)
defined class Foo
scala> val foo = new Foo("foo")
foo: Foo = Foo(foo)
scala> val json = Serializer.ScalaJSON.out(foo)
json: Array[Byte] = Array(123, 34, 110, 97, 109, 101, 34, 58, 34, 102, 111, 111, 34, 125)
scala> val fooCopy = Serializer.ScalaJSON.in(json).asInstanceOf[Foo]
<console>:10: error: type mismatch;
found : Array[Byte]
required: String
val fooCopy = Serializer.ScalaJSON.in(json).asInstanceOf[Foo]
^
---------------------------
ok, so I give it a string.
But then...
--------------------------
scala> val fooCopy = Serializer.ScalaJSON.in(new String(json)).asInstanceOf[Foo]
java.lang.ClassCastException: dispatch.json.JsObject cannot be cast to Foo
at .<init>(<console>:10)
at .<clinit>(<console>)
at RequestResult$.<init>(<console>:3)
at RequestResult$.<clinit>(<console>)
at RequestResult$result(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
...
scala>
-------------------------
Now, I could fix the sample code (in a way), but I don't know enough to fix the bit about the missing Serialization class.
- Eckart
Debasish Ghosh
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Jonas Bonér
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Eckart Hertzler
> Hi -
>
> Regarding the JSON problem that you faced, could you pls try the current
> trunk version from Akka Github. I got the same problem reported sometime
> back and fixed it in the trunk.
>
That was the current trunk version. So, alas, the problem does not go away ...
Anyhow, I can see the problem in the source..
1. the Serialization class does not exist
2. sjson.json.Serializer.in does have a type parameter that returns a properly constructed Foo,
but se.scalablesolutions.akka.serialization.Serializer.ScalaJSON does not.
Otherwise its just minor inconsistencies in the documentation.
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Eckart Hertzler
> Thanks for the report. I'll fix the docs tomorrow.
no problem.
I can fix the sample code myself, if you like...
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Debasish Ghosh
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Jonas Bonér
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Jonas Bonér
twitter: @jboner
blog: http://jonasboner.com
work: http://scalablesolutions.se
code: http://github.com/jboner
code: http://akkasource.org
also: http://letitcrash.com
Debasish Ghosh
Also I need to fix a bug in sjson which I detected in de-serialization of Tuple2, which I plan to do later. Erasure is turning out to be a serious problem now. Plus deserializing from a narrower language (JSON) into one with a large range of types (Scala) is also creating lots of problems. And workarounds are not pleasing either.
Thanks.
- Debasish
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
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Jonas Bonér
Eckart Hertzler
> Thanks a lot Debasish.
>
> Eckhart, did you change the docs?
>
Yep.
Just now.
> > Debasish Ghosh
> > http://manning.com/ghosh
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Eckart Hertzler
> I have fixed the issue with Serializer.scala in
> se.scalablesolutions.akka.serializer. I will check it in the master later
> today.
>
sounds good. I am looking forward to it.
Eckart
Jonas Bonér
Eckart Hertzler
> Thanks Eckhart.
>
my pleasure
:-)
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