Migration Java to Jackson serialization

Akka
1

Hey.
My project is using java serializer. I am migrating to akka 2.6

My message classes is used as below with java serializer.
public class MyMessage implements Serializable
serializers {
** java = “akka.serialization.JavaSerializer”**
** jackson-json = “akka.serialization.jackson.JacksonJsonSerializer”**
** }**
** serialization-bindings {**
** “com.my.MyMessage” = java**
** }**

I modified as described.
(https://doc.akka.io/docs/akka/current/additional/rolling-updates.html#from-java-serialization-to-jackson)

public class MyMessage implements Serializable, MySerializable
serializers {
** java = “akka.serialization.JavaSerializer”**
** jackson-json = “akka.serialization.jackson.JacksonJsonSerializer”**
** }**
** serialization-bindings {**
** “com.my.MyMessage” = java**
** }**

but, It cannot work. I can’t understand this comment.
Change message classes by adding the marker interface and possibly needed annotations as described in Serialization with Jackson.

How can old cluster deserialize java/jackson in 2nd step? Please explain in detail.

2

That is what you have done in:

public class MyMessage implements Serializable, MySerializable

The marker interface is MySerializable. That is what you will later add to serialization-bindings instead of the java binding:

serialization-bindings {
  "com.my. MySerializable" = jackson-json
}

I don’t think you should have "com.my.MyMessage" = java in the bindings in the first place because that is already covered by java.io.Serializable binding.

In 2nd step there will be no Jackson serialization/deserialization because MySerializable has not been added to the bindings (for serialization/toBinary) yet.

In 3rd step the new cluster nodes will start using Jackson for serialization/toBinary and when those messages are received the old cluster nodes are prepared to deserialize those given the changes in 2nd step.

When writing this I realize that we might have missed one thing in that description. 2nd step might need config:

akka.serialization.jackson.whitelist-class-prefix = ["com.my.MyMessage"]

I’ll test that and let you know if that is also needed.

What error did you see, or what was it that didn’t work?

3

Thanks for your kind explanation.
I missed this like your mention.
Really appreciate it.

akka.serialization.jackson.whitelist-class-prefix = [“com.my.MyMessage”]

4

I have verified that the whitelist is needed and missing in the instructions. Documentation will be updated in next version.

akka.serialization.jackson.whitelist-class-prefix=["com.myapp"]

is needed in step 2. Replace com.myapp with the name of the root package of your application to trust all classes. This is needed for Jackson deserialization when the serialization-bindings isn’t defined.

The whitelist can be removed in step 3, because then it’s defined in the serialization-bindings.

Thanks for reporting.

5

Hello @patriknw ,
sorry for digging out such old thread :-)
step 2 “adding the marker interface” would already break java serialization for case classes which did not yet have the explicit SerialVersionUID annotation, right?
So step 1 should include “add SerialVersionUID to all message classes that are candidates for adding the marker interface in step 2”.
Correct?