Afterburner breaks serialization of ObjectMapper

[zman0900]

JsonMapper and its parent class ObjectMapper are both supposed to be Serializable, but when AfterburnerModule is added, serialization is no longer possible.

For example, this code:

public class SerTest {
    public static void main(final String... args) throws Exception {
        final JsonMapper x = JsonMapper.builder()
                .addModule(new AfterburnerModule())
                .build();

        final ByteArrayOutputStream out = new ByteArrayOutputStream();
        new ObjectOutputStream(out)
                .writeObject(x);

        final ObjectInputStream input = new ObjectInputStream(new ByteArrayInputStream(out.toByteArray()));
        final JsonMapper y = (JsonMapper) input.readObject();
    }
}

Results in exception:

Exception in thread "main" java.io.NotSerializableException: com.fasterxml.jackson.module.afterburner.deser.DeserializerModifier
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
	at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at SerTest.main(SerTest.java:13)

Without adding the AfterburnerModule to JsonMapper, this works as expected.

Jackson version = 2.11.0

[cowtowncoder]

Thank you for reporting this: yes, modules should be serializable (there is one known exception for 2.x, Java 8 date/time module; but those are exceptions to the rule and Afterburner not known as one).

One quick question: do you know if this is a regression (used to work), or just observed now?

[cowtowncoder]

Ok. So, was able to make serializability work in 2.11(.1) as long as ObjectMapper serialized BEFORE any use of Afterburner (that is, readValue, writeValue that triggers class generation).
This is the general best practice anyway (serializable after configuration, before use) but I thought it good to mention.

Jackson 3.0 will actually change the limit as JDK serialization of ObjectMapper is limited to only serializing configuration, not state (based on big refactoring of how construction of mapper works with builders): it will not matter if usage has occurred. But 2.x has this limitation.

[zman0900]

I've never tried it in previous versions. I've worked around it for now by just using a static variable. I was trying to have Spring create and configure the JsonMapper, which would then be used in a map function for Spark, but those must be serializable.

[cowtowncoder]

@zman0900 Makes sense. Serializing ObjectMapper is often best avoided but intent is for JDK serialization to work for mapper, modules, as sometimes it is still needed.

As per my notes this will be fixed in 2.11.1, as long as pattern of config-only-before-serialization/deserialization is followed.