Looked up serializer contains incompletely configured ObjectIdWriter

The following test case

class SerializerLookupTest {

	@Test
	void lookedUpSerializerSerializesObjectId() throws Exception {

		ObjectMapper mapper = new ObjectMapper();

		SerializerProvider serializers = mapper.getSerializerProviderInstance();
		JsonSerializer<Object> serializer = serializers.findValueSerializer(Sample.class);

		serializer.serialize(new Sample(), mapper.getFactory().createGenerator(System.out), serializers);
	}

	@JsonIdentityInfo(generator = ObjectIdGenerators.UUIDGenerator.class, property = "@jsonObjectId")
	public class Sample {}
}

fails with:

ava.lang.NullPointerException
    at com.fasterxml.jackson.databind.ser.impl.WritableObjectId.writeAsField(WritableObjectId.java:79)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase._serializeWithObjectId(BeanSerializerBase.java:678)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:171)
    at dcs.spring.hateoas.poc.endpoint.SerializerLookupTest.lookedUpSerializerSerializesObjectId(SerializerLookupTest.java:39)

The gist of it is that serializers looked up from the SerializerProvider contain incompletely configured ObjectIdWriter instances (essentially the serializer held in it is null, likely because ObjectIdWriter.construct(…) initializes it with null). One way to make this work is to invoke ….createContextual(providers, null) but, I’d argue, that either the serializer should be properly initialized right away or the serialization of the object id has to be able to deal with the fact that the underlying serializer is null.

[cowtowncoder]

Right, implement ContextualSerializer does make serializer get callback method called during its contextualization.

I mostly mentioned delegating base type as possible inspiration, to help implement what you need. It may or may not be useful on its own.

One caveat on createContextual() is that it can get called multiple times on “blueprint” serializer instance: so if any changes are needed, a fresh new instance of the serializer must be constructed. This is different from resolve() method of ResolvableSerializer (which is rarely if ever needed by non-POJO serializers) which has to modify instance directly (and has different semantics).

[cowtowncoder]

Ok, at this point I should probably just document that non-Jackson code should never try to construct a SerializerProvider, ever. This is not an extension point meant for external use: it is only there to be used for various writeValue() calls.

Instead, SerialierProvider should be provided as part of context for all calls where it may be needed.