Support both Jackson 2 and 3 custom JSON mapper

[onobc]

In version 2.0 we simply documented the fact that you have to use Jackson 2 ObjectMapper if you want use the custom JSON mapper feature in Spring Pulsar (summary comment).

Implementation details

Ideally, we want to support both Jackson 2 ObjectMapper and Jackson 3 JsonMapper (similar to spring-data-commons).

The trick is that Pulsar proper does not support Jackson 3 (nor is it on the roadmap). I have not dug deep enough to see if we can use JsonMapper (i.e. i'm not sure where the Jackson 2 vs. Jackson 3 membrane resides - so to speak).

Here are the current touch points where we will need operate on:

Messages

Pulsar message custom mapping.

Here is a rough code call chain (i.e. important points to check out):

NOTE: User must customize the DSR to "set the om on dsr"

DefaultSchemaResolver#jsonSchemaForMessageType
	if (om set on dsr)
		JSONSchemaUtil.schemaForTypeWithObjectMapper(type, om)

If you need a schema instance using a custom om - you must call JSONSchemaUtil yourself

Message headers

Pulsar message header custom mapping.

Here is a rough code call chain (i.e. important points to check out):

Pulsar(Listener|Reader)AnnotationBeanPostProcessor#postProcessEndpointsBeforeRegistration

	PulsarHeaderObjectMapperUtils.customMapper(this.requireNonNullBeanFactory())
		.ifPresent((objectMapper) -> this.processedEndpoints
			.forEach((endpoint) -> endpoint.setObjectMapper(objectMapper)));


PulsarHeaderObjectMapperUtils#customMapper
	looks up OM w/ bean name "pulsarHeaderObjectMapper"

MethodPulsarListenerEndpoint#setObjectMapper
MethodPulsarReaderEndpoint#setObjectMapper

AbstractPulsarMessageToSpringMessageAdapter#setObjectMapper

NOTE: User must set om on the JPHMB JsonPulsarHeaderMapperBuilder#objectMapper 

[onobc]

cc: @therepanic

[therepanic]

Hi, @onobc. Sorry for being so late, as I saw this issue a bit late. I was already considering using Jackson 3 and Jackson 2 in this issue #1151 and was researching this.

Basically, we need to implement support for both Jackson 3 and Jackson 2, similar to spring-data-common? I assume it won't be much different? Is this issue open for development? Could I dig deeper into this issue and work on it?

[onobc]

Hi @therepanic ,

Oh no worries. Perfect timing actually. This is open for dev. It is similar to SDC in that the technique to have a 2 or 3 will use a parallel hierarchy of components (one using old ObjectMapper and one using new JsonMapper) and will switch on/off based on which is enabled using a ClassUtils (likely).

However, the "areas" or "components" where this needs to happen for Spring Pulsar are outlined in issue description. Let me know if you have any questions around those details etc..

Thank you.

[onobc]

Hi @therepanic ,

A couple of thoughts..

The 1st thing I would do is get an understanding of the current touch points w/ JSON in Spring Pulsar

• Pulsar message custom mapping
• Pulsar message header custom mapping

Once the current touch points are understood, I would verify that Jackson3 on client will work w/ Jackson2 on server. I would expect it would be fine since we already support a custom Jackson 2 object mapper (which seems like a similar situation - its different than what is used on the server or internally in the client. This is what I meant w/ the

The trick is that Pulsar proper does not support Jackson 3 (nor is it on the roadmap). I have not dug deep enough to see if we can use JsonMapper (i.e. i'm not sure where the Jackson 2 vs. Jackson 3 membrane resides - so to speak).