JsonDeserializer constructor with TypeReference argument

[pavelpe]

Couldn't find any way to construct JsonDeserializer with TypeReference argument.
The only way is Class <T> targetType but ObjectMapper instance (default) which is initialized inside deserializer has readerFor(TypeReference<?> type) for a long time already.

Building custom ObjectMapper feels like workaround in such case.

Is there any specific reason why JsonDeserializer does not provide such constructor?

[artembilan]

I don't see how a custom ObjectMapper can be as a workaround, but this is a good request for the improvement.

We definitely can add a bunch of new constructors to apply TypeReference.

I see another way via headers:

ObjectReader deserReader = null;
if (this.typeMapper.getTypePrecedence().equals(TypePrecedence.TYPE_ID)) {
	JavaType javaType = this.typeMapper.toJavaType(headers);
	if (javaType != null) {
		deserReader = this.objectMapper.readerFor(javaType);
	}
}

But if there is no type info in the headers, there is no way to interact with the TypeReference...

Please, share your experience on the matter meanwhile we are introducing those new constructors.

Thanks

[pavelpe]

I don't see how a custom ObjectMapper can be as a workaround, but this is a good request for the improvement.

Yes you are right, there is no way to pass ObjectMapper directly via ctors.
The idea (theoretically) was to pass custom ObjectMapper with custom ObjectReader into JsonDeser to be used at this stage:

if (this.reader == null) {
   this.reader = this.objectMapper.readerFor(this.targetType);
}

But eventually I haven't tried this approach so I didn't pay attention to protected access modifier at:

protected JsonDeserializer(ObjectMapper objectMapper)

Thanks for provided example

I see anothekr way via headers:

ObjectReader deserReader = null;
if (this.typeMapper.getTypePrecedence().equals(TypePrecedence.TYPE_ID)) {
	JavaType javaType = this.typeMapper.toJavaType(headers);
	if (javaType != null) {
		deserReader = this.objectMapper.readerFor(javaType);
	}
}

But if there is no type info in the headers, there is no way to interact with the TypeReference...

but it is not an option in my case because headers are omitted on the send.

I was trying to implement generic consumer (not aware of multiple consumed topics types).
The simplest solution I came about was to init targetType to Object class with ConsumerRecord type in @KafkaListener method.
But when new ctors will be available, I would switch to TypeReference approach. It seems more elegant to me.

Thanks.

[artembilan]

I think all good now. We are going to release 2.3 M1 this week or early next week.