ErrorHandlingJsonSerializer2 configuration shortcoming

[dipeti]

Quote from documentation of 2.2.2.RELEASE:
If the delegate fails to deserialize the record content, the ErrorHandlingDeserializer2 returns a null value and a DeserializationException in a header, containing the cause and raw bytes. When using a record-level MessageListener, if either the key or value contains a DeserializationException header, the container’s ErrorHandler is called with the failed ConsumerRecord; the record is not passed to the listener.

This all works perfect if I configure my ConsumerFactory as described in the docs:

public ConsumerFactory<?, ?> consumerFactoryFromDocs() {
        Map<String, Object> props = new HashMap<>()
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, ErrorHandlingDeserializer2.class);
        props.put(ErrorHandlingDeserializer.KEY_DESERIALIZER_CLASS, JsonDeserializer.class);
        return new DefaultKafkaConsumerFactory<>(props);
}

However, I have configured my application in a slightly different way, which should arguably lead to the same settings but it does not.

public ConsumerFactory<?, ?> consumerFactoryMyWay() {
        return new DefaultKafkaConsumerFactory<>(new HashMap<>(), new StringDeserializer(), 
new ErrorHandlingDeserializer2<>(new JsonDeserializer<>(Foo.class)));
}

Using the latter setup for the ConsumerFactory, the ListenerConsumer fails to find the value.deserializer entry in the properties map and ends up setting the checkNullValueForExceptions field to false. Checking "if either the key or value contains a DeserializationException header" occurs only if checkNullValueForExceptions is set to true.

if (record.value() == null && this.checkNullValueForExceptions) {
   checkDeser(record, ErrorHandlingDeserializer2.VALUE_DESERIALIZER_EXCEPTION_HEADER);
}
if (record.key() == null && this.checkNullKeyForExceptions) {
   checkDeser(record, ErrorHandlingDeserializer2.KEY_DESERIALIZER_EXCEPTION_HEADER);
}

Can you explain what is the reason behind this?

[garyrussell]

Good catch - we don't check if the deserializer was configured manually.

As a work around, you should be able to set the property as well as constructing your own (which will take precedence over the property, but we'll still set the boolean based on the property).