[GitHub] [kafka] RivenSun2 commented on a diff in pull request #12010: KAFKA-13793: Add validators for configs that lack validators

[GitBox <gi...@apache.org>]

RivenSun2 commented on code in PR #12010:
URL: https://github.com/apache/kafka/pull/12010#discussion_r864331037


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clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerConfig.java:
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@@ -601,11 +607,16 @@ private void maybeOverrideClientId(Map<String, Object> configs) {
     protected static Map<String, Object> appendDeserializerToConfig(Map<String, Object> configs,
                                                                     Deserializer<?> keyDeserializer,
                                                                     Deserializer<?> valueDeserializer) {
+        // validate deserializer configuration, if the passed deserializer instance is null, the user must explicitly set a valid deserializer configuration value

Review Comment:
   The situation you describe should be that the key.deserializer parameter is not set.
   
   The changes here are to deal with two situations:
   1. As described in JIRA, when the user explicitly sets null, expect a `ConfigException` instead of a `NullPointerException`. `props.put("key.serializer", null);`
   
   2. In order to be compatible with the usage scenarios of some users, as @C0urante  mentioned, the user will only pass in the serializer instance when building the KafkaProducer:
   
   > I'm wondering if people might be constructing ProducerConfig and ConsumerConfig instances in order to do some kind of validation before storing a configuration somewhere, that's then used later to create a producer/consumer. If so, they might be omitting the (de)serializer properties (or rather, just using null as a placeholder) if the (de)serializer isn't known at that time and they plan on using the constructor that accepts already-instantiated Serializer/Deserializer instances.



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