zifeihan commented on issue #6456:
URL: https://github.com/apache/skywalking/issues/6456#issuecomment-787394620
> I have one question about the following code:
>
> ```java
> public class CallbackConstructorInterceptor implements
InstanceConstructorInterceptor {
>
> @Override
> public void onConstruct(EnhancedInstance objInst, Object[]
allArguments) {
> Callback callback = (Callback) allArguments[0];
> CallbackCache cache;
> if (null != objInst.getSkyWalkingDynamicField()) {
> cache = (CallbackCache) objInst.getSkyWalkingDynamicField();
> } else {
> cache = new CallbackCache();
> }
> cache.setCallback(callback);
> objInst.setSkyWalkingDynamicField(cache);
> }
> }
> ```
>
> In `KafkaTemplateCallbackInstrumentation`,
`CallbackConstructorInterceptor` is registerred as constructor interceptor for
`org.apache.kafka.clients.producer.KafkaProducer$InterceptorCallback`. Since
`onConstruct` is called after `KafkaProducer$InterceptorCallback`'s origin
constructor invocation, I think that `objInst.getSkyWalkingDynamicField()`
always return `null`.
>
> Under what conditions `objInst.getSkyWalkingDynamicField()` is not `null`?
@yaojingguo Regarding this code, I agree with you. I think here,
objInst.getSkyWalkingDynamicField() is always null. Do you have an environment
to simulate it?
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