Ramu kakarla created CAMEL-24305:
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Summary: KafkaComponent does not autowire custom
KafkaClientFactory because default instance is created before autowiring
Key: CAMEL-24305
URL: https://issues.apache.org/jira/browse/CAMEL-24305
Project: Camel
Issue Type: Bug
Components: camel-kafka
Affects Versions: 4.21.0
Environment:
Apache Camel 4.18.x (observed in Red Hat build 4.18.1.redhat-00019)
Spring Boot
camel-kafka-starter
Reporter: Ramu kakarla
The Kafka component documentation marks the kafkaClientFactory component option
as autowired. However, when a custom KafkaClientFactory is registered as a
Spring bean, it is not injected into the KafkaComponent.
Instead, the component creates a default KafkaClientFactory during
initialization before the autowiring phase executes. Since the field is already
non-null, Camel's autowiring logic skips it.
Expected behavior
When a single KafkaClientFactory bean is available in the registry, it should
be autowired into KafkaComponent as documented.
Actual behavior
KafkaComponent.doInit() creates a default KafkaClientFactory before
LifecycleStrategySupport.doAutoWire() runs.
The execution order is:
KafkaComponent is instantiated.
ComponentCustomizers execute.
KafkaComponent.doInit() creates the default KafkaClientFactory.
LifecycleStrategySupport.doAutoWire() executes.
doAutoWire() skips kafkaClientFactory because the field is already populated.
As a result, the custom KafkaClientFactory bean is never injected.
Steps to reproduce
Create a Spring Boot application using camel-kafka-starter.
Define a custom implementation of KafkaClientFactory as a Spring bean.
Use a Kafka endpoint so that KafkaComponent is initialized.
Observe that the custom bean is not injected into KafkaComponent.
Workaround
Register a ComponentCustomizer that sets the KafkaClientFactory before
KafkaComponent.doInit() executes. This avoids creation of the default instance
and allows the custom implementation to be used.
A minimal workaround implementation is attached.
Additional information
The attached stack trace shows the initialization sequence demonstrating that
KafkaComponent.doInit() executes before LifecycleStrategySupport.doAutoWire().
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