Federico Mariani created CAMEL-24100:
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Summary: camel-bean: class: endpoint creates a new bean instance
per message despite default Singleton scope
Key: CAMEL-24100
URL: https://issues.apache.org/jira/browse/CAMEL-24100
Project: Camel
Issue Type: Bug
Components: camel-bean
Affects Versions: 4.21.0
Reporter: Federico Mariani
A {{class:}} endpoint with the default {{scope=Singleton}} creates a *new bean
instance for every message*, contradicting both the documented Singleton scope
semantics ("the bean is created or looked up only once and reused for the
lifetime of the endpoint") and the class component docs ("works in the same way
as the Bean component").
*Cause*
{{ClassComponent.createEndpoint()}} pre-sets a {{ConstantTypeBeanHolder}} on
the endpoint. In {{BeanEndpoint.doInit()}} the singleton-caching branch
({{registryBean.createCacheHolder()}}) only runs when {{getBeanHolder() ==
null}} — so for {{class:}} endpoints it is skipped entirely and the scope
option is never honored. {{ConstantTypeBeanHolder.getBean()}} then runs on
*every exchange*: a registry {{findSingleByType}} type-scan plus
{{Injector.newInstance(type)}}.
*Consequences*
# Stateful beans silently lose state between messages.
# Per-message reflection/instantiation + registry type-scan overhead.
# Inverse inconsistency: when {{bean.xxx}} options are present,
{{ClassComponent}} builds a {{ConstantBeanHolder}} (one shared instance) — so
{{class:Foo?scope=Prototype&bean.x=1}} silently behaves as *singleton* while
{{class:Foo?scope=Singleton}} behaves as *prototype*.
*Suggested fix*
In {{BeanEndpoint.doInit()}}, when the pre-set holder is a
{{ConstantTypeBeanHolder}} and scope is Singleton, call
{{holder.createCacheHolder()}}; or make {{ClassComponent}} scope-aware when
choosing the holder type.
*Reproducer*
Attached test {{ClassComponentSingletonScopeTest}} fails on main
(4.22.0-SNAPSHOT): 2 messages create 2 instances.
{noformat}
org.opentest4j.AssertionFailedError: Singleton scope should create the bean
only once ==> expected: <1> but was: <2>
{noformat}
_This issue was found by an AI-assisted code review. Reported by Claude Code on
behalf of [~fmariani] (GitHub: Croway)._
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