[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-3362) Detect cyclic dependencies and throw exception
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https://jira.jboss.org/jira/browse/JBSEAM-3362?page=com.atlassian.jira.pl...
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Matt Drees commented on JBSEAM-3362:
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1) I'll take a look
2) Correct me if I'm wrong here. My understanding of what you'd like is this:
Say Foo has an @In(required=false) attribute called somethingProvidedByBar. When
someMethod() is invoked on Foo, and trying to satisfy the injection of bar results in Bar
calling Foo.someOtherMethod(), then we should bail on this injection attempt, and let
somethingProvidedByBar be null for the invocation of someMethod().
I see the desirability of this, but I don't know how to do the "bail" part.
A cycle is only detected when someOtherMethod() is called, and so trying to bail would
probably require throwing a special exception to propagate back down to the initial
injecting of Foo, where we'd catch it and go on to the next attribute to inject. But
throwing exceptions seems like a bad idea, especially when they might inadvertently cause
a transaction rollback.
Let me know what you think.
Detect cyclic dependencies and throw exception
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Key: JBSEAM-3362
URL: https://jira.jboss.org/jira/browse/JBSEAM-3362
Project: Seam
Issue Type: Feature Request
Components: Core
Affects Versions: 2.0.3.CR1, 2.1.0.BETA1
Reporter: Matt Drees
Assignee: Matt Drees
Priority: Minor
Fix For: 2.0.3.CR2, 2.1.0.CR1
Imagine a scenario like this. Some client calls someMethod() on a component called Foo.
BijectionInterceptor tries to inject Foo's @in attributes, one of which requires
calling a factory method on Bar. Bar's factory method in turn calls
Foo.someOtherMethod(). Foo is not in a state where it can support method calls, because
it is in the process of injecting dependencies, so this sort of cyclic dependency should
not be allowed. Seam should throw an exception in this case.
BijectionInterceptor used to be coded such that someOtherMethod() would run without any
complaints, and any @In attributes may or may not be null, depending on which fields were
injected first. Recent changes to BijectionInterceptor (for JBSEAM-3295) have changed
this behavior, and now an finite loop results. Neither of these behaviors is desirable.
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