Udo Schnurpfeil created OWB-703:
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Summary: getBeans cache key algorithm must be unique
Key: OWB-703
URL: https://issues.apache.org/jira/browse/OWB-703
Project: OpenWebBeans
Issue Type: Bug
Affects Versions: 1.1.5, 1.1.4
Environment: OWB 1.1.4, Codi 1.0.5, MyFaces 2.0.13, Tobago 1.5.7
Reporter: Udo Schnurpfeil
Priority: Critical
Our application was tested in a Pre-Production environment, and it turns out a
problem which occurs sometime after 2 weeks but sometimes after a short time:
[9/11/12 10:46:27:288 CEST] 0000009e ServletWrappe E SRVE0068E: Uncaught
exception thrown in one of the service methods of the servlet:
FacesServlet. Exception thrown : java.lang.IllegalArgumentException: Given bean
type : class
org.apache.myfaces.extensions.cdi.jsf.impl.scope.conversation.ViewAccessConversationExpirationEvaluatorRegistry
is not applicable for the bean instance : BereitstellungModelLoaderImpl,
Name:BereitstellungModelLoader, WebBeans Type:MANAGED, API
Types:[java.lang.Object,de.nordlbit.iopc.optionen.jsf.model.BereitstellungModelLoader,de.nordlbit.iopc.optionen.jsf.model.BereitstellungModelLoaderImpl,java.io.Serializable],
Qualifiers:[javax.inject.Named,javax.enterprise.inject.Any,javax.enterprise.inject.Default]
at
org.apache.webbeans.container.BeanManagerImpl.getReference(BeanManagerImpl.java:923)
at
org.apache.webbeans.container.InjectableBeanManager.getReference(InjectableBeanManager.java:133)
at
org.apache.myfaces.extensions.cdi.core.impl.util.CodiUtils.getContextualReference(CodiUtils.java:215)
at
org.apache.myfaces.extensions.cdi.core.impl.util.CodiUtils.getContextualReferenceByClass(CodiUtils.java:179)
at
org.apache.myfaces.extensions.cdi.core.impl.util.CodiUtils.getContextualReferenceByClass(CodiUtils.java:139)
at
org.apache.myfaces.extensions.cdi.jsf.impl.util.ConversationUtils.postRenderCleanup(ConversationUtils.java:668)
at
org.apache.myfaces.extensions.cdi.jsf2.impl.listener.phase.CodiLifecycleWrapper.render(CodiLifecycleWrapper.java:128)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:191)
at
com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1213)
[...]
I think the reason is, that two objects got the same key in the map.
So we got wrong objects.
After this exception the application must be restarted, no request works
anymore.
How can this happen?
Problem number 1:
Looking in the implementation:
There will be computed a key of type Long from all given parameters.
Parameters: injectionPointType, bdaBeansXMLPath, qualifiers
In practice we have one "injectionPointType" (say t) and one "qualifiers" (say
q) and the computed hash code will be:
key = hash(t) + 29 * hash(q)
assume: hash(t)=1000 and hash(q)=100
we got a key of 1000 + 29 * 100 = 3900
but that's the same like
1029 + 29 * 99 = 3900
1058 + 29 * 98 = 3900
1087 + 29 * 97 = 3900
and so on.
If we got parameter with hash(t)=1029 and hash(q)=99 we have found 2 beans with
the same key.
With that our map is broken, because the 2nd bean will remove the 1st bean
while adding (with the same key).
Problem number 2:
Hash codes are generally not suitable to be used as keys because there are not
unique.
The JavaDoc of the Object.hashCode() method says:
"It is not required that if two objects are unequal according to the
equals(Object) method,
then calling the hashCode method on each of the two objects must produce
distinct integer results."
The strings "org.apache.kcmdjx" and "java.lang.Object" have the same hash code
(at least in my Apple java VM).
Solution:
I see 3 solutions here:
Solution 1:
Do the same like in 1.1.3: Build a String with all information inside.
Disadvantage: slow
Solution 2:
Create an helper object, which contains the unconverted information analog to
e.g.: org.apache.myfaces.tobago.internal.context.ClientPropertiesKey
This will be faster than string concatenation, but there is to create an object
as well.
Solution 3:
Using a map which can handle more than one key.
E. g. org.apache.commons.collections.map.MultiKeyMap
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