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https://issues.apache.org/jira/browse/ARIES-1554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15300545#comment-15300545
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Witek commented on ARIES-1554:
------------------------------
The consequence of using {{instanceof}} instead of {{getClass() ==
o.getClass()}} is that if someone extends FelixResourceAdapter (for whichever
reason), then:
a) she needs to overwrite the equals method to properly return true for objects
of superclass as the {{equals}} method needs to be symmetric (See
[documentation|https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#equals%28java.lang.Object%29]
and this [stackoverflow post|http://stackoverflow.com/a/32223])
b) the subtypes will always be equal (for maps, sets,...) as long as _type_,
_symbolicName_ and _version_ are the same
On the other hand, if we use {{getClass() == o.getClass()}} then subtypes will
always be different (not equal).
Is the approach that uses {{instanceof}} preferred here?
> FelixResourceAdapter returns true for resources of other types
> --------------------------------------------------------------
>
> Key: ARIES-1554
> URL: https://issues.apache.org/jira/browse/ARIES-1554
> Project: Aries
> Issue Type: Bug
> Components: Subsystem
> Environment: All
> Reporter: Thomas Watson
> Assignee: Thomas Watson
>
> The Resource implementation
> org.apache.aries.subsystem.util.felix.FelixResourceAdapter does an equality
> check based on the osgi.identity name, version, and type. This typically is
> not an issue but the contract for Resource.equals states the following:
> <javadoc>
> This Resource is equal to another Resource if both have the same content and
> come from the same location. Location may be defined as the bundle location
> if the resource is an installed bundle or the repository location if the
> resource is in a repository.
> </javadoc>
> The assumption is that if the osgi.identity name, version and type are equal
> then the resources have the "same content". But the implementation does not
> take into account the location. This causes issues if resources are used as
> keys in a Map and the Map will contain resources of different implementation
> types. This is done by the felix resolver implementation. In some scenarios
> the subsystems will return to the resolver resources from the OBR repository
> and from the system repository (installed bundles) that have the same name,
> version, type. From the resolver's perspective these two resources must be
> treated as distinctly different resources because they come from completely
> different locations. And the framework's Resource implementation of equals
> does return false if checked against a FelixResourceAdapter, but the
> FelixResourceAdapter equals method will return true if check against the
> framework's Resource implementation. This inconsistency in the equals
> behavior reeks havoc for Map implementations. Usually the issue is very
> intermittent because of they way hash slots are determined based on
> hashcodes, but in rare cases these two resources will be slotted the same and
> collide with eachother depending on the Map implementation.
> At a minimum the FelixResourceAdapter should check that the other object is
> an instance of FelixResourceAdapter to be able to return true. This makes
> the simple assumption that if the Resource is not of type
> FelixResourceAdapter then there is no way the resource is at the same
> location.
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