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  1. Log4j 2
  2. LOG4J2-891

AbstractLifecycle should not implement equals() and hashCode()

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 2.1
    • Fix Version/s: 2.2
    • Component/s: API
    • Labels:
      None

      Description

      Starting with version 2.1, the AbstractLifeCycle class (which I think was also introduced in that version) have an implementation of equals() and hashCode() which is being inherited by other core classes such as LoggerContext. That implementation considers two objects as equals if they have the same LifeCycle.State, and calculates the hashCode based on that same attribute.

      This has unwanted side effects:

      • For a class like LoggerContext, that implementation of equals() doesn't apply at all. For example, I'm using log4j2 as the logging technology for an application container. Each deployed application get its own LoggerContext. Those LoggerContext are not equal just because they have the same status.
      • AbstractLifeCycle instances are no longer suitable for use in a HashSet or HashMap. Because every instance with the same state will return the same hashCode, changes are that many of them will end up in the same bucket. Also, because of the same reasons which make the equals() implementation wrong, invokations to HashSet#contains(AbstractLifeCycle) might start showing unexpected behavior.

      This was fine in 2.0.2 and I have verified these issues with the LoggerContext class. I'm pretty sure that the same thing happens to all its subclasses. I don't think that the state is a good attribute to determine equality or idempotency.

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              • Assignee:
                Unassigned
                Reporter:
                mgonzalez Mariano Gonzalez
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