[jbosscache-issues] [JBoss JIRA] Created: (JBCACHE-1412) TreeCacheMarshaller140 marshalling replaces distinct but equal() objects

[Brian Stansberry (JIRA)]

TreeCacheMarshaller140 marshalling replaces distinct but equal() objects
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                 Key: JBCACHE-1412
                 URL: https://jira.jboss.org/jira/browse/JBCACHE-1412
             Project: JBoss Cache
          Issue Type: Bug
      Security Level: Public (Everyone can see)
          Components: Replication
    Affects Versions: 1.4.1.SP9
            Reporter: Brian Stansberry
            Assignee: Manik Surtani
            Priority: Critical


The marshalling logic in TreeCacheMarshaller140 uses a HashMap as store of objects already written so it can replace subsequent writes of the same object with a magic number. Use of a HashMap is incorrect, as magic number replacement should only occur if an object with the same identity is detected, not one that just satisfies equals() but not ==.

Either a custom map that uses System.identityHashCode() for hashing and == instead of equals() for equality is needed, or the map key should be System.identityHashCode(). Note the Object.hashCode() javadocs do not absolutely guarantee uniqueness in System.identityHashCode(), so a custom map is probably better:

"As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)"

Non-uniquenesss in System.identityHashCode() might be more of an issue in systems with large heaps that can't be addressed with 32 bits.

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