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Posted to dev@sling.apache.org by "Lukas Eder (JIRA)" <ji...@apache.org> on 2013/03/13 10:04:12 UTC
[jira] [Updated] (SLING-2786) ResourceMetadata contains stale
unmodifiableMap cache after clone()
[ https://issues.apache.org/jira/browse/SLING-2786?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Lukas Eder updated SLING-2786:
------------------------------
Attachment: ResourceMetadataTest.java.patch
> ResourceMetadata contains stale unmodifiableMap cache after clone()
> -------------------------------------------------------------------
>
> Key: SLING-2786
> URL: https://issues.apache.org/jira/browse/SLING-2786
> Project: Sling
> Issue Type: Bug
> Components: API
> Affects Versions: API 2.3.0
> Reporter: Lukas Eder
> Priority: Minor
> Attachments: ResourceMetadataTest.java.patch
>
>
> Super types of ResourceMetadata (java.util.HashMap and java.util.AbstractMap) correctly implement caching for members such as entrySet, keySet, values, etc. Two things should be considered:
> 1. The cache should be marked transient. It is not desireable to serialise / deserialise the "unmodifiableMap" cache. Only the isReadOnly flag should be serialised
> 2. clone() should be overridden in order to reset the cache on cloned instances
> Consider the following code:
> ResourceMetadata map1 = new ResourceMetadata();
> map1.put("key1", "value1");
> map1.lock();
> map1.values(); // Enforce the creation of the cache
> ResourceMetadata map2 = (ResourceMetadata) map1.clone();
> Now, map2 contains an unmodifiable wrapper of map1. While this generally behaves correctly, there are two problems:
> a) This is a potential memory leak as clones hold a reference to the original map.
> b) If unlock() is ever added, this might lead to a subtle bug when (after the above code):
> - map1.unlock() is called
> - map1 is modified
> - map2 will reflect map1's modifications, even if map2 should still be locked
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