Double-Checked Locking anti pattern in WeakFastHashMap
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Key: BEANUTILS-402
URL: https://issues.apache.org/jira/browse/BEANUTILS-402
Project: Commons BeanUtils
Issue Type: Bug
Components: Bean / Property Utils, ConvertUtils & Converters, Locale
BeanUtils / Converters
Affects Versions: 1.8.3
Environment: Win XP, but doesn't matter
Reporter: Volker Malzahn
The implementation of WeakFastHashMap has the flaw of implementing the
Double-Checked Locking anti pattern (see JavaDoc of that class). As described
in the JavaDoc "This class is not cross-platform.". In
https://issues.apache.org/jira/browse/BEANUTILS-318 and
https://issues.apache.org/jira/browse/BEANUTILS-373 this was solved for
MethodUtils (usage of WeakFastHashMap). But following classes still use
WeakFastHashMap for a cache: BeanUtils, ConvertUtilsBean, PropertyUtilsBean,
LocaleConvertUtilsBean.
I would suggest to make WeakFastHashMap deprecated and to change every usage of
that class inside the commons-beanutils classes to a synchronized normal
WeakHashMap like done (as the second step) in
https://issues.apache.org/jira/browse/BEANUTILS-318. Otherwise strange things
may happen in unusual plattforms/environments. An alternative could be to use
"volatile" inside WeakFastHashMap which would fix it for Java 5 and higher (see
http://en.wikipedia.org/wiki/Double-checked_locking or
http://www.cs.umd.edu/~pugh/java/memoryModel/jsr-133-faq.html#volatile).
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