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From "Volker Malzahn (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (BEANUTILS-402) Double-Checked Locking anti pattern in WeakFastHashMap
Date Wed, 26 Oct 2011 13:33:33 GMT
Double-Checked Locking anti pattern in WeakFastHashMap
------------------------------------------------------

                 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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