[jira] [Commented] (BEANUTILS-402) Double-Checked Locking anti pattern in WeakFastHashMap

["Hans-Peter Störr (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEANUTILS-402?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15449094#comment-15449094 ] 

Hans-Peter Störr commented on BEANUTILS-402:
--------------------------------------------

Why don't you just fix it with making org.apache.commons.beanutils.WeakFastHashMap.map volatile? That's easy and solves the problem. I guess hardly anyone uses Java versions less than Java 5.

> 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
>             Fix For: 2.0
>
>
> 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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