[BEANUTILS-402] Double-Checked Locking anti pattern in WeakFastHashMap

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.8.3
• Fix Version/s: 2.0.0
• Component/s: Bean / Property Utils, ConvertUtils & Converters, Locale BeanUtils / Converters

Environment

Win XP, but doesn't matter

• Assignee: Unassigned
• Reporter: Volker Malzahn
• Created: 26/Oct/11 13:33
• Updated: 23/Oct/19 17:44
• Resolved: 23/Oct/19 17:44

Description

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).

Issue Links

• links to: GitHub Pull Request #15