[#LANG-334] Enum is not thread-safe

Commons Lang

Enum is not thread-safe

Created: 14/May/07 10:30 PM Updated: 05/Sep/07 10:14 AM

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Component/s:

None

Affects Version/s:

None

Fix Version/s:

2.4

Time Tracking:

Not Specified

File Attachments:

File Name	Date Attached	Attached By	Size
334.patch	2007-07-28 04:14 AM	Jason Madden	2 kB
EnumPlay.java	2007-06-06 03:24 PM	Henri Yandell	1 kB

Resolution Date:

05/Sep/07 10:14 AM

Description

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Enum uses no synchronization. Even if you assume that instances are only declared statically, the cEnumClasses map is global and can be written to when a thread triggers static initialization of B.class while some other thread is doing getEnumList(A.class). Unsynchronized access of a map undergoing mutation is not thread-safe.

This isn't theoretical. We're seeing ValuedEnum.getEnum(X.class, 0) return null after returning the correct value over 100,000 times, and then return the correct value again on the next invocation.

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Repository	Revision	Date	User	Message
ASF	#572930	Wed Sep 05 10:13:49 UTC 2007	bayard	Applying Jason Madden's patch from ~~LANG-334~~ to provide enums.Enum with optimized thread safety. As Jason's used this in production I think it's fair to use it rather than the simpler Collections.synchronizedMap(..). I've also applied the patch to the enum.Enum
				Files Changed
				MODIFY /commons/proper/lang/trunk/src/java/org/apache/commons/lang/enum/Enum.java MODIFY /commons/proper/lang/trunk/src/java/org/apache/commons/lang/enums/Enum.java