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https://issues.apache.org/jira/browse/LANG-349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12521542
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David I. commented on LANG-349:
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It does make sense that the reflection code isn't synchronized (since
toString() isn't?). That might be the core issue.
It helps to know that you aren't using a HashMap internally.
I could wrap the builder code in a synchronized block to prevent this. Does
that sound like a good solution? If so, it would be nice to update the
documentation to point out how toString and the reflection code isn't thread
safe.
Would it be possible to have add a "thread-safe" version that synchronizes on
each variable (or the whole class) before reading it during the reflection
process?
> Deadlock using ReflectionToStringBuilder
> ----------------------------------------
>
> Key: LANG-349
> URL: https://issues.apache.org/jira/browse/LANG-349
> Project: Commons Lang
> Issue Type: Bug
> Affects Versions: 2.0
> Environment: java version "1.5.0_10"
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_10-b03)
> Java HotSpot(TM) Server VM (build 1.5.0_10-b03, mixed mode)
> >uname -a
> Linux fwjsfimat04 2.4.21-32.EL #1 SMP Fri Apr 15 21:02:58 EDT 2005 x86_64
> x86_64 x86_64 GNU/Linux
> Reporter: David I.
> Priority: Critical
> Fix For: 2.4
>
>
> I used the ReflectionToStringBuilder on an object to output debugging
> messages to Log4j. If this object was picked up by two different threads and
> the toString() method was called at the same time in two different threads, a
> deadlock occurrs.
> Here is a stack trace from using jstack:
> Thread 1172: (state = BLOCKED)
> - java.util.Vector.hashCode() @bci=0, line=938 (Interpreted frame)
> - java.util.HashMap.containsKey(java.lang.Object) @bci=6, line=377 (Compiled
> frame)
> - org.apache.commons.lang.builder.ReflectionToStringBuilder.toString()
> @bci=50, line=522 (Compiled frame)
> -
> org.apache.commons.lang.builder.ReflectionToStringBuilder.toString(java.lang.Object,
> org.apache.commons.lang.builder.ToStringStyle, boolean, java.lang.Class)
> @bci=12, line=265 (Interpreted frame)
> -
> org.apache.commons.lang.builder.ReflectionToStringBuilder.toString(java.lang.Object,
> org.apache.commons.lang.builder.ToStringStyle) @bci=4, line=197 (Interpreted
> frame)
> -
> org.apache.commons.lang.builder.ToStringBuilder.reflectionToString(java.lang.Object,
> org.apache.commons.lang.builder.ToStringStyle) @bci=2, line=170 (Interpreted
> frame)
> [...]
> Thread 1191: (state = BLOCKED)
> - java.util.Vector.hashCode() @bci=0, line=938 (Interpreted frame)
> - java.util.HashMap.containsKey(java.lang.Object) @bci=6, line=377 (Compiled
> frame)
> - org.apache.commons.lang.builder.ReflectionToStringBuilder.toString()
> @bci=50, line=522 (Compiled frame)
> [...]
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