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https://issues.apache.org/jira/browse/LANG-739?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13803035#comment-13803035
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Philippe Renon commented on LANG-739:
-------------------------------------
Hi Woosan Ko,
The registry in question is located in the ToStringStyle class (in version 2.3).
If an object's hash code changes after it is added to that registry, then
removal will not happen and the object will be leaked (i.e. kept forever in the
registry).
I checked the latest code and the situation is somewhat better because the
registry uses a WeakHashMap which will prevent the leak. So now if the hash
code of a "registered" object changes and is not removed from the registry, the
registry will not prevent it from being removed.
Regards,
Philippe.
> ToStringBuilder leaks memory if toString method causes hash code to be changed
> ------------------------------------------------------------------------------
>
> Key: LANG-739
> URL: https://issues.apache.org/jira/browse/LANG-739
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.builder.*
> Affects Versions: 2.3
> Reporter: Philippe Renon
> Fix For: Patch Needed
>
>
> We have the following abstract class:
> {code}
> public class AbstractMessageItem {
> private String toString;
> public boolean equals(final Object obj) {
> return EqualsBuilder.reflectionEquals(this, obj);
> }
> public int hashCode() {
> return HashCodeBuilder.reflectionHashCode(this);
> }
> public String toString() {
> if (toString == null) {
> toString = ToStringBuilder.reflectionToString(this);
> }
> return toString;
> }
> }
> {code}
> We also have two concrete classes extending the above class and one of them
> has a reference to the other.
> Now, if we call toString() on the 1st one, this will in turn call toString()
> on the second one.
> The call to toString() on the second one will cause its hash code to be
> changed and as a consequence will also change the hashCode of the first one
> *while* computing its toString().
> This causes the _infinite loop avoidance_ mechanism (i.e. the registry) to
> fail to unregister some objects and memory will be leaked.
> I believe that this leak can be avoided by using the system identity hash
> code when registering objects (as is done in HashCodeBuilder) instead of the
> user hash code.
> I know the issue can be worked around by removing the toString field (and
> loosing a dubious "performance enhancement" hack) or by making it transient,
> but I think that other "mutating" toString() methods can happen in the field
> (sometimes for good reasons) and fixing ToStringBuilder can be of help in
> some cases.
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