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https://issues.apache.org/jira/browse/WW-5827?focusedWorklogId=1052409&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-1052409
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ASF GitHub Bot logged work on WW-5827:
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Author: ASF GitHub Bot
Created on: 04/Nov/26 11:21
Start Date: 04/Nov/26 11:21
Worklog Time Spent: 10m
Work Description: lukaszlenart commented on PR #2084:
URL: https://github.com/apache/struts/pull/2084#issuecomment-6629291713
Thanks for the cleanup, and sorry for the slow answer on the scope question.
Yes, please fold both into this PR. You're right about the logging: with
failed lookups no longer cached, the ERROR plus stack trace from the
`StrutsPreparerFactory` fallback would repeat on every request instead of
appearing once, so it belongs with this change. I've added a third section to
[WW-5827](https://issues.apache.org/jira/browse/WW-5827) covering
`StrutsPreparerFactory`: check the type before building the bean, construct at
most once, and don't log a full ERROR stack trace per request for a failed
lookup.
One small thing from the last push: `BasicPreparerFactory.getPreparer` now
has trailing whitespace after `if (preparer == null) {` and on the blank line
before `putIfAbsent`.
Issue Time Tracking
-------------------
Worklog Id: (was: 1052409)
Time Spent: 50m (was: 40m)
> Tiles plugin: check the preparer type before instantiating it and do not
> cache failed preparer lookups
> ------------------------------------------------------------------------------------------------------
>
> Key: WW-5827
> URL: https://issues.apache.org/jira/browse/WW-5827
> Project: Struts 2
> Issue Type: Improvement
> Components: Plugin - Tiles
> Reporter: Lukasz Lenart
> Priority: Major
> Time Spent: 50m
> Remaining Estimate: 0h
>
> Three issues in how the Tiles plugin resolves view preparers.
> *ClassUtil instantiates before checking the type*
> {{ClassUtil.getClass(String, Class)}} loads the class with
> {{Class.forName(className, true, classLoader)}}, so static initialisation
> runs on lookup. {{ClassUtil.instantiate(String, boolean)}} passes
> {{Object.class}} as the base type and calls {{newInstance()}}; the
> {{ViewPreparer}} check happens only afterwards, as a cast in
> {{BasicPreparerFactory.createPreparer}}. A configured preparer name that is
> not a {{ViewPreparer}} is therefore loaded, initialised and constructed
> before it is rejected.
> Expected: resolve the class without initialising it, apply the expected base
> type ({{ViewPreparer}}) before instantiation, and fail without constructing
> anything when it does not match.
> *BasicPreparerFactory caches failed lookups in a non-thread-safe map*
> {{BasicPreparerFactory.getPreparer}} stores the result of {{createPreparer}}
> in a plain {{HashMap}}, including the {{null}} returned when the class cannot
> be found. A failed lookup stays cached for the lifetime of the factory, and
> the map is read and written concurrently by request threads.
> Expected: do not cache failed lookups, and use a thread-safe map (e.g.
> {{ConcurrentHashMap}}).
> *StrutsPreparerFactory constructs before checking the type, twice on failure,
> and logs every failure at ERROR*
> {{StrutsPreparerFactory.createPreparer}} builds the preparer through
> {{ObjectFactory.buildBean}} and casts to {{ViewPreparer}} afterwards, so the
> type check above is not applied on this path. When the cast fails, the
> {{catch (Exception)}} falls back to {{super.createPreparer}}, which
> constructs the class a second time. The fallback logs at ERROR with a full
> stack trace; once failed lookups are no longer cached, a misconfigured
> preparer name would log that on every request instead of once.
> Expected: check the type before building the bean, construct at most once,
> and keep a failed lookup from producing a full ERROR stack trace per request.
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