WW-5724 Hand out a clone of the cached MessageFormat (6.x) - #1915
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WW-5724 Hand out a clone of the cached MessageFormat (6.x)#1915lukaszlenart wants to merge 1 commit into
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AbstractLocalizedTextProvider caches MessageFormat instances by pattern and locale and returned the cached instance itself from buildMessageFormat. MessageFormat is not thread-safe, so concurrent callers rendering the same message formatted through one shared instance; with a date or time sub-format that produced output for the wrong argument or an exception. buildMessageFormat now returns a clone of the cached instance, so the cached entry is only ever a template and is never formatted directly. MessageFormat.clone() deep-copies the sub-formats. The pattern-parsing cache is kept; measured against a fresh instance per call and against synchronizing on the shared instance, cloning is the cheapest of the three. Backport of the main change (#1914) to the 6.x line. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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September 11, 2026 13:49
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Fixes WW-5724
Backport of #1914 to the 6.x line.
AbstractLocalizedTextProvidercachesMessageFormatinstances by pattern and locale and returned the cached instance itself frombuildMessageFormat.MessageFormatis not thread-safe, so concurrent callers rendering the same message formatted through one shared instance; with a date or time sub-format that produced output for the wrong argument or an exception.buildMessageFormatnow returns a clone of the cached instance, so the cached entry is only ever a template and is never formatted directly.MessageFormat.clone()deep-copies the sub-formats on Java 8 as well (Calendar,DigitList,DateFormatSymbols). The pattern-parsing cache is kept.Two tests added to
StrutsLocalizedTextProviderTest, matching the main change: one asserts two lookups of the same pattern no longer return the same instance while the cache still holds one entry; the other renders a{0,date,short}message from four threads with distinct dates and asserts every output matches its own argument. Both failed before the change.No configuration or API change.
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