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https://issues.apache.org/jira/browse/WW-5690?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lukasz Lenart resolved WW-5690.
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Resolution: Fixed
> Defer loading the dev-mode error template until first use
> ---------------------------------------------------------
>
> Key: WW-5690
> URL: https://issues.apache.org/jira/browse/WW-5690
> Project: Struts 2
> Issue Type: Task
> Components: Core
> Reporter: Lukasz Lenart
> Assignee: Lukasz Lenart
> Priority: Major
> Fix For: 7.4.0
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> {{DefaultDispatcherErrorHandler.init()}} built a FreeMarker configuration and
> loaded {{/org/apache/struts2/dispatcher/error.ftl}} on *every* startup —
> including production, where the problem report is never rendered.
> {{handleError(...)}} only reaches it when devMode is on; otherwise it
> delegates to the container's error page via {{sendErrorResponse(...)}}.
> So every Struts application paid to initialise FreeMarker for a page most of
> them never show.
> h2. Change
> {{init(ServletContext)}} now only stores the servlet context. A new
> {{protected getTemplate()}} loads the template on first use and caches it in
> a {{volatile}} field.
> No lock: two threads racing on the very first error may both load it, which
> is harmless — FreeMarker caches templates in its own {{Configuration}} — and
> cheaper than locking a path taken once per application lifetime.
> h2. Behavioural change
> A missing or unparsable {{error.ftl}} used to throw {{StrutsException}} from
> {{init()}} and fail the application at boot. It now surfaces on the first
> dev-mode error, where the existing {{catch}} in {{handleErrorInDevMode(...)}}
> degrades to {{sendError(code, "Unable to show problem report: ...")}}. A
> dev-only template should not stop a production application starting.
> h2. Scope
> Startup cost only. The {{FreemarkerManager}} injection, the
> {{freemarker.template.Template}} import and {{error.ftl}} itself all remain —
> removing them is WW-5693.
> This ticket was originally filed as "Remove core's FreeMarker dependency from
> DefaultDispatcherErrorHandler" and has been narrowed to the change that
> actually shipped.
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