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Skip the _method read for multipart requests over the size limit - #16186

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Skip the _method read for multipart requests over the size limit#16186
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Stacked on #16152. GitHub will show this against 8.0.x with #16152's (and #16149's)
commits included until that merges, at which point this rebases to just its own commit.

HiddenHttpMethodFilter.getHttpMethodOverride reads _method on every POST, including
multipart ones, which makes the container parse the request body. #16152 makes that read
tolerant of a parse failure, so an oversized upload no longer aborts the filter chain - but
the read, and the parse it triggers, is still attempted every time, even for a request
already declared (via Content-Length) larger than the configured
grails.controllers.upload.maxRequestSize.

This adds a size check ahead of the read: when Content-Length is known and already over
the configured limit, skip straight to the X-HTTP-Method-Override header fallback instead
of attempting a read that's going to fail anyway. Anything the check can't rule out up front

  • chunked transfer-encoding, no Content-Length - still goes through the existing tolerant
    read from Let oversized uploads reach the application's error handling #16152, so that safety net is unchanged. This only avoids the doomed attempt for
    the common case: a standard browser multipart form submission always declares
    Content-Length up front, which is what <g:uploadForm method="PUT"> produces.

Notes

  • Legitimate uploads under the configured limit still take the existing eager read - this
    doesn't remove the read, only skips it for requests already known to exceed the limit.
  • A client that omits Content-Length (chunked encoding) gets no benefit from the guard,
    but is no worse off than today: the tolerant read still applies.
  • <g:uploadForm method="PUT"> keeps working; there's a test for it with the guard
    configured and a within-limit body.

Verified

  • HiddenHttpMethodFilterTests: a mock request whose getParameter() throws (mirroring
    what the container does on a real parse failure) reaches "POST" without the read ever
    happening for an over-limit Content-Length; a within-limit multipart request with the
    guard configured still honours _method.
  • grails-test-examples-app1's FileUploadSpec against a real embedded Tomcat: the
    oversized-upload and method-override-on-multipart cases both pass unchanged.
  • :grails-controllers:test passes.

The request Grails exposed to controllers, tag libraries and GSPs was replaced
with the resolved MultipartHttpServletRequest for file uploads. That discarded
every request wrapper contributed after multipart resolution - the hidden HTTP
method filter, Spring Security, and any application filter - and required a
mutable pointer on GrailsWebRequest plus propagation code to maintain it.

The request is now always the outermost request, and multipart capabilities are
discovered from its wrapper chain via WebUtils.resolveMultipartRequest. When the
DispatcherServlet resolves a request Grails had already bound, the wrapper sits
above that request and cannot be reached by unwrapping, so it is also published
as a request attribute.

- Add WebUtils.resolveMultipartRequest and isMultipartContentType
- Add the MultipartRequest read surface to HttpServletRequestExtension so
  request.getFile(..) and friends keep working, failing loudly rather than
  returning null when the request is not a resolved multipart request
- Populate GrailsParameterMap through discovery rather than an instanceof check
- Replace GrailsWebRequest.setMultipartRequest and the multipart branch in
  getCurrentRequest with multipartRequestResolved, which only invalidates the
  cached params (apachegh-13837)
- Return the processed request from GrailsDispatcherServlet.checkMultipart, so
  the dispatch runs against it as Spring MVC expects
- Delete the unreachable multipart resolution in DefaultUrlMappingInfo, along
  with the undocumented grails.web.disable.multipart setting
- Make the SpringSecurityUtils multipart branch functional again; it read an
  attribute only the deleted DefaultUrlMappingInfo code ever wrote

request instanceof MultipartHttpServletRequest and casts to that type no longer
work; documented in the 8.0 upgrade guide.
isMultipartContentType had no production caller - only the test written for it.
Condense the six per-method javadoc blocks on the file upload accessors into one.
…ntext

GrailsWebRequest built a GrailsApplicationAttributes on every request, through a
reflective Constructor.newInstance. That object holds no request state - it caches
the beans its own comment calls "used very often" (template engine, GrailsApplication,
GroovyPagesUriService, MessageSource, plugin manager) - so building one per request
paid for the reflection and then discarded all five caches immediately.

It is now created on first use and cached in the servlet context, and rebuilt only
if the ApplicationContext it resolved against is no longer current, so a replaced or
restarted context (as happens between tests) is never served a stale instance. Its
lazily populated fields become volatile now that one instance is shared across
request threads.

Also stop allocating a UrlPathHelper per request or per call. Spring exposes
UrlPathHelper.defaultInstance and none of the four Grails instances were configured,
so they can share it.
…ceptors

UrlMappingsHandlerMapping.getHandlerExecutionChain re-implemented the loop from
AbstractHandlerMapping, so Grails-mapped requests silently missed whatever Spring
added to that method later. Currently that is the API version deprecation
interceptor, which means the Deprecation, Sunset and Link headers configured by
spring.mvc.apiversion.* were never emitted for a Grails-mapped request.

It now calls super and inserts the WebRequestInterceptors at the front, which
keeps the "OSIV must run first" ordering that motivated the override. The two
Grails interceptors are stateless, so they become shared instances instead of two
allocations per request, and the @CompileDynamic MappedInterceptor cast helper
goes away with the copied loop.

Also:
- Keep UrlMappingsHandlerMapping's own UrlPathHelper. UrlPathHelper.defaultInstance
  is read-only and that field is protected, so pointing it at the shared instance
  would break any subclass configuring it. It is a singleton bean, so there was no
  per-request allocation to save there anyway.
- Restore the previous LocaleContext in GrailsWebRequestFilter rather than clearing
  it, so a LocaleContext set by a filter outside Grails survives, matching Spring's
  own RequestContextFilter.
GrailsParameterMap's constructor defensively copied request.getParameterMap() into
a LinkedHashMap before walking it. updateNestedKeys only ever reads that map -
every put it makes goes into wrappedMap or a nested map it created - so the copy
was only ever needed to merge uploaded files in.

The servlet map (immutable per the servlet contract) is now walked directly, and
copied only when there are multipart files to merge, removing a map allocation and
a full entry copy per request for every non-upload request.
A URL mapping cache miss was the most expensive thing in the request path by three
orders of magnitude - 1964 ns for a URI only the default mapping serves, against
2.5 ns for a cache hit - because every miss ran a linear scan allocating a Matcher
for each of the ~56 compiled patterns in a mid-size application.

RegexUrlMapping now records each pattern's slash count at parse time and skips
patterns whose segment count rules them out. Every construct convertToRegex emits
is bounded to a single path segment except ".*", which comes only from a "**"
token, so a pattern without "**" can only match a URI with exactly its slash count
or one more, the extra one coming from the trailing "/??" every pattern ends with.
Patterns containing "**" are never skipped.

Candidates are skipped, never reordered, so the scan still returns the first
mapping that matches and declaration precedence is unchanged.

This replaces the patternByTokenCount map, which built exactly this index and was
never read by anything.

The holder computes the URI's slash count once per request rather than once per
mapping, and hoists the per-candidate LOG.isDebugEnabled() call out of the three
scan loops.
The adapter passed its callback to observe() as `{ -> i.before() } as BooleanSupplier`.
Groovy evaluates that coercion before entering observe(), so it ran even when the
ObservationRegistry is a no-op, and DefaultGroovyMethods.asType routes it through
CachedSAMClass.coerceToSAM to Proxy.newProxyInstance. Every matched interceptor
therefore cost a Closure, a Class[], a ConvertedClosure and a JDK dynamic proxy per
phase per request, with each callback dispatching reflectively through
ConversionHandler rather than calling the interceptor directly.

The phase is now a private enum that dispatches straight to before()/after(), so the
default path is a field read, a no-op check and an interface call. In the compiled
class groovy.lang.Reference references drop from 15 to 0 and the two closure classes
are gone. The observing path is structurally unchanged.

Also caches the logical interceptor name per class rather than recomputing it per
interceptor per phase per request, and reverses the matched-interceptor list in place
rather than copying it - the reversed list is stored back under the request attribute
and read by afterCompletion, so the ordering remains observable and unchanged.

Adds coverage for the observation path, which previously had none, including the
null-registry branch, the no-op registry branch, and error recording.
The controller AST transformer emitted the ALLOWED_METHODS_HANDLED request-attribute
guard twice into the same generated wrapper - once from convertToMethodAction and
again from wrapMethodBodyWithExceptionHandling - producing two byte-identical blocks
where the second could never do anything, because the first had already set the
attribute. It also emitted the guard, and its finally-block cleanup, for controllers
that declare no allowedMethods at all.

An action on a controller with no allowedMethods was paying four dynamic request
property gets, two getAttribute, a setAttribute, a removeAttribute and a compareEqual
per request for a guard that could never fire. Each request property get goes through
an indy callsite and RequestContextHolder, so this was not free.

The duplicate emission is removed, and the bookkeeping is now generated only for
controllers that declare a non-empty allowedMethods map. Gating it per action rather
than per controller looks equivalent but is not: the marker means "an action has
already begun handling this request" (apachegh-11444), so an unrestricted action must still
set it, or a restricted action it invokes programmatically starts rejecting the
request. Controllers that use allowedMethods generate byte-identical code to before.

Adds coverage for the command-object path, which had none.
…okup

Binding a command object resolved the DataBindingSourceRegistry, the MimeTypeResolver
and the GrailsWebDataBinder from the bean factory on every request, each with a
containsBean followed by a getBean, and did so twice because bindObjectToInstance
runs createDataBindingSource again. Holders.findApplication() is itself a getBean
rather than a field read, and was called twice more per bind.

These now resolve once per ApplicationContext, held in a single-entry volatile cache.
A map keyed by ApplicationContext would retain every context ever seen, since the
cached beans reference the context, so a single entry replaced whenever a different
context appears is both cheaper and the correct invalidation signal for dev restarts
and test contexts.

Separately, getBindingIncludeList used getDeclaredField to look up the AST-injected
whitelist field and cached the result after the call. For any class the transformer
did not touch - inner-class command objects, precompiled classes, plain POJOs - that
call threw, control jumped past the caching, and the exception was reconstructed on
every subsequent bind. It now uses ReflectionUtils.findField, which returns null, and
caches the negative result too, while still requiring the field to be declared on the
class itself so an untransformed subclass does not inherit its parent's whitelist.
…ing paths

Four lookups repeated per request, all resolving to values that are stable:

- Every redirect read the controller's static namespace field reflectively, through
  a hierarchy walk plus makeAccessible plus Field.get. The in-code comment already
  noted this was avoidable. Now cached per controller Class; a reloaded class is a
  different Class object, so a stale namespace cannot be served.
- Every redirect allocated a ResponseRedirector and called three setters on it. That
  object holds only configuration and takes the request, response and arguments per
  call, so one is now built lazily and reused. Each of its setters clears the cached
  instance, so a configuration change after the first redirect is still honoured.
- Every template render resolved CompositeViewResolver from the bean factory. It is
  now held in a field, matching how this trait already caches the plugin manager,
  mime utility and layout selector.
- The domain map constructor resolved the GrailsApplication and PersistentEntity,
  discarded them, then resolved both again to autowire the instance. They are now
  resolved once and passed down.

The redirector is held in an AtomicReference rather than a volatile field: Groovy's
trait field remapping drops the volatile modifier, and unlike the other cached values
this object is constructed here after its setters run, so it needs safe publication.
GrailsWebRequest.getCurrentRequest() returned the resolved MultipartHttpServletRequest
in place of the request Grails was bound to. That substitution is gone, so the method
is now literally `return getRequest();`.

The two can never disagree. getRequest() is final on Spring's ServletRequestAttributes
and fixed at construction, and nothing wraps or replaces the request for the lifetime of
a GrailsWebRequest: includes and forwards wrap only the response and dispatch the same
request object, layout decoration swaps the response and re-renders against the original
request, and async builds a new GrailsWebRequest around the request it is given. The two
places that do cope with a later request wrapper avoid this method entirely - multipart
through WebUtils.resolveMultipartRequest, and Spring Security by binding a fresh
DelegatingGrailsWebRequest.

All 65 framework call sites now use getRequest(). The method is deprecated rather than
deleted so plugins keep compiling; removing it is a separate decision.

- Move the "always the outermost request" note to the class javadoc, where it outlives
  the deprecated method
- Keep getCurrentRequest in DelegatingGrailsWebRequest's @DeleGate exclusions. Delegating
  it would hand back the request from earlier in the filter chain, which is what that
  filter exists to prevent. Both reasons the exclusion list exists are now written down
- Cover that filter with a spec; it had none
- Stop JsonViewTemplateResolverSpec mocking GrailsWebRequest and stubbing
  getCurrentRequest(). It relied on the deprecated method being the only stubbable
  request accessor and produced an object whose two accessors disagreed; it now drives a
  real GrailsWebRequest over a MockHttpServletRequest
Covers controller action invocation (with and without allowedMethods, and a
command-object action), the interceptor chain with a no-op and an observing
registry, and collectControllerMappings - the uncached wrapper that runs on every
request even when the URL mapping cache hits.

The existing benchmarks measured GrailsWebRequest construction (12 ns) and
multipart resolution (1.7 ns), neither of which is where request time goes.
getRequest() is final on ServletRequestAttributes, so getCurrentRequest() was the
only stubbable request accessor on GrailsWebRequest. Tests that mocked it will see
framework code take a different path now that it calls getRequest() directly.
The filter sets the locale from the request unconditionally, but restored the
previous LocaleContext only on the outermost dispatch. An include or forward
therefore left the enclosing request with the locale it had installed, and replaced
any TimeZoneAwareLocaleContext with a plain SimpleLocaleContext for the remainder
of that request.

The restore now happens on every invocation, matching the unconditional set. Only
the GrailsWebRequest handling stays branched, since an include restores the previous
web request rather than clearing it.

This filter had no test coverage; adds one, including a case that fails without the
change.
…8.0.x

Upstream landed the mass-assignment hardening (apache#15947) and the clearMissing
work (apache#15950), both of which rewrote the DataBindingUtils methods this branch
had touched in "Cache the data binding collaborators and the databinding
whitelist lookup". The conflict is resolved in favour of upstream everywhere
the two overlap, so that the deny-by-default binding behaviour is exactly the
one upstream shipped.

Superseded by upstream and dropped from this branch:

* The whitelist include-list caching in getBindingIncludeList. Upstream's
  rewrite already caches the negative result behind a NO_BINDING_INCLUDE_LIST
  sentinel and resolves the runtime bindable names only on a cache miss, and it
  keys the cache on whether deny-by-default is enabled, which this branch's
  single cache could not express. The method is taken from upstream verbatim.

* The resolveBindingIncludeList helper. Upstream's getField / getPairedField /
  getStaticListFieldValue replace it and fix the same defect: the lookup no
  longer lets getDeclaredField throw for a class the AST transform never
  enhanced, so nothing is owed here any more. The helper also honoured only a
  whitelist declared on the class itself, whereas upstream deliberately walks
  the superclass chain, so DataBindingUtilsSpec now asserts that an inherited
  whitelist applies. Its test of the private include-list cache is dropped: the
  negative result is still covered through the public binding API, and upstream
  now keeps two caches rather than the one the test reached into.

Kept from this branch:

* The ContextBoundBeans cache of the data binding collaborators, which upstream
  does not touch.

* Resolving the GrailsApplication once per bind and passing it down. It now
  travels through a private bindObjectToDomainInstance overload which runs
  upstream's include normalisation, so the include.isEmpty() /
  NO_BINDABLE_PROPERTIES handling and the clearMissing && explicitInclude
  gating apply on every path, including bindToCollection.
…er tests

Holders keeps its application discovery strategies in a static list and consults them in
registration order, and tests share a JVM fork. The spec registered its own strategy but did
not clear the list first, so a strategy left behind by an earlier test - holding an application
context that had since been closed - was asked first and threw IllegalStateException before the
spec's strategy was reached.

Clearing in setup as well as cleanup makes the spec independent of whatever ran before it.
PR apache#16071 landed a `grails-benchmarks` module using the same package root as
`grails-web-benchmarks`, with a comparison tool (`BenchmarkComparator`,
`JmhCompare`, `CommentPoster`, sharding and golden-file tests) that automates
the before/after comparison this branch was doing by hand. Move the
request-path benchmarks into it and delete `grails-web-benchmarks`.

Ported, regrouped into the package-per-subsystem layout the report aggregates
on, and reworked to that module's conventions - benchmarks in `src/jmh/java`,
setup in Groovy fixtures under `src/main/groovy`:

  controllers  ControllerActionBenchmark, ControllerMappingCollectionBenchmark
  interceptors InterceptorChainBenchmark
  web          GrailsWebRequestBenchmark, MultipartResolutionBenchmark,
               RequestPropertyAccessBenchmark

Because the fixtures live in `main`, which the jmh plugin puts on the jmh
compile classpath, the `UrlMappingsDefinition` / `InterceptorFactory` /
`RequestPropertyReader` interfaces and their `Class.forName` lookups are gone -
the Java benchmarks call the Groovy fixtures directly.

`UrlMappingBenchmark` is dropped. Its `matchCachedHit` and
`matchRestfulUriCacheMiss` duplicate `UrlMappingsBenchmark.matchWarmCache` and
`matchColdVariedKeys`. The one shape it measured that upstream did not - a cold
URI that only the catch-all `"/$controller/$action?/$id?"` mapping can serve, so
every earlier mapping is considered and rejected before the match succeeds - is
added to `UrlMappingsBenchmark` as `matchColdCatchAllFallThrough`. On the
existing fixture that costs ~568 ns against ~411 ns for a cold URI the first
mapping serves.

BASELINE.md is dropped: paired before/after numbers are what the new report
tooling produces per pull request. Its measured results, from two full suites
run back to back on an idle M4 Max under JDK 21.0.7 (2 forks, 5x1s warmup +
5x1s measurement), were:

  ControllerActionBenchmark.plainAction                  34.795 ->  3.592  -89.7%
  InterceptorChainBenchmark.oneInterceptorNoOpRegistry  295.293 -> 127.541 -56.8%
  InterceptorChainBenchmark.threeInterceptorsNoOp      1116.942 -> 545.608 -51.2%
  InterceptorChainBenchmark.threeInterceptorsObserving 1972.929 ->1134.393 -42.5%
  GrailsWebRequestBenchmark.construct                    16.283 -> 11.710  -28.1%
  UrlMappingBenchmark.matchRestfulUriCacheMiss         1549.992 ->1287.754 -16.9%
  UrlMappingBenchmark.matchDefaultMappingUriCacheMiss  1881.323 ->1595.361 -15.2%

The request-attribute counts `ControllerActionBenchmark` prints at setup are the
independent evidence for the controller result and are unchanged by the move: an
action on a controller with no `allowedMethods` performs no attribute operations
at all, while one that declares `allowedMethods` still performs 2/1/1.

`grails-benchmarks/build.gradle` gains `:grails-controllers`,
`:grails-web-databinding`, `:grails-mimetypes`, `micrometer-observation` and
`spring-webmvc`. The suite stays opt-in: `build` compiles the benchmarks, only
the explicit `jmh` task runs them.
Three caches were added as Groovy trait fields. A trait is a mixin and its fields are
replicated into every implementing class, so that is per-controller scope for things
that are application scoped. Groovy also remaps trait statics per implementing class,
so the "static" namespace cache was really one Class-keyed map per controller class,
each holding a single entry; and the redirector needed an AtomicReference only because
Groovy silently drops volatile on trait fields.

- The namespace is a static property of the controller class and
  DefaultGrailsControllerClass already resolves it at construction, so the reflective
  read and its cache are both gone - the namespace now comes from the artefact registry,
  keyed on the class issuing the redirect rather than the one currently executing.
- CompositeViewResolver moves to DefaultGrailsApplicationAttributes, alongside the other
  beans it describes as used very often. That object is one instance per servlet context,
  so the resolver is now resolved once for the application rather than once per controller.
- The ResponseRedirector cache is removed rather than relocated. Its inputs are uniformly
  injected, so it is effectively a singleton, but the trait's setters are public API and
  are exercised after construction - RedirectMethodTests registers a listener on a live
  controller and expects the next redirect to notify it - so a shared instance would need
  a per-controller override path anyway. It is built per redirect again, as before.

This also removes the fields from Interceptor, which implements the same trait.
Neither had a benchmark, which is how three unmeasured caches ended up in the
controller traits.
An upload breaching the configured multipart limits fails when the container parses the request
parts, and every parameter read on that request fails with it from then on. Grails reads request
parameters twice before the DispatcherServlet runs - HiddenHttpMethodFilter resolves the _method
override, and GrailsParameterMap is built by any filter ahead of the dispatch, Spring Security
among them. Either read aborted the request inside the filter chain, where no
HandlerExceptionResolver can see it, so the application was left with the servlet container's own
error page: a raw 413 on Tomcat, with the container's error page dispatch double-faulting on the
same unreadable parameters.

Both reads now tolerate a multipart request the container refuses to parse, so the failure is left
for DispatcherServlet.checkMultipart to raise as a MultipartException during dispatch. The
exception reaches the HandlerExceptionResolver chain and the response is rendered through the
application's error dispatch.

The tolerance is confined to multipart requests - an unreadable parameter map on any other request
still propagates - and the parse failure is logged at debug rather than discarded. Such a request
cannot reach a controller either way, because the dispatcher rejects it before handler resolution.

- Add WebUtils.isMultipartContentType, shared by both call sites
- Cover both the tolerated and the still-propagating case in the existing tests

apachegh-16145
app1 runs a real embedded container with the Spring Security filter chain in front of it, which is
the configuration both halves of apachegh-16145 describe. Neither half had a functional test.

- An upload past the configured limit must be rendered by the application's error dispatch rather
  than by the container. Without the accompanying fix this returns Tomcat's own 413 HTML page.
- g:uploadForm(method: 'PUT') emits multipart plus _method, so the override has to keep working for
  a multipart request rather than being skipped along with the parameter read.

The existing specs already cover request.getFile(..) behind the security filter chain, which is the
other behaviour the issue reports as broken.

apachegh-16145
A multipart body the container refuses to parse - an upload past the configured limits - leaves every
parameter read on that request failing from then on. Two of Grails' own reads already tolerated that:
the _method override in HiddenHttpMethodFilter, and the GrailsParameterMap constructor. They were not
the only ones.

ParamsAwareLocaleChangeInterceptor falls back to LocaleChangeInterceptor, which reads the parameter
straight off the request, and it runs on every Grails-mapped dispatch - including the container's error
dispatch for the very failure being reported. That read threw and took the error page down with it: an
oversized upload to an application with a "413" UrlMappings handler returned the container's raw 500
page instead of the mapped response. GrailsExceptionResolver enumerates the request parameters for its
log when grails.exceptionresolver.logRequestParameters is set, which defaults to on in development, and
GroovyPageView reads showSource when it renders a GSP in development - both on that same error path.

The tolerance moves into WebUtils as readParameterMap, readParameter and readParameterNames, so one
place decides what an unreadable multipart request yields, and one place keeps the tolerance confined
to multipart requests. Every framework read goes through it.

Verified against two containers, because the catch is deliberately not container-specific. Tomcat 11
throws org.apache.tomcat.util.http.InvalidParameterException from every parameter accessor; Jetty 12
throws org.eclipse.jetty.http.HttpException$IllegalStateException from getParameterMap while
getParameter and getParameterNames succeed. Catching RuntimeException covers both.

apachegh-16145
A "500" URL mapping that names a controller is reached by forwarding to it. The forward re-enters the
DispatcherServlet, and the forwarded dispatch resolves the same status code mapping again, because the
error status attribute is still on the request. An error handler that fails for a reason belonging to
the request rather than to the moment - an unparseable multipart body, a missing collaborator -
therefore fails again inside its own forward, and that failure resolves straight back into
resolveViewOrForward, which forwards to it again.

Reproduced in grails-test-examples/app4 with an oversized upload, before the framework's parameter
reads were made tolerant: 78,120 nested forwards, StackOverflowError, then OutOfMemoryError while
logging the unwind - 1.9 million lines of log for one request.

The error handler is no longer forwarded to while a forward to it is already running. The repeat
failure is logged and the exception is returned to the DispatcherServlet, which reports it once through
the container. The flag is cleared when the forward returns, so an error handler that ran successfully
leaves a later, unrelated error on the same request free to use it.

The resolver's own request-parameter log is read tolerantly for the same reason: it runs on the error
path, on a request whose parameters may be exactly what the container could not read.

apachegh-16145
app4 gets a "413" status code mapping onto a controller action, which is what the container's error
dispatch has to reach for the failure to be rendered by the application rather than by the container.
That dispatch runs the Grails handler mapping and its interceptors on a request whose parameters cannot
be read, so it is the case the framework's parameter reads have to survive - and the case that was
still broken.

The jetty and undertow examples get the same endpoint, because the tolerance is written against
RuntimeException rather than a container-specific exception type and that reasoning was untested.

Undertow does not behave the same and the spec says so rather than asserting what the others do: it
applies the servlet multipart size limit while reading the request entity and refuses the request at
the HTTP layer, so no filter, handler or status code mapping runs. The response is a bare 413 with an
empty body, and there is nothing the application can contribute to it.

apachegh-16145
- The "413" response code mapping that renders it, and what is and is not available to the action it
  names: the action runs on the container's error dispatch, so params is empty and request.getFile(..)
  is unavailable
- Undertow refusing the request at the HTTP layer, before any application code runs, so no mapping is
  consulted and the body is empty
- The error handler no longer being forwarded to from inside its own forward

apachegh-16145
HiddenHttpMethodFilter.getHttpMethodOverride reads _method on every POST,
including multipart ones, which makes the container parse the request body.
For a request already declared (via Content-Length) larger than the
configured grails.controllers.upload.maxRequestSize, that read was always
going to fail - the tolerant read added in the parent branch catches the
failure, but the parse is still attempted.

Add a Content-Length check ahead of the read: when it's known and over the
configured limit, skip straight to the header fallback. Anything the check
can't rule out (chunked transfer-encoding, no Content-Length) still goes
through the existing tolerant read, so the safety net is unchanged - this
only avoids the doomed attempt for the common declared-length case.

Verified with a throwaway probe against the mock request whose
getParameter() throws (would fail here exactly like the container does):
the oversized case now reaches "POST" without the read ever happening, and
a within-limit multipart request with maxMultipartRequestSize configured
still honours _method. grails-test-examples-app1's FileUploadSpec passes
unchanged against a real embedded Tomcat, including the oversized-upload
and method-override-on-multipart cases.
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