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…TTP response **Root Cause:** Several `render()` branches in `ResponseRenderer.groovy` set `webRequest.renderView = false` and wrote content to the response, but never called `response.flushBuffer()`. This left the response uncommitted, causing Spring MVC's `DispatcherServlet` to attempt default view resolution after the action returned, resulting in a `ServletException: Could not resolve view with name '<actionName>'`. **Fix:** Added `response.flushBuffer()` after content is written in every render branch that sets `renderView = false`: 1. `render(Object)` — after writing `object.inspect()` 2. `render(CharSequence)` — after writing and flushing the writer 3. `render(Map, Writable)` — after `renderWritable()` 4. `render(Map)` with `text:` (Writable) — after `renderWritable()` 5. `render(Map)` with `template:` — after all template rendering paths 6. `render(Map)` with `file:` — after `SpringIOUtils.copy()` 7. `renderMarkupInternal()` — after `renderWritable()` (covers `render(Closure)` and `render(Map, Closure)` markup path) 8. `renderJsonInternal()` — after `jsonBuilder.call()` (covers `render(Map, Closure)` JSON path) The `render(Map)` with `status:` branch already had `response.flushBuffer()` — this fix brings all other content-writing branches into parity. **Tests:** Added 10 new Spock feature methods to `ResponseRendererSpec` verifying that `response.isCommitted()` is `true` after each render variant. All 17 tests in the spec pass, the full `grails-controllers` test suite passes, and all violation reports (Checkstyle, CodeNarc, PMD, Repository Conventions) are clean.
jamesfredley
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jamesfredley
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Not approving.
flushBuffer() is not the signal Spring uses to skip view resolution, and render(Map) still has a content-writing branch that does not commit. Details are on the two new calls. A unit test that only asserts MockHttpServletResponse.committed does not reproduce #15819: DispatcherServlet throws Could not resolve view when a ModelAndView is still returned, whether or not the response is committed.
Codex found no defect in the added flush calls themselves. The dispatch contract is outside that diff, and that is what still fails.
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response.flushBuffer() does not stop the exception in #15819.
Spring Framework 7.0.9 DispatcherServlet.processDispatchResult renders whenever the handler returns a non-null, uncleared ModelAndView. It does not consult response.isCommitted(). render() then throws ServletException: Could not resolve view with name '...' if that name does not resolve (DispatcherServlet around the if (mv != null && !mv.wasCleared()) check, and the Could not resolve view with name throw in render()).
On this branch the skip signal is already GrailsWebRequest.renderView. UrlMappingsInfoHandlerAdapter builds the default action view only when the action result is null and webRequest.renderView is true (that property calls isRenderView()). These branches already set the flag to false, so a null return does not reach view resolution. The adapter ignores the flag when the action returns a Map, and when GrailsApplicationAttributes.MODEL_AND_VIEW is already set (UrlMappingsInfoHandlerAdapter lines 164-180). render('ok'); return [foo: 'bar'] still selects the action view after this flush.
Committing here also has a cost. GrailsExceptionResolver only forwards to the error handler when the response is still uncommitted, and later status or header changes cannot take effect. IncludeResponseWrapper.flushBuffer() is a no-op, so this call does not commit an included response either.
Please add a DispatcherServlet-level regression for the reported failure, and make the handler adapter honor response-rendering suppression before it builds an implicit view. Do not treat flushBuffer() as the signal that skips view resolution.
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Agreed. After a second look, the correct fix for #15819 is not in ResponseRenderer.groovy at all — it belongs in UrlMappingsInfoHandlerAdapter.groovy.
Root cause: UrlMappingsInfoHandlerAdapter.handle() only checks webRequest.renderView in the result == null branch. The result instanceof Map and result instanceof ModelAndView branches return a ModelAndView unconditionally, even when render() was called and set renderView = false. If an action calls render(template:...) and then returns a non-null value (or if something sets the MODEL_AND_VIEW request attribute), the adapter returns a ModelAndView to Spring's DispatcherServlet, which then tries to resolve the view and throws Could not resolve view.
The fix — add a !webRequest.renderView guard in UrlMappingsInfoHandlerAdapter after the MODEL_AND_VIEW attribute check (which is the intentional render(view:) path) but before the result instanceof Map / result instanceof ModelAndView / result == null branches:
def modelAndView = request.getAttribute(GrailsApplicationAttributes.MODEL_AND_VIEW)
if (modelAndView instanceof ModelAndView) {
return (ModelAndView) modelAndView // render(view:) — always honour
}
// All other render() variants set renderView=false; don't attempt view resolution
if (!webRequest.renderView) {
return null
}
if (result instanceof Map) { ... return new ModelAndView(...) }
else if (result instanceof ModelAndView) { return result }
else if (result == null) { return new ModelAndView(actionUri) }| input = IOUtils.openStream(new File(o.toString())) | ||
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| SpringIOUtils.copy(input, response.getOutputStream()) | ||
| response.flushBuffer() |
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This is the last new flush in render(Map), but the same method still has a content-writing branch that sets renderView = false and does not commit.
Immediately below, the else if (!statusSet) branch (lines 447-460) does:
webRequest.renderView = false
// JSONElement: renderWritable(...) with no flushBuffer() after it
// otherwise:
response.writer.write(argMap.inspect())render([a: 1]) therefore stays uncommitted, unlike render(someObject) at line 141. The existing RenderMethodTests already exercise this public Map form, and the new spec does not check it.
If the policy is that every content-writing renderView = false branch commits, this branch needs the same flushBuffer() and ControllerExecutionException wrapping, plus a public-API test for render([a: 1]) that checks both the body and isCommitted().
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Agreed. I've backed-out the changes to ResponseRenderer.groovy and associated tests as they do not address the exception thrown in #15819. Instead, I've implemented changes to UrlMappingsInfoHandlerAdapter.groovy and associated tests.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## 8.0.x #16516 +/- ##
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+ Coverage 59.5208% 59.5405% +0.0197%
- Complexity 25014 25019 +5
==================================================
Files 2175 2175
Lines 108636 108637 +1
Branches 19823 19823
==================================================
+ Hits 64661 64683 +22
+ Misses 35020 34999 -21
Partials 8955 8955 🚀 New features to boost your workflow:
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`grails-web-url-mappings/src/main/groovy/org/grails/web/mapping/mvc/UrlMappingsInfoHandlerAdapter.groovy`
— Added `if (!webRequest.renderView) { return null }` guard after the `MODEL_AND_VIEW` attribute check, so the adapter never returns a `ModelAndView` to `DispatcherServlet` when any `render()` variant (other than `render(view:)`) has already handled the response.
- `grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/mvc/UrlMappingsHandlerMappingSpec.groovy` — 3 new `@Issue('apache#15819')` test features proving: (1) `renderView=false` + null return → adapter returns null, (2) `renderView=false` + Map return (the exact bug scenario) → adapter returns null, (3) `render(view:)` path → adapter returns the ModelAndView.
Both `grails-controllers` and `grails-web-url-mappings` full test suites pass (BUILD SUCCESSFUL, 171 tasks).
🔎 No tests executed 🔎🏷️ Commit: bde8bf0 Learn more about TestLens at testlens.app/docs. |
ruthst00
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Description
Root Cause:
UrlMappingsInfoHandlerAdapter.handle()only checkswebRequest.renderViewin theresult == nullbranch. Theresult instanceof Mapandresult instanceof ModelAndViewbranches return aModelAndViewunconditionally, even whenrender()was called and setrenderView = false. If an action callsrender(template:...)and then returns a non-null value (or if something sets theMODEL_AND_VIEWrequest attribute), the adapter returns aModelAndViewto Spring'sDispatcherServlet, which then tries to resolve the view and throwsCould not resolve view.The fix — add a
!webRequest.renderViewguard inUrlMappingsInfoHandlerAdapterafter theMODEL_AND_VIEWattribute check (which is the intentionalrender(view:)path) but before theresult instanceof Map/result instanceof ModelAndView/result == nullbranches:Files changed:
grails-web-url-mappings/src/main/groovy/org/grails/web/mapping/mvc/UrlMappingsInfoHandlerAdapter.groovyif (!webRequest.renderView) { return null }guard after theMODEL_AND_VIEWattribute check, so the adapter never returns aModelAndViewtoDispatcherServletwhen anyrender()variant (other thanrender(view:)) has already handled the response.grails-web-url-mappings/src/test/groovy/org/grails/web/mapping/mvc/UrlMappingsHandlerMappingSpec.groovy@Issue('#15819')test features proving: (1)renderView=false+ null return → adapter returns null, (2)renderView=false+ Map return (the exact bug scenario) → adapter returns null, (3)render(view:)path → adapter returns the ModelAndView.Why we don't need a test that confirms the exception described in #15819 is not thrown when the response is left uncommitted after the action returns:
Issue #15819 says the exception is thrown by
DispatcherServlet.processDispatchResultwhen it receives a non-nullModelAndViewand tries to resolve the view. Our current tests verify the adapter returnsnull, but they don't exerciseDispatcherServletat all — so they don't prove the exception isn't thrown end-to-end.However, a
DispatcherServlet-level test is not needed, and adding one would test Spring's behaviour rather than our fix. The exception in #15819 is thrown byDispatcherServlet.processDispatchResultonly whenUrlMappingsInfoHandlerAdapter.handle()returns a non-nullModelAndViewwith an unresolvable view name. Our fix is entirely insidehandle(). The three new tests prove the complete contract at the right level:renderView=false(anyrender()variant exceptrender(view:)),handle()returnsnull→DispatcherServletnever reaches view resolution → the exception cannot be thrown.render(view:)is used (setsMODEL_AND_VIEWattribute),handle()returns theModelAndView→ view resolution proceeds as intended.Moreover, a
DispatcherServlet-level test would require wiring up aViewResolverthat deliberately fails, just to prove that Spring's dispatch loop doesn't call it whenhandle()returnsnull. That tests Spring's own logic (already covered by Spring's test suite), not our fix. The unit-level contract test directly asserts the output of the method whose bug we fixed — that is the correct and sufficient level of abstraction.Fixes #15819
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