From bcd78a2ccc9e37bf99bc05cc5f4016d7ce2dd830 Mon Sep 17 00:00:00 2001
From: Brian Clozel <brian.clozel@broadcom.com>
Date: Thu, 10 Sep 2026 15:17:23 +0200
Subject: [PATCH] Add implementation note in DefaultAsyncServerResponse

See gh-37257
---
 .../web/servlet/function/DefaultAsyncServerResponse.java        | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultAsyncServerResponse.java b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultAsyncServerResponse.java
index 1ba7faf03cc..5d881b54943 100644
--- a/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultAsyncServerResponse.java
+++ b/spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultAsyncServerResponse.java
@@ -116,6 +116,8 @@ final class DefaultAsyncServerResponse extends ErrorHandlingServerResponse imple
 
 		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
 		AsyncWebRequest asyncWebRequest = asyncManager.getAsyncWebRequest();
+		// defensive check as asyncWebRequest should not be null,
+		// should have been set already in HandlerFunctionAdapter#getWebAsyncManager
 		if (asyncWebRequest == null) {
 			asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
 			asyncManager.setAsyncWebRequest(asyncWebRequest);