From bc07a451dc5ff7dd9ea7a8be88c412273de05989 Mon Sep 17 00:00:00 2001
From: Brian Clozel <brian.clozel@broadcom.com>
Date: Mon, 16 Mar 2026 11:12:06 +0100
Subject: [PATCH] Fix ParameterizedTypeReference nullness

This commit ensures that `ParameterizedTypeReference<T>` can accept
nullable types. This is especially useful for Kotlin extension functions
and assertion contracts.

Fixes gh-36477
---
 .../core/ParameterizedTypeReference.java               |  2 +-
 .../rsocket/RSocketRequesterExtensionsTests.kt         | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/spring-core/src/main/java/org/springframework/core/ParameterizedTypeReference.java b/spring-core/src/main/java/org/springframework/core/ParameterizedTypeReference.java
index 0191deae128..1953bddc3b9 100644
--- a/spring-core/src/main/java/org/springframework/core/ParameterizedTypeReference.java
+++ b/spring-core/src/main/java/org/springframework/core/ParameterizedTypeReference.java
@@ -42,7 +42,7 @@ import org.springframework.util.Assert;
  * @param <T> the referenced type
  * @see <a href="https://gafter.blogspot.nl/2006/12/super-type-tokens.html">Neal Gafter on Super Type Tokens</a>
  */
-public abstract class ParameterizedTypeReference<T> {
+public abstract class ParameterizedTypeReference<T extends @Nullable Object> {
 
 	private final Type type;
 
diff --git a/spring-messaging/src/test/kotlin/org/springframework/messaging/rsocket/RSocketRequesterExtensionsTests.kt b/spring-messaging/src/test/kotlin/org/springframework/messaging/rsocket/RSocketRequesterExtensionsTests.kt
index 49940f57044..1ab94cddf0e 100644
--- a/spring-messaging/src/test/kotlin/org/springframework/messaging/rsocket/RSocketRequesterExtensionsTests.kt
+++ b/spring-messaging/src/test/kotlin/org/springframework/messaging/rsocket/RSocketRequesterExtensionsTests.kt
@@ -107,35 +107,35 @@ class RSocketRequesterExtensionsTests {
 	suspend fun retrieveAndAwait() {
 		val response = "foo"
 		val retrieveSpec = mockk<RSocketRequester.RetrieveSpec>()
-		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<*>>(stringTypeRefMatcher)) } returns Mono.just("foo")
+		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<String>>(stringTypeRefMatcher)) } returns Mono.just("foo")
 		assertThat(retrieveSpec.retrieveAndAwait<String>()).isEqualTo(response)
 	}
 
 	@Test
 	suspend fun retrieveAndAwaitOrNull() {
 		val retrieveSpec = mockk<RSocketRequester.RetrieveSpec>()
-		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<*>>(stringTypeRefMatcher)) } returns Mono.empty()
+		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<String>>(stringTypeRefMatcher)) } returns Mono.empty()
 		assertThat(retrieveSpec.retrieveAndAwaitOrNull<String>()).isNull()
 	}
 
 	@Test
 	suspend fun retrieveFlow() {
 		val retrieveSpec = mockk<RSocketRequester.RetrieveSpec>()
-		every { retrieveSpec.retrieveFlux(match<ParameterizedTypeReference<*>>(stringTypeRefMatcher)) } returns Flux.just("foo", "bar")
+		every { retrieveSpec.retrieveFlux(match<ParameterizedTypeReference<String>>(stringTypeRefMatcher)) } returns Flux.just("foo", "bar")
 		assertThat(retrieveSpec.retrieveFlow<String>().toList()).contains("foo", "bar")
 	}
 
 	@Test
 	fun retrieveMono() {
 		val retrieveSpec = mockk<RSocketRequester.RetrieveSpec>()
-		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<*>>(stringTypeRefMatcher)) } returns Mono.just("foo")
+		every { retrieveSpec.retrieveMono(match<ParameterizedTypeReference<String>>(stringTypeRefMatcher)) } returns Mono.just("foo")
 		assertThat(retrieveSpec.retrieveMono<String>().block()).isEqualTo("foo")
 	}
 
 	@Test
 	fun retrieveFlux() {
 		val retrieveSpec = mockk<RSocketRequester.RetrieveSpec>()
-		every { retrieveSpec.retrieveFlux(match<ParameterizedTypeReference<*>>(stringTypeRefMatcher)) } returns Flux.just("foo", "bar")
+		every { retrieveSpec.retrieveFlux(match<ParameterizedTypeReference<String>>(stringTypeRefMatcher)) } returns Flux.just("foo", "bar")
 		assertThat(retrieveSpec.retrieveFlux<String>().collectList().block()).contains("foo", "bar")
 	}
 }