Adapt to Reactor 3.8 JSpecify annotations

framework-platform/framework-platform.gradle

@@ -10,7 +10,7 @@ dependencies {
 	api(platform("com.fasterxml.jackson:jackson-bom:2.20.0"))
 	api(platform("io.micrometer:micrometer-bom:1.16.0-M3"))
 	api(platform("io.netty:netty-bom:4.2.6.Final"))
-	api(platform("io.projectreactor:reactor-bom:2025.0.0-M7"))
+	api(platform("io.projectreactor:reactor-bom:2025.0.0-SNAPSHOT"))
 	api(platform("io.rsocket:rsocket-bom:1.1.5"))
 	api(platform("org.apache.groovy:groovy-bom:5.0.0-rc-1"))
 	api(platform("org.apache.logging.log4j:log4j-bom:3.0.0-beta3"))

spring-context/src/main/java/org/springframework/cache/interceptor/CacheAspectSupport.java

@@ -23,6 +23,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
@@ -1170,7 +1171,7 @@ private class ReactiveCachingHandler {
 						if (invokeFailure.get()) {
 							return Mono.error(ex);
 						}
-						return (Mono) invokeOperation(invoker);
+						return (Mono) Objects.requireNonNull(invokeOperation(invoker));
 					}
 					catch (RuntimeException exception) {
 						return Mono.error(exception);
@@ -1201,8 +1202,8 @@ private class ReactiveCachingHandler {
 				}
 				if (adapter.isMultiValue()) {
 					return adapter.fromPublisher(Flux.from(Mono.fromFuture(cachedFuture))
-							.switchIfEmpty(Flux.defer(() -> (Flux) evaluate(null, invoker, method, contexts)))
-							.flatMap(v -> evaluate(valueToFlux(v, contexts), invoker, method, contexts))
+							.switchIfEmpty(Flux.defer(() -> (Flux) Objects.requireNonNull(evaluate(null, invoker, method, contexts))))
+							.flatMap(v -> Objects.requireNonNull(evaluate(valueToFlux(v, contexts), invoker, method, contexts)))
 							.onErrorResume(RuntimeException.class, ex -> {
 								try {
 									getErrorHandler().handleCacheGetError((RuntimeException) ex, cache, key);
@@ -1216,8 +1217,11 @@ private class ReactiveCachingHandler {
 				}
 				else {
 					return adapter.fromPublisher(Mono.fromFuture(cachedFuture)
-							.switchIfEmpty(Mono.defer(() -> (Mono) evaluate(null, invoker, method, contexts)))
-							.flatMap(v -> evaluate(Mono.justOrEmpty(unwrapCacheValue(v)), invoker, method, contexts))
+					                                 // TODO: requireNonNull is not for
+					                                 //  free, perhaps we should
+					                                 //  suppress it
+							.switchIfEmpty(Mono.defer(() -> (Mono) Objects.requireNonNull(evaluate(null, invoker, method, contexts))))
+							.flatMap(v -> Objects.requireNonNull(evaluate(Mono.justOrEmpty(unwrapCacheValue(v)), invoker, method, contexts)))
 							.onErrorResume(RuntimeException.class, ex -> {
 								try {
 									getErrorHandler().handleCacheGetError((RuntimeException) ex, cache, key);

spring-core/src/main/java/org/springframework/core/codec/AbstractDataBufferDecoder.java

@@ -17,6 +17,7 @@
 package org.springframework.core.codec;
 
 import java.util.Map;
+import java.util.function.Function;
 
 import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Publisher;
@@ -84,15 +85,18 @@ public int getMaxInMemorySize() {
 	public Flux<T> decode(Publisher<DataBuffer> input, ResolvableType elementType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
-		return Flux.from(input).map(buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints));
+		Function<DataBuffer, @Nullable T> decodeBufferFn =
+				buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints);
+		return Flux.from(input).map(decodeBufferFn);
 	}
 
 	@Override
 	public Mono<T> decodeToMono(Publisher<DataBuffer> input, ResolvableType elementType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
-		return DataBufferUtils.join(input, this.maxInMemorySize)
-				.map(buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints));
+		Function<DataBuffer, @Nullable T> decodeBufferFn =
+				buffer -> decodeDataBuffer(buffer, elementType, mimeType, hints);
+		return DataBufferUtils.join(input, this.maxInMemorySize).map(decodeBufferFn);
 	}
 
 	/**

spring-messaging/src/main/java/org/springframework/messaging/handler/annotation/reactive/PayloadMethodArgumentResolver.java

@@ -20,6 +20,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.function.Consumer;
 
 import org.apache.commons.logging.Log;
@@ -227,7 +228,7 @@ private Mono<Object> decodeContent(MethodParameter parameter, Message<?> message
 				if (adapter != null && adapter.isMultiValue()) {
 					Flux<?> flux = content
 							.filter(this::nonEmptyDataBuffer)
-							.map(buffer -> decoder.decode(buffer, elementType, mimeType, hints))
+							.map(buffer -> Objects.requireNonNull(decoder.decode(buffer, elementType, mimeType, hints)))
 							.onErrorMap(ex -> handleReadError(parameter, message, ex));
 					if (isContentRequired) {
 						flux = flux.switchIfEmpty(Flux.error(() -> handleMissingBody(parameter, message)));
@@ -241,7 +242,7 @@ private Mono<Object> decodeContent(MethodParameter parameter, Message<?> message
 					// Single-value (with or without reactive type wrapper)
 					Mono<?> mono = content.next()
 							.filter(this::nonEmptyDataBuffer)
-							.map(buffer -> decoder.decode(buffer, elementType, mimeType, hints))
+							.map(buffer -> Objects.requireNonNull(decoder.decode(buffer, elementType, mimeType, hints)))
 							.onErrorMap(ex -> handleReadError(parameter, message, ex));
 					if (isContentRequired) {
 						mono = mono.switchIfEmpty(Mono.error(() -> handleMissingBody(parameter, message)));

spring-messaging/src/main/java/org/springframework/messaging/rsocket/DefaultRSocketRequester.java

@@ -18,6 +18,7 @@
 
 import java.util.Collections;
 import java.util.Map;
+import java.util.Objects;
 import java.util.function.Consumer;
 
 import io.rsocket.Payload;
@@ -291,7 +292,7 @@ private <T> Mono<T> retrieveMono(ResolvableType elementType) {
 
 			Decoder<?> decoder = strategies.decoder(elementType, dataMimeType);
 			return (Mono<T>) payloadMono.map(this::retainDataAndReleasePayload)
-					.map(dataBuffer -> decoder.decode(dataBuffer, elementType, dataMimeType, EMPTY_HINTS));
+					.map(dataBuffer -> Objects.requireNonNull(decoder.decode(dataBuffer, elementType, dataMimeType, EMPTY_HINTS)));
 		}
 
 		@Override
@@ -317,7 +318,7 @@ private <T> Flux<T> retrieveFlux(ResolvableType elementType) {
 
 			Decoder<?> decoder = strategies.decoder(elementType, dataMimeType);
 			return payloadFlux.map(this::retainDataAndReleasePayload).map(dataBuffer ->
-					(T) decoder.decode(dataBuffer, elementType, dataMimeType, EMPTY_HINTS));
+					(T) Objects.requireNonNull(decoder.decode(dataBuffer, elementType, dataMimeType, EMPTY_HINTS)));
 		}
 
 		private Mono<Payload> getPayloadMono() {

spring-r2dbc/src/main/java/org/springframework/r2dbc/connection/SingleConnectionFactory.java

@@ -20,6 +20,7 @@
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
+import java.util.Objects;
 import java.util.concurrent.atomic.AtomicReference;
 
 import io.r2dbc.spi.Connection;
@@ -176,7 +177,7 @@ public Mono<? extends Connection> create() {
 				this.connection =
 						(isSuppressClose() ? getCloseSuppressingConnectionProxy(connectionToUse) : connectionToUse);
 			}
-			return this.connection;
+			return Objects.requireNonNull(this.connection);
 		}).flatMap(this::prepareConnection);
 	}
 

spring-tx/src/main/java/org/springframework/transaction/interceptor/TransactionAspectSupport.java

@@ -17,6 +17,7 @@
 package org.springframework.transaction.interceptor;
 
 import java.lang.reflect.Method;
+import java.util.Objects;
 import java.util.Properties;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ExecutionException;
@@ -903,7 +904,7 @@ public Object invokeWithinTransaction(Method method, @Nullable Class<?> targetCl
 								createTransactionIfNecessary(rtm, txAttr, joinpointIdentification),
 								tx -> {
 									try {
-										return (Mono<?>) invocation.proceedWithInvocation();
+										return (Mono<?>) Objects.requireNonNull(invocation.proceedWithInvocation());
 									}
 									catch (Throwable ex) {
 										return Mono.error(ex);

spring-tx/src/test/kotlin/org/springframework/transaction/interceptor/AbstractCoroutinesTransactionAspectTests.kt

@@ -301,7 +301,7 @@ abstract class AbstractCoroutinesTransactionAspectTests {
 
 	private fun checkReactiveTransaction(expected: Boolean) {
 		Mono.deferContextual{context -> Mono.just(context)}
-				.handle { context: ContextView, sink: SynchronousSink<Any?> ->
+				.handle { context: ContextView, sink: SynchronousSink<ContextView> ->
 					if (context.hasKey(TransactionContext::class.java) != expected) {
 						Fail.fail<Any>("Should have thrown NoTransactionException")
 					}

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpConnector.java

@@ -165,8 +165,9 @@ public Mono<ClientHttpResponse> connect(HttpMethod method, URI uri,
 		return requestSender
 				.send((request, outbound) -> requestCallback.apply(adaptRequest(method, uri, request, outbound)))
 				.responseConnection((response, connection) -> {
-					responseRef.set(new ReactorClientHttpResponse(response, connection));
-					return Mono.just((ClientHttpResponse) responseRef.get());
+					ReactorClientHttpResponse clientResponse = new ReactorClientHttpResponse(response, connection);
+					responseRef.set(clientResponse);
+					return Mono.just((ClientHttpResponse) clientResponse);
 				})
 				.next()
 				.doOnCancel(() -> {

spring-web/src/test/kotlin/org/springframework/http/codec/cbor/KotlinSerializationCborEncoderTests.kt

@@ -66,10 +66,10 @@ class KotlinSerializationCborEncoderTests : AbstractEncoderTests<KotlinSerializa
 				pojo3
 		)
 		val pojoBytes = Cbor.Default.encodeToByteArray(arrayOf(pojo1, pojo2, pojo3))
-		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer?> ->
+		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer> ->
 			step
 				.consumeNextWith(expectBytes(pojoBytes)
-					.andThen { dataBuffer: DataBuffer? -> DataBufferUtils.release(dataBuffer) })
+					.andThen { dataBuffer: DataBuffer -> DataBufferUtils.release(dataBuffer) })
 				.verifyComplete()
 		}
 	}
@@ -78,7 +78,7 @@ class KotlinSerializationCborEncoderTests : AbstractEncoderTests<KotlinSerializa
 	fun encodeMono() {
 		val pojo = Pojo("foo", "bar")
 		val input = Mono.just(pojo)
-		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer?> ->
+		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer> ->
 			step
 				.consumeNextWith(expectBytes(Cbor.Default.encodeToByteArray(pojo))
 					.andThen { dataBuffer: DataBuffer? -> DataBufferUtils.release(dataBuffer) })

spring-web/src/test/kotlin/org/springframework/http/codec/json/CustomKotlinSerializationJsonEncoderTests.kt

@@ -45,9 +45,9 @@ class CustomKotlinSerializationJsonEncoderTests :
 	@Test
 	override fun encode() {
 		val input = Mono.just(BigDecimal(1))
-		testEncode(input, BigDecimal::class.java) { step: StepVerifier.FirstStep<DataBuffer?> ->
+		testEncode(input, BigDecimal::class.java) { step: StepVerifier.FirstStep<DataBuffer> ->
 			step.consumeNextWith(expectString("1.0")
-					.andThen { dataBuffer: DataBuffer? -> DataBufferUtils.release(dataBuffer) })
+					.andThen { dataBuffer: DataBuffer -> DataBufferUtils.release(dataBuffer) })
 					.verifyComplete()
 		}
 	}

spring-web/src/test/kotlin/org/springframework/http/codec/protobuf/KotlinSerializationProtobufEncoderTests.kt

@@ -76,10 +76,10 @@ class KotlinSerializationProtobufEncoderTests : AbstractEncoderTests<KotlinSeria
 				pojo3
 		)
 		val pojoBytes = ProtoBuf.Default.encodeToByteArray(arrayOf(pojo1, pojo2, pojo3))
-		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer?> ->
+		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer> ->
 			step
 				.consumeNextWith(expectBytes(pojoBytes)
-					.andThen { dataBuffer: DataBuffer? -> DataBufferUtils.release(dataBuffer) })
+					.andThen { dataBuffer: DataBuffer -> DataBufferUtils.release(dataBuffer) })
 				.verifyComplete()
 		}
 	}
@@ -88,10 +88,10 @@ class KotlinSerializationProtobufEncoderTests : AbstractEncoderTests<KotlinSeria
 	fun encodeMono() {
 		val pojo = Pojo("foo", "bar")
 		val input = Mono.just(pojo)
-		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer?> ->
+		testEncode(input, Pojo::class.java) { step: FirstStep<DataBuffer> ->
 			step
 				.consumeNextWith(expectBytes(ProtoBuf.Default.encodeToByteArray(pojo))
-					.andThen { dataBuffer: DataBuffer? -> DataBufferUtils.release(dataBuffer) })
+					.andThen { dataBuffer: DataBuffer -> DataBufferUtils.release(dataBuffer) })
 				.verifyComplete()
 		}
 	}

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/SessionAttributeMethodArgumentResolver.java

@@ -16,6 +16,9 @@
 
 package org.springframework.web.reactive.result.method.annotation;
 
+import java.util.function.Function;
+
+import org.jspecify.annotations.Nullable;
 import reactor.core.publisher.Mono;
 
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
@@ -26,6 +29,7 @@
 import org.springframework.web.bind.annotation.ValueConstants;
 import org.springframework.web.server.MissingRequestValueException;
 import org.springframework.web.server.ServerWebExchange;
+import org.springframework.web.server.WebSession;
 
 /**
  * Resolves method arguments annotated with an @{@link SessionAttribute}.
@@ -55,9 +59,8 @@ protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
 
 	@Override
 	protected Mono<Object> resolveName(String name, MethodParameter parameter, ServerWebExchange exchange) {
-		return exchange.getSession()
-				.filter(session -> session.getAttribute(name) != null)
-				.map(session -> session.getAttribute(name));
+		Function<WebSession, @Nullable Object> extractAttributeFn = session -> session.getAttribute(name);
+		return exchange.getSession().mapNotNull(extractAttributeFn);
 	}
 
 	@Override

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDsl.kt

@@ -739,7 +739,8 @@ class CoRouterFunctionDsl internal constructor (private val init: (CoRouterFunct
 	}
 
 	@PublishedApi
-	internal fun <T> asMono(request: ServerRequest, context: CoroutineContext = Dispatchers.Unconfined, handler: suspend (ServerRequest) -> T): Mono<T> {
+	internal fun <T : Any> asMono(request: ServerRequest, context: CoroutineContext =
+		Dispatchers.Unconfined, handler: suspend (ServerRequest) -> T?): Mono<T> {
 		return mono(context) {
 			contextProvider?.let {
 				withContext(it.invoke(request)) {

spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/InvocableHandlerMethodKotlinTests.kt

@@ -381,7 +381,8 @@ class InvocableHandlerMethodKotlinTests {
 		StepVerifier.create(mono)
 				.consumeNextWith {
 					if (it.returnValue is Mono<*>) {
-						StepVerifier.create(it.returnValue as Mono<*>).expectNext(expected).verifyComplete()
+						StepVerifier.create(it.returnValue as Mono<*>).expectNext(requireNotNull(expected))
+							.verifyComplete()
 					} else {
 						assertThat(it.returnValue).isEqualTo(expected)
 					}