diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/config/package-info.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/config/package-info.java
index 81af3146f7a..7aaeacd51a0 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/config/package-info.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/config/package-info.java
@@ -1,4 +1,5 @@
 /**
  * Provides classes for configuration - parsers, namespace handlers.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.webflux.config;
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFlux.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFlux.java
index 4fec971648b..a55fc16feca 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFlux.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFlux.java
@@ -19,10 +19,11 @@
 import java.net.URI;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.expression.Expression;
 import org.springframework.integration.expression.FunctionExpression;
 import org.springframework.integration.webflux.inbound.WebFluxInboundEndpoint;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.web.reactive.function.client.WebClient;
 
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
index f5d78ec4375..99766144ebe 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/WebFluxMessageHandlerSpec.java
@@ -19,6 +19,8 @@
 import java.net.URI;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.expression.Expression;
 import org.springframework.expression.common.LiteralExpression;
@@ -27,7 +29,6 @@
 import org.springframework.integration.expression.ValueExpression;
 import org.springframework.integration.http.dsl.BaseHttpMessageHandlerSpec;
 import org.springframework.integration.webflux.outbound.WebFluxRequestExecutingMessageHandler;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.web.reactive.function.BodyExtractor;
 import org.springframework.web.reactive.function.client.WebClient;
@@ -47,8 +48,7 @@
 public class WebFluxMessageHandlerSpec
 		extends BaseHttpMessageHandlerSpec<WebFluxMessageHandlerSpec, WebFluxRequestExecutingMessageHandler> {
 
-	@Nullable
-	protected final WebClient webClient; // NOSONAR - final
+	protected final @Nullable WebClient webClient;
 
 	protected WebFluxMessageHandlerSpec(URI uri, @Nullable WebClient webClient) {
 		this(new ValueExpression<>(uri), webClient);
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/package-info.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/package-info.java
index 961f399976e..aa14b092595 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/package-info.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/dsl/package-info.java
@@ -1,6 +1,5 @@
 /**
  * Provides WebFlux Components support for Spring Integration Java DSL.
  */
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.webflux.dsl;
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxInboundEndpoint.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxInboundEndpoint.java
index 68b4a552ddc..16c8ed1c383 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxInboundEndpoint.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxInboundEndpoint.java
@@ -27,6 +27,7 @@
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
+import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -458,7 +459,7 @@ private List<MediaType> getProducibleMediaTypes(ResolvableType elementType) {
 				.collect(Collectors.toList());
 	}
 
-	private MediaType selectMediaType(ServerWebExchange exchange, Supplier<List<MediaType>> producibleTypesSupplier) {
+	private @Nullable MediaType selectMediaType(ServerWebExchange exchange, Supplier<List<MediaType>> producibleTypesSupplier) {
 		List<MediaType> acceptableTypes = getAcceptableTypes(exchange);
 		List<MediaType> producibleTypes = getProducibleTypes(exchange, producibleTypesSupplier);
 
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxIntegrationRequestMappingHandlerMapping.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxIntegrationRequestMappingHandlerMapping.java
index 02524525575..53fcc6388a6 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxIntegrationRequestMappingHandlerMapping.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/WebFluxIntegrationRequestMappingHandlerMapping.java
@@ -21,6 +21,8 @@
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
 import org.springframework.context.ApplicationListener;
@@ -86,6 +88,7 @@
 public class WebFluxIntegrationRequestMappingHandlerMapping extends RequestMappingHandlerMapping
 		implements ApplicationListener<ContextRefreshedEvent>, DestructionAwareBeanPostProcessor {
 
+	@SuppressWarnings("NullAway") // Reflection
 	private static final Method HANDLER_METHOD =
 			ReflectionUtils.findMethod(WebHandler.class, "handle", ServerWebExchange.class);
 
@@ -103,7 +106,10 @@ public Object postProcessBeforeInitialization(Object bean, String beanName) thro
 	@Override
 	public void postProcessBeforeDestruction(Object bean, String beanName) throws BeansException {
 		if (isHandler(bean.getClass())) {
-			unregisterMapping(getMappingForEndpoint((WebFluxInboundEndpoint) bean));
+			RequestMappingInfo mapping = getMappingForEndpoint((WebFluxInboundEndpoint) bean);
+			if (mapping != null) {
+				unregisterMapping(mapping);
+			}
 		}
 	}
 
@@ -118,13 +124,14 @@ protected boolean isHandler(Class<?> beanType) {
 	}
 
 	@Override
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	protected void detectHandlerMethods(Object handler) {
 		if (handler instanceof String string) {
-			handler = getApplicationContext().getBean(string); // NOSONAR never null
+			handler = getApplicationContext().getBean(string);
 		}
 		RequestMappingInfo mapping = getMappingForEndpoint((WebFluxInboundEndpoint) handler);
 		if (mapping != null) {
-			registerMapping(mapping, handler, HANDLER_METHOD); // NOSONAR never null
+			registerMapping(mapping, handler, HANDLER_METHOD);
 		}
 	}
 
@@ -134,7 +141,7 @@ protected void detectHandlerMethods(Object handler) {
 	 * {@link org.springframework.integration.http.inbound.RequestMapping}.
 	 * @see RequestMappingHandlerMapping#getMappingForMethod
 	 */
-	private RequestMappingInfo getMappingForEndpoint(WebFluxInboundEndpoint endpoint) {
+	private @Nullable RequestMappingInfo getMappingForEndpoint(WebFluxInboundEndpoint endpoint) {
 		org.springframework.web.bind.annotation.RequestMapping requestMappingAnnotation =
 				HttpContextUtils.convertRequestMappingToAnnotation(endpoint.getRequestMapping());
 		if (requestMappingAnnotation != null) {
@@ -146,7 +153,7 @@ private RequestMappingInfo getMappingForEndpoint(WebFluxInboundEndpoint endpoint
 	}
 
 	@Override
-	protected CorsConfiguration initCorsConfiguration(Object handler, Method method, RequestMappingInfo mappingInfo) {
+	protected @Nullable CorsConfiguration initCorsConfiguration(Object handler, Method method, RequestMappingInfo mappingInfo) {
 		CrossOrigin crossOrigin = ((BaseHttpInboundEndpoint) handler).getCrossOrigin();
 		if (crossOrigin != null) {
 			return buildCorsConfiguration(crossOrigin, mappingInfo);
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/package-info.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/package-info.java
index 5dd7f19ba75..bf26044da29 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/package-info.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/inbound/package-info.java
@@ -1,4 +1,5 @@
 /**
  * Provides classes supporting inbound endpoints.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.webflux.inbound;
diff --git a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/support/package-info.java b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/support/package-info.java
index e9427f0978d..ff6afa3b241 100644
--- a/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/support/package-info.java
+++ b/spring-integration-webflux/src/main/java/org/springframework/integration/webflux/support/package-info.java
@@ -1,4 +1,5 @@
 /**
  * Provides classes to support WebFlux endpoints.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.webflux.support;