Add BlockingExecutionConfigurer to WebFlux config

Closes gh-30678

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestMappingIntegrationTests.java

@@ -18,6 +18,8 @@ package org.springframework.web.reactive.result.method.annotation;
 
 import java.net.URI;
 import java.time.Duration;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Predicate;
 
 import org.reactivestreams.Publisher;
 
@@ -25,6 +27,8 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.ReactiveAdapterRegistry;
+import org.springframework.core.task.AsyncTaskExecutor;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
@@ -33,7 +37,10 @@ import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.method.HandlerMethod;
+import org.springframework.web.reactive.config.BlockingExecutionConfigurer;
 import org.springframework.web.reactive.config.EnableWebFlux;
+import org.springframework.web.reactive.config.WebFluxConfigurer;
 import org.springframework.web.server.adapter.ForwardedHeaderTransformer;
 import org.springframework.web.testfixture.http.server.reactive.bootstrap.HttpServer;
 
@@ -70,6 +77,9 @@ class RequestMappingIntegrationTests extends AbstractRequestMappingIntegrationTe
 
 		url += "/";
 		assertThat(getRestTemplate().getForObject(url, String.class)).isEqualTo("root");
+
+		assertThat(getApplicationContext().getBean(TestExecutor.class).invocationCount.get()).isEqualTo(2);
+		assertThat(getApplicationContext().getBean(TestPredicate.class).invocationCount.get()).isEqualTo(2);
 	}
 
 	@ParameterizedHttpServerTest
@@ -109,7 +119,34 @@ class RequestMappingIntegrationTests extends AbstractRequestMappingIntegrationTe
 
 	@Configuration
 	@EnableWebFlux
-	static class WebConfig {
+	static class WebConfig implements WebFluxConfigurer {
+
+		@Override
+		public void configureBlockingExecution(BlockingExecutionConfigurer configurer) {
+			configurer.setExecutor(executor());
+			configurer.setControllerMethodPredicate(predicate());
+		}
+
+		@Bean
+		TestExecutor executor() {
+			return new TestExecutor();
+		}
+
+		@Bean
+		TestPredicate predicate() {
+			return new TestPredicate();
+		}
+
+	}
+
+
+	@Configuration
+	static class LocalConfig {
+
+		@Bean
+		public ForwardedHeaderTransformer forwardedHeaderTransformer() {
+			return new ForwardedHeaderTransformer();
+		}
 	}
 
 
@@ -145,12 +182,27 @@ class RequestMappingIntegrationTests extends AbstractRequestMappingIntegrationTe
 	}
 
 
-	@Configuration
-	static class LocalConfig {
+	private static class TestExecutor implements AsyncTaskExecutor {
 
-		@Bean
-		public ForwardedHeaderTransformer forwardedHeaderTransformer() {
-			return new ForwardedHeaderTransformer();
+		private final AtomicInteger invocationCount = new AtomicInteger();
+
+		@Override
+		public void execute(Runnable task) {
+			this.invocationCount.incrementAndGet();
+			task.run();
+		}
+	}
+
+
+	private static class TestPredicate implements Predicate<HandlerMethod> {
+
+		private final AtomicInteger invocationCount = new AtomicInteger();
+
+		@Override
+		public boolean test(HandlerMethod handlerMethod) {
+			this.invocationCount.incrementAndGet();
+			Class<?> returnType = handlerMethod.getReturnType().getParameterType();
+			return (ReactiveAdapterRegistry.getSharedInstance().getAdapter(returnType) == null);
 		}
 	}