Improve toString for reactive ScheduledTask

Prior to this commit, the reactive Scheduled tasks would be wrapped as a
`SubscribingRunnable` which does not implement a custom `toString`. This
would result in task metadata using the default Java `toString`
representation for those.

This commit ensures that the bean class name and method name are used
for this `toString`.

Closes gh-34010

Author: bclozel

Diff for: spring-context/src/main/java/org/springframework/scheduling/annotation/ScheduledAnnotationReactiveSupport.java

@@ -123,8 +123,9 @@ public static Runnable createSubscriptionRunnable(Method method, Object targetBe
 		Publisher<?> publisher = getPublisherFor(method, targetBean);
 		Supplier<ScheduledTaskObservationContext> contextSupplier =
 				() -> new ScheduledTaskObservationContext(targetBean, method);
+		String displayName = targetBean.getClass().getName() + "." + method.getName();
 		return new SubscribingRunnable(publisher, shouldBlock, scheduled.scheduler(),
-				subscriptionTrackerRegistry, observationRegistrySupplier, contextSupplier);
+				subscriptionTrackerRegistry, displayName, observationRegistrySupplier, contextSupplier);
 	}
 
 	/**
@@ -192,6 +193,8 @@ static final class SubscribingRunnable implements SchedulingAwareRunnable {
 
 		final boolean shouldBlock;
 
+		final String displayName;
+
 		@Nullable
 		private final String qualifier;
 
@@ -202,12 +205,13 @@ static final class SubscribingRunnable implements SchedulingAwareRunnable {
 		final Supplier<ScheduledTaskObservationContext> contextSupplier;
 
 		SubscribingRunnable(Publisher<?> publisher, boolean shouldBlock,
-				@Nullable String qualifier, List<Runnable> subscriptionTrackerRegistry,
-				Supplier<ObservationRegistry> observationRegistrySupplier,
-				Supplier<ScheduledTaskObservationContext> contextSupplier) {
+							@Nullable String qualifier, List<Runnable> subscriptionTrackerRegistry,
+							String displayName, Supplier<ObservationRegistry> observationRegistrySupplier,
+							Supplier<ScheduledTaskObservationContext> contextSupplier) {
 
 			this.publisher = publisher;
 			this.shouldBlock = shouldBlock;
+			this.displayName = displayName;
 			this.qualifier = qualifier;
 			this.subscriptionTrackerRegistry = subscriptionTrackerRegistry;
 			this.observationRegistrySupplier = observationRegistrySupplier;
@@ -253,6 +257,11 @@ private void subscribe(TrackingSubscriber subscriber, Observation observation) {
 				this.publisher.subscribe(subscriber);
 			}
 		}
+
+		@Override
+		public String toString() {
+			return this.displayName;
+		}
 	}
 
 

Diff for: spring-context/src/test/java/org/springframework/scheduling/annotation/ScheduledAnnotationReactiveSupportTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -173,6 +173,17 @@ void hasCheckpointToString() {
 		assertThat(p).hasToString("checkpoint(\"@Scheduled 'mono()' in 'org.springframework.scheduling.annotation.ScheduledAnnotationReactiveSupportTests$ReactiveMethods'\")");
 	}
 
+	@Test
+	void shouldProvideToString() {
+		ReactiveMethods target = new ReactiveMethods();
+		Method m = ReflectionUtils.findMethod(ReactiveMethods.class, "mono");
+		Scheduled cron = AnnotationUtils.synthesizeAnnotation(Map.of("cron", "-"), Scheduled.class, null);
+		List<Runnable> tracker = new ArrayList<>();
+
+		assertThat(createSubscriptionRunnable(m, target, cron, () -> ObservationRegistry.NOOP, tracker))
+				.hasToString("org.springframework.scheduling.annotation.ScheduledAnnotationReactiveSupportTests$ReactiveMethods.mono");
+	}
+
 
 	static class ReactiveMethods {