Consolidate default WebMvc executor log warnings

Closes gh-30902

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/context/request/async/WebAsyncManager.java

@@ -30,7 +30,6 @@
 
 import org.springframework.core.task.AsyncTaskExecutor;
 import org.springframework.core.task.SimpleAsyncTaskExecutor;
-import org.springframework.core.task.SyncTaskExecutor;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.web.context.request.RequestAttributes;
@@ -74,8 +73,6 @@ public final class WebAsyncManager {
 	private static final DeferredResultProcessingInterceptor timeoutDeferredResultInterceptor =
 			new TimeoutDeferredResultProcessingInterceptor();
 
-	private static Boolean taskExecutorWarning = true;
-
 
 	@Nullable
 	private AsyncWebRequest asyncWebRequest;
@@ -295,9 +292,6 @@ public void startCallableProcessing(final WebAsyncTask<?> webAsyncTask, Object..
 		if (executor != null) {
 			this.taskExecutor = executor;
 		}
-		else {
-			logExecutorWarning();
-		}
 
 		List<CallableProcessingInterceptor> interceptors = new ArrayList<>();
 		interceptors.add(webAsyncTask.getInterceptor());
@@ -357,26 +351,6 @@ public void startCallableProcessing(final WebAsyncTask<?> webAsyncTask, Object..
 		}
 	}
 
-	private void logExecutorWarning() {
-		if (taskExecutorWarning && logger.isWarnEnabled()) {
-			synchronized (DEFAULT_TASK_EXECUTOR) {
-				AsyncTaskExecutor executor = this.taskExecutor;
-				if (taskExecutorWarning &&
-						(executor instanceof SimpleAsyncTaskExecutor || executor instanceof SyncTaskExecutor)) {
-					String executorTypeName = executor.getClass().getSimpleName();
-					logger.warn("\n!!!\n" +
-							"An Executor is required to handle java.util.concurrent.Callable return values.\n" +
-							"Please, configure a TaskExecutor in the MVC config under \"async support\".\n" +
-							"The " + executorTypeName + " currently in use is not suitable under load.\n" +
-							"-------------------------------\n" +
-							"Request URI: '" + formatRequestUri() + "'\n" +
-							"!!!");
-					taskExecutorWarning = false;
-				}
-			}
-		}
-	}
-
 	private String formatRequestUri() {
 		HttpServletRequest request = this.asyncWebRequest.getNativeRequest(HttpServletRequest.class);
 		return request != null ? request.getRequestURI() : "servlet container";

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ReactiveTypeHandler.java

@@ -38,7 +38,6 @@
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
-import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.core.task.SyncTaskExecutor;
 import org.springframework.core.task.TaskExecutor;
 import org.springframework.http.MediaType;
@@ -91,8 +90,6 @@ class ReactiveTypeHandler {
 
 	private final ContentNegotiationManager contentNegotiationManager;
 
-	private boolean taskExecutorWarning;
-
 
 	public ReactiveTypeHandler() {
 		this(ReactiveAdapterRegistry.getSharedInstance(), new SyncTaskExecutor(), new ContentNegotiationManager());
@@ -105,9 +102,6 @@ public ReactiveTypeHandler() {
 		this.adapterRegistry = registry;
 		this.taskExecutor = executor;
 		this.contentNegotiationManager = manager;
-
-		this.taskExecutorWarning =
-				(executor instanceof SimpleAsyncTaskExecutor || executor instanceof SyncTaskExecutor);
 	}
 
 
@@ -147,20 +141,17 @@ public ResponseBodyEmitter handleValue(Object returnValue, MethodParameter retur
 		if (adapter.isMultiValue()) {
 			if (mediaTypes.stream().anyMatch(MediaType.TEXT_EVENT_STREAM::includes) ||
 					ServerSentEvent.class.isAssignableFrom(elementClass)) {
-				logExecutorWarning(returnType);
 				SseEmitter emitter = new SseEmitter(STREAMING_TIMEOUT_VALUE);
 				new SseEmitterSubscriber(emitter, this.taskExecutor).connect(adapter, returnValue);
 				return emitter;
 			}
 			if (CharSequence.class.isAssignableFrom(elementClass)) {
-				logExecutorWarning(returnType);
 				ResponseBodyEmitter emitter = getEmitter(mediaType.orElse(MediaType.TEXT_PLAIN));
 				new TextEmitterSubscriber(emitter, this.taskExecutor).connect(adapter, returnValue);
 				return emitter;
 			}
 			MediaType streamingResponseType = findConcreteStreamingMediaType(mediaTypes);
 			if (streamingResponseType != null) {
-				logExecutorWarning(returnType);
 				ResponseBodyEmitter emitter = getEmitter(streamingResponseType);
 				new JsonEmitterSubscriber(emitter, this.taskExecutor).connect(adapter, returnValue);
 				return emitter;
@@ -234,27 +225,6 @@ protected void extendResponse(ServerHttpResponse outputMessage) {
 		};
 	}
 
-	@SuppressWarnings("ConstantConditions")
-	private void logExecutorWarning(MethodParameter returnType) {
-		if (this.taskExecutorWarning && logger.isWarnEnabled()) {
-			synchronized (this) {
-				if (this.taskExecutorWarning) {
-					String executorTypeName = this.taskExecutor.getClass().getSimpleName();
-					logger.warn("\n!!!\n" +
-							"Streaming through a reactive type requires an Executor to write to the response.\n" +
-							"Please, configure a TaskExecutor in the MVC config under \"async support\".\n" +
-							"The " + executorTypeName + " currently in use is not suitable under load.\n" +
-							"-------------------------------\n" +
-							"Controller:\t" + returnType.getContainingClass().getName() + "\n" +
-							"Method:\t\t" + returnType.getMethod().getName() + "\n" +
-							"Returning:\t" + ResolvableType.forMethodParameter(returnType) + "\n" +
-							"!!!");
-					this.taskExecutorWarning = false;
-				}
-			}
-		}
-	}
-
 
 	private abstract static class AbstractEmitterSubscriber implements Subscriber<Object>, Runnable {
 

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerAdapter.java

@@ -169,7 +169,7 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 	@Nullable
 	private MethodValidator methodValidator;
 
-	private AsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor("MvcAsync");
+	private AsyncTaskExecutor taskExecutor = new MvcSimpleAsyncTaskExecutor();
 
 	@Nullable
 	private Long asyncRequestTimeout;
@@ -1041,4 +1041,37 @@ private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
 		return mav;
 	}
 
+
+	/**
+	 * A default Spring MVC AsyncTaskExecutor that warns if used.
+	 */
+	@SuppressWarnings("serial")
+	private class MvcSimpleAsyncTaskExecutor extends SimpleAsyncTaskExecutor {
+
+		private static Boolean taskExecutorWarning = true;
+
+		public MvcSimpleAsyncTaskExecutor() {
+			super("MvcAsync");
+		}
+
+		@Override
+		public void execute(Runnable task) {
+			if (taskExecutorWarning && logger.isWarnEnabled()) {
+				synchronized (this) {
+					if (taskExecutorWarning) {
+						logger.warn("""
+								!!!
+								Performing asynchronous handling through the default Spring MVC SimpleAsyncTaskExecutor.
+								This executor is not suitable for production use under load.
+								Please, configure an AsyncTaskExecutor through the WebMvc config.
+								-------------------------------
+								!!!""");
+						taskExecutorWarning = false;
+					}
+				}
+			}
+			super.execute(task);
+		}
+	}
+
 }