Revise @poller usage to single entry in Messaging Annotations.

Fixes spring-projects#3506

Author: onobc

spring-integration-core/src/main/java/org/springframework/integration/annotation/Aggregator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -105,10 +105,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/BridgeFrom.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -70,10 +70,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/BridgeTo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -77,10 +77,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/Filter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -128,10 +128,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/InboundChannelAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -23,6 +23,7 @@
 import java.lang.annotation.Target;
 
 import org.springframework.core.annotation.AliasFor;
+import org.springframework.messaging.handler.annotation.ValueConstants;
 
 /**
  * Indicates that a method is capable of producing a {@link org.springframework.messaging.Message}
@@ -86,10 +87,8 @@
 	/**
 	 * @return the {@link org.springframework.integration.annotation.Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
-	 * Only one {@link org.springframework.integration.annotation.Poller} element is allowed.
 	 * NOTE: a {@link Poller} here has {@link Poller#maxMessagesPerPoll()} set to 1 by default.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 }

spring-integration-core/src/main/java/org/springframework/integration/annotation/Router.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -151,10 +151,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/ServiceActivator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -121,11 +121,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
-	 * Only one {@link Poller} element is allowed.
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/Splitter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -116,10 +116,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/annotation/Transformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -92,10 +92,9 @@
 	/**
 	 * @return the {@link Poller} options for a polled endpoint
 	 * ({@link org.springframework.integration.scheduling.PollerMetadata}).
-	 * This attribute is an {@code array} just to allow an empty default (no poller).
 	 * Mutually exclusive with {@link #reactive()}.
 	 */
-	Poller[] poller() default { };
+	Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	/**
 	 * @return the {@link Reactive} marker for a consumer endpoint.

spring-integration-core/src/main/java/org/springframework/integration/config/annotation/AbstractMethodAnnotationPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 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.
@@ -363,24 +363,26 @@ protected AbstractEndpoint createEndpoint(MessageHandler handler, @SuppressWarni
 	protected AbstractEndpoint doCreateEndpoint(MessageHandler handler, MessageChannel inputChannel,
 			List<Annotation> annotations) {
 
-		Poller[] pollers = MessagingAnnotationUtils.resolveAttribute(annotations, "poller", Poller[].class);
+		Poller poller = MessagingAnnotationUtils.resolveAttribute(annotations, "poller", Poller.class);
+		boolean pollerProvided = poller != null && !ValueConstants.DEFAULT_NONE.equals(poller.value());
+
 		Reactive reactive = MessagingAnnotationUtils.resolveAttribute(annotations, "reactive", Reactive.class);
 		boolean reactiveProvided = reactive != null && !ValueConstants.DEFAULT_NONE.equals(reactive.value());
 
-		Assert.state(!reactiveProvided || ObjectUtils.isEmpty(pollers),
+		Assert.state(!reactiveProvided || !pollerProvided,
 				"The 'poller' and 'reactive' are mutually exclusive.");
 
 		if (inputChannel instanceof Publisher || handler instanceof ReactiveMessageHandlerAdapter || reactiveProvided) {
 			return reactiveStreamsConsumer(inputChannel, handler, reactiveProvided ? reactive : null);
 		}
 		else if (inputChannel instanceof SubscribableChannel) {
-			Assert.state(ObjectUtils.isEmpty(pollers), () ->
+			Assert.state(!pollerProvided, () ->
 					"A '@Poller' should not be specified for Annotation-based " +
 							"endpoint, since '" + inputChannel + "' is a SubscribableChannel (not pollable).");
 			return new EventDrivenConsumer((SubscribableChannel) inputChannel, handler);
 		}
 		else if (inputChannel instanceof PollableChannel) {
-			return pollingConsumer(inputChannel, handler, pollers);
+			return pollingConsumer(inputChannel, handler, poller);
 		}
 		else {
 			throw new IllegalArgumentException("Unsupported 'inputChannel' type: '"
@@ -414,19 +416,15 @@ private ReactiveStreamsConsumer reactiveStreamsConsumer(MessageChannel channel,
 		return reactiveStreamsConsumer;
 	}
 
-	private PollingConsumer pollingConsumer(MessageChannel inputChannel, MessageHandler handler, Poller[] pollers) {
+	private PollingConsumer pollingConsumer(MessageChannel inputChannel, MessageHandler handler, Poller poller) {
 		PollingConsumer pollingConsumer = new PollingConsumer((PollableChannel) inputChannel, handler);
-		configurePollingEndpoint(pollingConsumer, pollers);
+		configurePollingEndpoint(pollingConsumer, poller);
 		return pollingConsumer;
 	}
 
-	protected void configurePollingEndpoint(AbstractPollingEndpoint pollingEndpoint, Poller[] pollers) {
+	protected void configurePollingEndpoint(AbstractPollingEndpoint pollingEndpoint, Poller poller) {
 		PollerMetadata pollerMetadata;
-		if (!ObjectUtils.isEmpty(pollers)) {
-			Assert.state(pollers.length == 1,
-					"The 'poller' for an Annotation-based endpoint can have only one '@Poller'.");
-			Poller poller = pollers[0];
-
+		if (poller != null && !ValueConstants.DEFAULT_NONE.equals(poller.value())) {
 			String ref = poller.value();
 			String triggerRef = poller.trigger();
 			String executorRef = poller.taskExecutor();

spring-integration-core/src/main/java/org/springframework/integration/config/annotation/InboundChannelAdapterAnnotationPostProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -82,8 +82,8 @@ public Object postProcess(Object bean, String beanName, Method method, List<Anno
 		SourcePollingChannelAdapter adapter = new SourcePollingChannelAdapter();
 		adapter.setOutputChannelName(channelName);
 		adapter.setSource(messageSource);
-		Poller[] pollers = MessagingAnnotationUtils.resolveAttribute(annotations, "poller", Poller[].class);
-		configurePollingEndpoint(adapter, pollers);
+		Poller poller = MessagingAnnotationUtils.resolveAttribute(annotations, "poller", Poller.class);
+		configurePollingEndpoint(adapter, poller);
 
 		return adapter;
 	}

spring-integration-core/src/main/java/org/springframework/integration/util/MessagingAnnotationUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -26,12 +26,14 @@
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.integration.annotation.EndpointId;
 import org.springframework.integration.annotation.Payloads;
+import org.springframework.integration.annotation.Poller;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.handler.annotation.Header;
 import org.springframework.messaging.handler.annotation.Headers;
 import org.springframework.messaging.handler.annotation.Payload;
+import org.springframework.messaging.handler.annotation.ValueConstants;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.ReflectionUtils;
-import org.springframework.util.StringUtils;
 
 /**
  * Utility methods to support annotation processing.
@@ -41,17 +43,16 @@
  * @author Gunnar Hillert
  * @author Soby Chacko
  * @author Artem Bilan
+ * @author Chris Bono
  *
  * @since 4.0
  */
 public final class MessagingAnnotationUtils {
 
 	/**
-	 * Get the attribute value from the annotation hierarchy, returning the first non-empty
-	 * value closest to the annotated method. While traversing up the hierarchy, for string-valued
-	 * attributes, an empty string is ignored. For array-valued attributes, an empty
-	 * array is ignored.
-	 * The overridden attribute must be the same type.
+	 * Get the attribute value from the annotation hierarchy, returning the first
+	 * {@link MessagingAnnotationUtils#hasValue non-empty}) value closest to the annotated method.
+	 *
 	 * @param annotations The meta-annotations in order (closest first).
 	 * @param name The attribute name.
 	 * @param requiredType The expected type.
@@ -69,9 +70,31 @@ public static <T> T resolveAttribute(List<Annotation> annotations, String name,
 		return null;
 	}
 
-	public static boolean hasValue(Object value) {
-		return value != null && (!(value instanceof String) || (StringUtils.hasText((String) value))) // NOSONAR
-				&& (!value.getClass().isArray() || ((Object[]) value).length > 0);
+	/**
+	 * Determines if the value of a named attribute from an annotation instance contains an actual value.
+	 * <p>It is considered to NOT contain a value if it is null, an empty string, an empty array, or a {@link Poller}
+	 * whose 'value' field is set to {@link ValueConstants#DEFAULT_NONE}.
+	 *
+	 * @param annotationValue the value of the annotation attribute
+	 * @return whether {@code annotationValue} is set to a non-empty value
+	 */
+	public static boolean hasValue(Object annotationValue) {
+		if (annotationValue == null) {
+			return false;
+		}
+		// Empty array
+		if (ObjectUtils.isArray(annotationValue) && ObjectUtils.isEmpty(annotationValue)) {
+			return false;
+		}
+		// Empty string
+		if ((annotationValue instanceof String) && ObjectUtils.isEmpty(annotationValue)) {
+			return false;
+		}
+		// Poller with special 'none' value
+		if ((annotationValue instanceof Poller) && ValueConstants.DEFAULT_NONE.equals(((Poller) annotationValue).value())) {
+			return false;
+		}
+		return true;
 	}
 
 	public static Method findAnnotatedMethod(Object target, final Class<? extends Annotation> annotationType) {

spring-integration-core/src/test/java/org/springframework/integration/configuration/EnableIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 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.
@@ -127,6 +127,7 @@
 import org.springframework.messaging.MessageHandler;
 import org.springframework.messaging.PollableChannel;
 import org.springframework.messaging.handler.annotation.Payload;
+import org.springframework.messaging.handler.annotation.ValueConstants;
 import org.springframework.messaging.support.ChannelInterceptor;
 import org.springframework.messaging.support.GenericMessage;
 import org.springframework.scheduling.Trigger;
@@ -1506,7 +1507,7 @@ public interface TestGateway2 {
 
 		String phase() default "";
 
-		Poller[] poller() default { };
+		Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	}
 
@@ -1525,7 +1526,7 @@ public interface TestGateway2 {
 
 		String phase() default "";
 
-		Poller[] poller() default { };
+		Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	}
 
@@ -1631,7 +1632,7 @@ public interface TestGateway2 {
 
 		String phase() default "";
 
-		Poller[] poller() default { };
+		Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	}
 
@@ -1664,7 +1665,7 @@ public interface TestGateway2 {
 
 		String phase() default "";
 
-		Poller[] poller() default { };
+		Poller poller() default @Poller(ValueConstants.DEFAULT_NONE);
 
 	}