GH-1441: Fix Payload Detection with MessageHeaders

Resolves #1441

Previously, `MessageHeaders` had to be annotated with `@Headers` so that
it was ignored during payload parameter resolution; otherwise it caused
ambiguity.

Ignore `MessageHeaders` even when not so annotated.

Also fix some tests that were checking the same topic and count down latch so were
unconditionally passing.

Change one of those tests to verify the fix.

**cherry-pick to 2.4.x, 2.3.x**

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/adapter/MessagingMessageListenerAdapter.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.
@@ -34,6 +34,7 @@
 import org.springframework.core.MethodParameter;
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.handler.annotation.Header;
 import org.springframework.messaging.handler.annotation.Headers;
@@ -378,7 +379,8 @@ private Type determineInferredType() { // NOSONAR - complexity
 				 * We ignore parameters with type Message because they are not involved with conversion.
 				 */
 				boolean isHeaderOrHeaders = methodParameter.hasParameterAnnotation(Header.class)
-						|| methodParameter.hasParameterAnnotation(Headers.class);
+						|| methodParameter.hasParameterAnnotation(Headers.class)
+						|| methodParameter.getParameterType().equals(MessageHeaders.class);
 				boolean isPayload = methodParameter.hasParameterAnnotation(Payload.class);
 				if (isHeaderOrHeaders && isPayload && MessagingMessageListenerAdapter.this.logger.isWarnEnabled()) {
 					MessagingMessageListenerAdapter.this.logger.warn(this.method.getName()

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/annotation/EnableRabbitIntegrationTests.java

@@ -120,6 +120,7 @@
 import org.springframework.core.task.TaskExecutor;
 import org.springframework.data.web.JsonPath;
 import org.springframework.lang.NonNull;
+import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.converter.GenericMessageConverter;
 import org.springframework.messaging.handler.annotation.Header;
 import org.springframework.messaging.handler.annotation.Payload;
@@ -560,8 +561,9 @@ public void testRabbitHandlerNoDefaultValidationCount() throws InterruptedExcept
 	public void testDifferentTypes() throws InterruptedException {
 		Foo1 foo = new Foo1();
 		foo.setBar("bar");
+		this.service.foos.clear();
 		this.jsonRabbitTemplate.convertAndSend("differentTypes", foo);
-		assertThat(this.service.latch.await(10, TimeUnit.SECONDS)).isTrue();
+		assertThat(this.service.dtLatch1.await(10, TimeUnit.SECONDS)).isTrue();
 		assertThat(this.service.foos.get(0)).isInstanceOf(Foo2.class);
 		assertThat(((Foo2) this.service.foos.get(0)).getBar()).isEqualTo("bar");
 		assertThat(TestUtils.getPropertyValue(this.registry.getListenerContainer("different"), "concurrentConsumers")).isEqualTo(2);
@@ -571,8 +573,9 @@ public void testDifferentTypes() throws InterruptedException {
 	public void testDifferentTypesWithConcurrency() throws InterruptedException {
 		Foo1 foo = new Foo1();
 		foo.setBar("bar");
-		this.jsonRabbitTemplate.convertAndSend("differentTypes", foo);
-		assertThat(this.service.latch.await(10, TimeUnit.SECONDS)).isTrue();
+		this.service.foos.clear();
+		this.jsonRabbitTemplate.convertAndSend("differentTypes2", foo);
+		assertThat(this.service.dtLatch2.await(10, TimeUnit.SECONDS)).isTrue();
 		assertThat(this.service.foos.get(0)).isInstanceOf(Foo2.class);
 		assertThat(((Foo2) this.service.foos.get(0)).getBar()).isEqualTo("bar");
 		MessageListenerContainer container = this.registry.getListenerContainer("differentWithConcurrency");
@@ -584,8 +587,9 @@ public void testDifferentTypesWithConcurrency() throws InterruptedException {
 	public void testDifferentTypesWithVariableConcurrency() throws InterruptedException {
 		Foo1 foo = new Foo1();
 		foo.setBar("bar");
-		this.jsonRabbitTemplate.convertAndSend("differentTypes", foo);
-		assertThat(this.service.latch.await(10, TimeUnit.SECONDS)).isTrue();
+		this.service.foos.clear();
+		this.jsonRabbitTemplate.convertAndSend("differentTypes3", foo);
+		assertThat(this.service.dtLatch3.await(10, TimeUnit.SECONDS)).isTrue();
 		assertThat(this.service.foos.get(0)).isInstanceOf(Foo2.class);
 		assertThat(((Foo2) this.service.foos.get(0)).getBar()).isEqualTo("bar");
 		MessageListenerContainer container = this.registry.getListenerContainer("differentWithVariableConcurrency");
@@ -1086,7 +1090,11 @@ public static class MyService {
 
 		final List<Object> foos = new ArrayList<>();
 
-		final CountDownLatch latch = new CountDownLatch(1);
+		final CountDownLatch dtLatch1 = new CountDownLatch(1);
+
+		final CountDownLatch dtLatch2 = new CountDownLatch(1);
+
+		final CountDownLatch dtLatch3 = new CountDownLatch(1);
 
 		final CountDownLatch validationLatch = new CountDownLatch(1);
 
@@ -1237,21 +1245,21 @@ public void handleIt(Date body) {
 				containerFactory = "jsonListenerContainerFactoryNoClassMapper")
 		public void handleDifferent(@Validated Foo2 foo) {
 			foos.add(foo);
-			latch.countDown();
+			dtLatch1.countDown();
 		}
 
 		@RabbitListener(id = "differentWithConcurrency", queues = "differentTypes2",
-				containerFactory = "jsonListenerContainerFactory", concurrency = "#{3}")
-		public void handleDifferentWithConcurrency(Foo2 foo) {
+				containerFactory = "jsonListenerContainerFactoryNoClassMapper", concurrency = "#{3}")
+		public void handleDifferentWithConcurrency(Foo2 foo, MessageHeaders headers) {
 			foos.add(foo);
-			latch.countDown();
+			dtLatch2.countDown();
 		}
 
 		@RabbitListener(id = "differentWithVariableConcurrency", queues = "differentTypes3",
 				containerFactory = "jsonListenerContainerFactory", concurrency = "3-4")
 		public void handleDifferentWithVariableConcurrency(Foo2 foo) {
 			foos.add(foo);
-			latch.countDown();
+			dtLatch3.countDown();
 		}
 
 		@RabbitListener(id = "notStarted", containerFactory = "rabbitAutoStartFalseListenerContainerFactory",