Reject mixed @⁠RequestMapping and @⁠HttpExchange declarations in MVC & WebFlux

This commit updates the RequestMappingHandlerMapping implementations in
Spring MVC and Spring WebFlux so that mixed @⁠RequestMapping and
@⁠HttpExchange declarations on the same element are rejected.

Note, however, that a @⁠Controller class which implements an interface
annotated with @⁠HttpExchange annotations can still inherit the
@⁠HttpExchange declarations from the interface or optionally override
them locally with @⁠HttpExchange or @⁠RequestMapping annotations.

See gh-31962
See gh-32049
Closes gh-32065

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerMappingTests.java

@@ -310,6 +310,40 @@ class RequestMappingHandlerMappingTests {
 				);
 	}
 
+	@Test  // gh-32065
+	void httpExchangeWithMixedAnnotationsAtClassLevel() throws NoSuchMethodException {
+		RequestMappingHandlerMapping mapping = createMapping();
+
+		Class<?> controllerClass = MixedClassLevelAnnotationsController.class;
+		Method method = controllerClass.getDeclaredMethod("post");
+
+		assertThatIllegalStateException()
+				.isThrownBy(() -> mapping.getMappingForMethod(method, controllerClass))
+				.withMessageContainingAll(
+					controllerClass.getName(),
+					"is annotated with @RequestMapping and @HttpExchange annotations, but only one is allowed:",
+					"@" + RequestMapping.class.getName(),
+					"@" + HttpExchange.class.getName()
+				);
+	}
+
+	@Test  // gh-32065
+	void httpExchangeWithMixedAnnotationsAtMethodLevel() throws NoSuchMethodException {
+		RequestMappingHandlerMapping mapping = createMapping();
+
+		Class<?> controllerClass = MixedMethodLevelAnnotationsController.class;
+		Method method = controllerClass.getDeclaredMethod("post");
+
+		assertThatIllegalStateException()
+				.isThrownBy(() -> mapping.getMappingForMethod(method, controllerClass))
+				.withMessageContainingAll(
+					method.toString(),
+					"is annotated with @RequestMapping and @HttpExchange annotations, but only one is allowed:",
+					"@" + PostMapping.class.getName(),
+					"@" + PostExchange.class.getName()
+				);
+	}
+
 	@SuppressWarnings("DataFlowIssue")
 	@Test
 	void httpExchangeWithDefaultValues() throws NoSuchMethodException {
@@ -488,6 +522,26 @@ class RequestMappingHandlerMappingTests {
 	}
 
 
+	@Controller
+	@RequestMapping("/api")
+	@HttpExchange("/api")
+	static class MixedClassLevelAnnotationsController {
+
+		@PostExchange("/post")
+		void post() {}
+	}
+
+
+	@Controller
+	@RequestMapping("/api")
+	static class MixedMethodLevelAnnotationsController {
+
+		@PostMapping("/post")
+		@PostExchange("/post")
+		void post() {}
+	}
+
+
 	@HttpExchange
 	@Target(ElementType.TYPE)
 	@Retention(RetentionPolicy.RUNTIME)