Add support for MVC router functions to mappings endpoint

See gh-44163

Signed-off-by: puppy4c <puppy4c@foxmail.com>

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/documentation/MappingsEndpointServletDocumentationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2024 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -47,6 +47,9 @@ import org.springframework.restdocs.payload.ResponseFieldsSnippet;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.RouterFunctions;
+import org.springframework.web.servlet.function.ServerResponse;
 
 import static org.springframework.restdocs.payload.PayloadDocumentation.beneathPath;
 import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWithPath;
@@ -54,6 +57,7 @@ import static org.springframework.restdocs.payload.PayloadDocumentation.response
 import static org.springframework.restdocs.payload.PayloadDocumentation.subsectionWithPath;
 import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.document;
 import static org.springframework.restdocs.webtestclient.WebTestClientRestDocumentation.documentationConfiguration;
+import static org.springframework.web.servlet.function.RequestPredicates.GET;
 
 /**
  * Tests for generating documentation describing {@link MappingsEndpoint}.
@@ -130,6 +134,13 @@ class MappingsEndpointServletDocumentationTests extends AbstractEndpointDocument
 				fieldWithPath("*.[].details.handlerMethod.name").description("Name of the method."),
 				fieldWithPath("*.[].details.handlerMethod.descriptor")
 					.description("Descriptor of the method as specified in the Java Language Specification."));
+		List<FieldDescriptor> handlerFunction = List.of(
+				fieldWithPath("*.[].details.handlerFunction").optional()
+						.type(JsonFieldType.OBJECT)
+						.description("Details of the function, if any, that will handle requests to this mapping."),
+				fieldWithPath("*.[].details.handlerFunction.className").type(JsonFieldType.STRING)
+						.description("Fully qualified name of the class of the function."));
+		dispatcherServletFields.addAll(handlerFunction);
 		dispatcherServletFields.addAll(handlerMethod);
 		dispatcherServletFields.addAll(requestMappingConditions);
 		this.client.get()
@@ -192,6 +203,11 @@ class MappingsEndpointServletDocumentationTests extends AbstractEndpointDocument
 			return new ExampleController();
 		}
 
+		@Bean
+		RouterFunction<ServerResponse> exampleRouter() {
+			return RouterFunctions.route(GET("/foo"), (request) -> ServerResponse.ok().build());
+		}
+
 	}
 
 	@RestController

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/web/mappings/servlet/DispatcherServletMappingDetails.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -29,6 +29,8 @@ public class DispatcherServletMappingDetails {
 
 	private HandlerMethodDescription handlerMethod;
 
+	private HandlerFunctionDescription handlerFunction;
+
 	private RequestMappingConditionsDescription requestMappingConditions;
 
 	public HandlerMethodDescription getHandlerMethod() {
@@ -39,6 +41,14 @@ public class DispatcherServletMappingDetails {
 		this.handlerMethod = handlerMethod;
 	}
 
+	public HandlerFunctionDescription getHandlerFunction() {
+		return this.handlerFunction;
+	}
+
+	void setHandlerFunction(HandlerFunctionDescription handlerFunction) {
+		this.handlerFunction = handlerFunction;
+	}
+
 	public RequestMappingConditionsDescription getRequestMappingConditions() {
 		return this.requestMappingConditions;
 	}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/web/mappings/servlet/DispatcherServletsMappingDescriptionProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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 +23,8 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Optional;
+import java.util.function.Function;
 import java.util.stream.Stream;
 
 import jakarta.servlet.Servlet;
@@ -36,10 +38,17 @@ import org.springframework.boot.actuate.web.mappings.servlet.DispatcherServletsM
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.ImportRuntimeHints;
+import org.springframework.core.io.Resource;
 import org.springframework.web.context.WebApplicationContext;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.HandlerMapping;
+import org.springframework.web.servlet.function.HandlerFunction;
+import org.springframework.web.servlet.function.RequestPredicate;
+import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.RouterFunctions.Visitor;
+import org.springframework.web.servlet.function.ServerRequest;
+import org.springframework.web.servlet.function.support.RouterFunctionMapping;
 import org.springframework.web.servlet.handler.AbstractUrlHandlerMapping;
 import org.springframework.web.servlet.mvc.method.RequestMappingInfo;
 import org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping;
@@ -63,6 +72,7 @@ public class DispatcherServletsMappingDescriptionProvider implements MappingDesc
 		providers.add(new RequestMappingInfoHandlerMappingDescriptionProvider());
 		providers.add(new UrlHandlerMappingDescriptionProvider());
 		providers.add(new IterableDelegatesHandlerMappingDescriptionProvider(new ArrayList<>(providers)));
+		providers.add(new RouterFunctionMappingDescriptionProvider());
 		descriptionProviders = Collections.unmodifiableList(providers);
 	}
 
@@ -200,6 +210,62 @@ public class DispatcherServletsMappingDescriptionProvider implements MappingDesc
 
 	}
 
+	private static final class RouterFunctionMappingDescriptionProvider
+			implements HandlerMappingDescriptionProvider<RouterFunctionMapping> {
+
+		@Override
+		public Class<RouterFunctionMapping> getMappingClass() {
+			return RouterFunctionMapping.class;
+		}
+
+		@Override
+		public List<DispatcherServletMappingDescription> describe(RouterFunctionMapping handlerMapping) {
+			MappingDescriptionVisitor visitor = new MappingDescriptionVisitor();
+			RouterFunction<?> routerFunction = handlerMapping.getRouterFunction();
+			if (routerFunction != null) {
+				routerFunction.accept(visitor);
+			}
+			return visitor.descriptions;
+		}
+
+	}
+
+	private static final class MappingDescriptionVisitor implements Visitor {
+
+		private final List<DispatcherServletMappingDescription> descriptions = new ArrayList<>();
+
+		@Override
+		public void startNested(RequestPredicate predicate) {
+		}
+
+		@Override
+		public void endNested(RequestPredicate predicate) {
+		}
+
+		@Override
+		public void route(RequestPredicate predicate, HandlerFunction<?> handlerFunction) {
+			DispatcherServletMappingDetails details = new DispatcherServletMappingDetails();
+			details.setHandlerFunction(new HandlerFunctionDescription(handlerFunction));
+			this.descriptions.add(
+					new DispatcherServletMappingDescription(predicate.toString(), handlerFunction.toString(), details));
+		}
+
+		@Override
+		public void resources(Function<ServerRequest, Optional<Resource>> lookupFunction) {
+
+		}
+
+		@Override
+		public void attributes(Map<String, Object> attributes) {
+		}
+
+		@Override
+		public void unknown(RouterFunction<?> routerFunction) {
+
+		}
+
+	}
+
 	static class DispatcherServletsMappingDescriptionProviderRuntimeHints implements RuntimeHintsRegistrar {
 
 		private final BindingReflectionHintsRegistrar bindingRegistrar = new BindingReflectionHintsRegistrar();

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/web/mappings/servlet/HandlerFunctionDescription.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2012-2025 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.web.mappings.servlet;
+
+
+import org.springframework.web.servlet.function.HandlerFunction;
+
+/**
+ * Description of a {@link HandlerFunction}.
+ *
+ * @author Xiong Tang
+ * @since 3.5.0
+ */
+public class HandlerFunctionDescription {
+
+	private final String className;
+
+	HandlerFunctionDescription(HandlerFunction<?> handlerFunction) {
+		this.className = getHandlerFunctionClassName(handlerFunction);
+	}
+
+	private static String getHandlerFunctionClassName(HandlerFunction<?> handlerFunction) {
+		Class<?> functionClass = handlerFunction.getClass();
+		String canonicalName = functionClass.getCanonicalName();
+		return (canonicalName != null) ? canonicalName : functionClass.getName();
+	}
+
+	public String getClassName() {
+		return this.className;
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/web/mappings/MappingsEndpointTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -88,7 +88,7 @@ class MappingsEndpointTests {
 						"dispatcherServlets");
 				assertThat(dispatcherServlets).containsOnlyKeys("dispatcherServlet");
 				List<DispatcherServletMappingDescription> handlerMappings = dispatcherServlets.get("dispatcherServlet");
-				assertThat(handlerMappings).hasSize(1);
+				assertThat(handlerMappings).hasSize(3);
 				List<ServletRegistrationMappingDescription> servlets = mappings(contextMappings, "servlets");
 				assertThat(servlets).hasSize(1);
 				List<FilterRegistrationMappingDescription> filters = mappings(contextMappings, "servletFilters");
@@ -111,7 +111,7 @@ class MappingsEndpointTests {
 						"dispatcherServlets");
 				assertThat(dispatcherServlets).containsOnlyKeys("dispatcherServlet");
 				List<DispatcherServletMappingDescription> handlerMappings = dispatcherServlets.get("dispatcherServlet");
-				assertThat(handlerMappings).hasSize(1);
+				assertThat(handlerMappings).hasSize(3);
 				List<ServletRegistrationMappingDescription> servlets = mappings(contextMappings, "servlets");
 				assertThat(servlets).hasSize(1);
 				List<FilterRegistrationMappingDescription> filters = mappings(contextMappings, "servletFilters");
@@ -131,9 +131,9 @@ class MappingsEndpointTests {
 						"dispatcherServlets");
 				assertThat(dispatcherServlets).containsOnlyKeys("dispatcherServlet",
 						"customDispatcherServletRegistration", "anotherDispatcherServletRegistration");
-				assertThat(dispatcherServlets.get("dispatcherServlet")).hasSize(1);
-				assertThat(dispatcherServlets.get("customDispatcherServletRegistration")).hasSize(1);
-				assertThat(dispatcherServlets.get("anotherDispatcherServletRegistration")).hasSize(1);
+				assertThat(dispatcherServlets.get("dispatcherServlet")).hasSize(3);
+				assertThat(dispatcherServlets.get("customDispatcherServletRegistration")).hasSize(3);
+				assertThat(dispatcherServlets.get("anotherDispatcherServletRegistration")).hasSize(3);
 			});
 	}
 
@@ -253,6 +253,15 @@ class MappingsEndpointTests {
 
 		}
 
+		@Bean
+		org.springframework.web.servlet.function.RouterFunction<org.springframework.web.servlet.function.ServerResponse> routerFunction() {
+			return org.springframework.web.servlet.function.RouterFunctions
+					.route(org.springframework.web.servlet.function.RequestPredicates.GET("/one"),
+							(request) -> org.springframework.web.servlet.function.ServerResponse.ok().build())
+					.andRoute(org.springframework.web.servlet.function.RequestPredicates.POST("/two"),
+							(request) -> org.springframework.web.servlet.function.ServerResponse.ok().build());
+		}
+
 	}
 
 	@Configuration