Ensure handling of 404 errors for static resources

Closes gh-30930

spring-webflux/src/main/java/org/springframework/web/reactive/resource/NoResourceFoundException.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2002-2023 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.web.reactive.resource;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.server.ResponseStatusException;
+
+/**
+ * Raised when {@link ResourceWebHandler} is mapped to the request but can not
+ * find a matching resource.
+ *
+ * @author Rossen Stoyanchev
+ * @since 6.1
+ */
+@SuppressWarnings("serial")
+public class NoResourceFoundException extends ResponseStatusException {
+
+
+	public NoResourceFoundException(String resourcePath) {
+		super(HttpStatus.NOT_FOUND, "No static resource " + resourcePath + ".");
+		setDetail(getReason());
+	}
+
+}

spring-webflux/src/main/java/org/springframework/web/reactive/resource/ResourceWebHandler.java

@@ -41,7 +41,6 @@ import org.springframework.core.log.LogFormatUtils;
 import org.springframework.http.CacheControl;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
-import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.MediaTypeFactory;
 import org.springframework.http.codec.ResourceHttpMessageWriter;
@@ -54,7 +53,6 @@ import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.reactive.HandlerMapping;
 import org.springframework.web.server.MethodNotAllowedException;
-import org.springframework.web.server.ResponseStatusException;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebHandler;
 import org.springframework.web.util.pattern.PathPattern;
@@ -403,7 +401,7 @@ public class ResourceWebHandler implements WebHandler, InitializingBean {
 		return getResource(exchange)
 				.switchIfEmpty(Mono.defer(() -> {
 					logger.debug(exchange.getLogPrefix() + "Resource not found");
-					return Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND));
+					return Mono.error(new NoResourceFoundException(getResourcePath(exchange)));
 				}))
 				.flatMap(resource -> {
 					try {

spring-webflux/src/test/java/org/springframework/web/reactive/DispatcherHandlerErrorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -19,6 +19,7 @@ package org.springframework.web.reactive;
 import java.time.Duration;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.jupiter.api.BeforeEach;
@@ -32,15 +33,23 @@ import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
 import org.springframework.http.codec.EncoderHttpMessageWriter;
+import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.ControllerAdvice;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.reactive.accept.HeaderContentTypeResolver;
+import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
+import org.springframework.web.reactive.resource.ResourceWebHandler;
+import org.springframework.web.reactive.result.SimpleHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
 import org.springframework.web.reactive.result.method.annotation.ResponseBodyResultHandler;
+import org.springframework.web.reactive.result.method.annotation.ResponseEntityExceptionHandler;
+import org.springframework.web.reactive.result.method.annotation.ResponseEntityResultHandler;
 import org.springframework.web.server.NotAcceptableStatusException;
 import org.springframework.web.server.ResponseStatusException;
 import org.springframework.web.server.ServerWebExchange;
@@ -48,6 +57,7 @@ import org.springframework.web.server.WebExceptionHandler;
 import org.springframework.web.server.WebHandler;
 import org.springframework.web.server.handler.ExceptionHandlingWebHandler;
 import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRequest;
+import org.springframework.web.testfixture.http.server.reactive.MockServerHttpResponse;
 import org.springframework.web.testfixture.server.MockServerWebExchange;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -69,10 +79,11 @@ public class DispatcherHandlerErrorTests {
 
 	@BeforeEach
 	public void setup() {
-		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
-		ctx.register(TestConfig.class);
-		ctx.refresh();
-		this.dispatcherHandler = new DispatcherHandler(ctx);
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.register(TestConfig.class);
+		context.refresh();
+
+		this.dispatcherHandler = new DispatcherHandler(context);
 	}
 
 
@@ -94,6 +105,28 @@ public class DispatcherHandlerErrorTests {
 		StepVerifier.create(mono).consumeErrorWith(ex -> assertThat(ex).isNotSameAs(exceptionRef.get())).verify();
 	}
 
+	@Test
+	public void noStaticResource() {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.register(StaticResourceConfig.class);
+		context.refresh();
+
+		MockServerHttpRequest request = MockServerHttpRequest.get("/resources/non-existing").build();
+		MockServerWebExchange exchange = MockServerWebExchange.from(request);
+		new DispatcherHandler(context).handle(exchange).block();
+
+		MockServerHttpResponse response = exchange.getResponse();
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.NOT_FOUND);
+		assertThat(response.getHeaders().getContentType()).isEqualTo(MediaType.APPLICATION_PROBLEM_JSON);
+		assertThat(response.getBodyAsString().block()).isEqualTo("""
+				{"type":"about:blank",\
+				"title":"Not Found",\
+				"status":404,\
+				"detail":"No static resource non-existing.",\
+				"instance":"/resources/non-existing"}\
+				""");
+	}
+
 	@Test
 	public void controllerReturnsMonoError() {
 		MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get("/error-signal"));
@@ -223,6 +256,50 @@ public class DispatcherHandlerErrorTests {
 	}
 
 
+	@Configuration
+	@SuppressWarnings({"unused", "WeakerAccess"})
+	static class StaticResourceConfig {
+
+		@Bean
+		public SimpleUrlHandlerMapping resourceMapping(ResourceWebHandler resourceWebHandler) {
+			SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
+			mapping.setUrlMap(Map.of("/resources/**", resourceWebHandler));
+			return mapping;
+		}
+
+		@Bean
+		public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
+			return new RequestMappingHandlerAdapter();
+		}
+
+		@Bean
+		public SimpleHandlerAdapter simpleHandlerAdapter() {
+			return new SimpleHandlerAdapter();
+		}
+
+		@Bean
+		public ResourceWebHandler resourceWebHandler() {
+			return new ResourceWebHandler();
+		}
+
+		@Bean
+		public ResponseEntityResultHandler responseEntityResultHandler() {
+			ServerCodecConfigurer configurer = ServerCodecConfigurer.create();
+			return new ResponseEntityResultHandler(configurer.getWriters(), new HeaderContentTypeResolver());
+		}
+
+		@Bean
+		GlobalExceptionHandler globalExceptionHandler() {
+			return new GlobalExceptionHandler();
+		}
+	}
+
+
+	@ControllerAdvice
+	private static class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
+	}
+
+
 	private static class ServerError500ExceptionHandler implements WebExceptionHandler {
 
 		@Override