WebFluxResponseStatusExceptionHandler for @ResponseStatus introspection

The web.server package is quite low-level and should not depend on web.bind in order to avoid a dependency cycle. Extracting the introspection of the ResponseStatus annotation into a WebFlux-level subclass resolves the cycle.

Issue: SPR-16567

spring-webflux/src/main/java/org/springframework/web/reactive/config/WebFluxConfigurationSupport.java

@@ -52,6 +52,7 @@ import org.springframework.web.reactive.function.server.support.HandlerFunctionA
 import org.springframework.web.reactive.function.server.support.RouterFunctionMapping;
 import org.springframework.web.reactive.function.server.support.ServerResponseResultHandler;
 import org.springframework.web.reactive.handler.AbstractHandlerMapping;
+import org.springframework.web.reactive.handler.WebFluxResponseStatusExceptionHandler;
 import org.springframework.web.reactive.result.SimpleHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.ArgumentResolverConfigurer;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
@@ -62,7 +63,6 @@ import org.springframework.web.reactive.result.view.ViewResolutionResultHandler;
 import org.springframework.web.reactive.result.view.ViewResolver;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebExceptionHandler;
-import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
 import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
 import org.springframework.web.server.i18n.LocaleContextResolver;
 
@@ -108,7 +108,7 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 	@Bean
 	@Order(0)
 	public WebExceptionHandler responseStatusExceptionHandler() {
-		return new ResponseStatusExceptionHandler();
+		return new WebFluxResponseStatusExceptionHandler();
 	}
 
 	@Bean

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultHandlerStrategiesBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -25,10 +25,10 @@ import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.util.Assert;
+import org.springframework.web.reactive.handler.WebFluxResponseStatusExceptionHandler;
 import org.springframework.web.reactive.result.view.ViewResolver;
 import org.springframework.web.server.WebExceptionHandler;
 import org.springframework.web.server.WebFilter;
-import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
 import org.springframework.web.server.i18n.AcceptHeaderLocaleContextResolver;
 import org.springframework.web.server.i18n.LocaleContextResolver;
 
@@ -58,7 +58,7 @@ class DefaultHandlerStrategiesBuilder implements HandlerStrategies.Builder {
 
 	public void defaultConfiguration() {
 		this.codecConfigurer.registerDefaults(true);
-		this.exceptionHandlers.add(new ResponseStatusExceptionHandler());
+		this.exceptionHandlers.add(new WebFluxResponseStatusExceptionHandler());
 		this.localeContextResolver = new AcceptHeaderLocaleContextResolver();
 	}
 

spring-webflux/src/main/java/org/springframework/web/reactive/handler/WebFluxResponseStatusExceptionHandler.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2018 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
+ *
+ *      http://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.handler;
+
+import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.http.HttpStatus;
+import org.springframework.lang.Nullable;
+import org.springframework.web.bind.annotation.ResponseStatus;
+import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
+
+/**
+ * Common WebFlux exception handler that detects instances of
+ * {@link org.springframework.web.server.ResponseStatusException}
+ * (inherited from the base class) as well as exceptions annotated with
+ * {@link ResponseStatus @ResponseStatus} by determining the HTTP status
+ * for them and updating the status of the response accordingly.
+ *
+ * <p>If the response is already committed, the error remains unresolved
+ * and is propagated.
+ *
+ * @author Juergen Hoeller
+ * @author Rossen Stoyanchev
+ * @since 5.0.5
+ */
+public class WebFluxResponseStatusExceptionHandler extends ResponseStatusExceptionHandler {
+
+	@Override
+	@Nullable
+	protected HttpStatus determineStatus(Throwable ex) {
+		HttpStatus status = super.determineStatus(ex);
+		if (status == null) {
+			ResponseStatus ann = AnnotatedElementUtils.findMergedAnnotation(ex.getClass(), ResponseStatus.class);
+			if (ann != null) {
+				status = ann.code();
+			}
+		}
+		return status;
+	}
+
+}

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

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2002-2018 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
+ *
+ *      http://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.handler;
+
+import java.time.Duration;
+
+import org.junit.Test;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.web.bind.annotation.ResponseStatus;
+import org.springframework.web.reactive.handler.WebFluxResponseStatusExceptionHandler;
+import org.springframework.web.server.handler.ResponseStatusExceptionHandler;
+import org.springframework.web.server.handler.ResponseStatusExceptionHandlerTests;
+
+import static org.junit.Assert.*;
+
+/**
+ * Unit tests for {@link WebFluxResponseStatusExceptionHandler}.
+ *
+ * @author Juergen Hoeller
+ * @author Rossen Stoyanchev
+ */
+public class WebFluxResponseStatusExceptionHandlerTests extends ResponseStatusExceptionHandlerTests {
+
+	@Override
+	protected ResponseStatusExceptionHandler createResponseStatusExceptionHandler() {
+		return new WebFluxResponseStatusExceptionHandler();
+	}
+
+
+	@Test
+	public void handleAnnotatedException() {
+		Throwable ex = new CustomException();
+		this.handler.handle(this.exchange, ex).block(Duration.ofSeconds(5));
+		assertEquals(HttpStatus.I_AM_A_TEAPOT, this.exchange.getResponse().getStatusCode());
+	}
+
+	@Test
+	public void handleNestedAnnotatedException() {
+		Throwable ex = new Exception(new CustomException());
+		this.handler.handle(this.exchange, ex).block(Duration.ofSeconds(5));
+		assertEquals(HttpStatus.I_AM_A_TEAPOT, this.exchange.getResponse().getStatusCode());
+	}
+
+
+	@SuppressWarnings("serial")
+	@ResponseStatus(HttpStatus.I_AM_A_TEAPOT)
+	private static class CustomException extends Exception {
+	}
+
+}