DispatcherHandler maps errors to ResponseStatusException

The DispatcherHandler now has an errorMapper property that is a
function for transforming errors. By default this property is set to an
instance of DispatcherHandlerExceptionMapper which wraps "standard"
framework exceptions and @ResponseStatus-annotated exceptions as
ResponseStatusException.

This makes it easy to handle the exceptions downstream uniformly.

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

@@ -37,6 +37,7 @@ import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
+import org.springframework.web.ResponseStatusException;
 import org.springframework.http.server.reactive.ErrorHandlingHttpHandler;
 import org.springframework.http.server.reactive.FilterChainHttpHandler;
 import org.springframework.http.server.reactive.HttpExceptionHandler;
@@ -58,6 +59,7 @@ import org.springframework.web.reactive.method.annotation.ResponseBodyResultHand
 
 import static org.hamcrest.CoreMatchers.startsWith;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertThat;
 
@@ -101,7 +103,9 @@ public class DispatcherHandlerErrorTests {
 		Publisher<Void> publisher = this.dispatcherHandler.handle(this.request, this.response);
 		Throwable ex = awaitErrorSignal(publisher);
 
-		assertEquals(HandlerNotFoundException.class, ex.getClass());
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertNotNull(ex.getCause());
+		assertEquals(HandlerNotFoundException.class, ex.getCause().getClass());
 	}
 
 	@Test
@@ -155,7 +159,9 @@ public class DispatcherHandlerErrorTests {
 		Publisher<Void> publisher = this.dispatcherHandler.handle(this.request, this.response);
 		Throwable ex = awaitErrorSignal(publisher);
 
-		assertEquals(HttpMediaTypeNotAcceptableException.class, ex.getClass());
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertNotNull(ex.getCause());
+		assertEquals(HttpMediaTypeNotAcceptableException.class, ex.getCause().getClass());
 	}
 
 	@Test

spring-web-reactive/src/test/java/org/springframework/web/reactive/DispatcherHandlerExceptionMapperTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2002-2015 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;
+
+import java.util.Collections;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.HttpMediaTypeNotAcceptableException;
+import org.springframework.web.ResponseStatusException;
+import org.springframework.web.bind.annotation.ResponseStatus;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Rossen Stoyanchev
+ */
+public class DispatcherHandlerExceptionMapperTests {
+
+	private DispatcherHandlerExceptionMapper mapper;
+
+
+	@Before
+	public void setUp() throws Exception {
+		this.mapper = new DispatcherHandlerExceptionMapper();
+	}
+
+
+	@Test
+	public void handlerNotFound() throws Exception {
+		Throwable ex = new HandlerNotFoundException(HttpMethod.GET, "/path", new HttpHeaders());
+		ex = this.mapper.apply(ex);
+
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertEquals(HttpStatus.NOT_FOUND, ((ResponseStatusException) ex).getHttpStatus());
+	}
+
+
+	@Test
+	public void httpMediaTypeNotAcceptable() throws Exception {
+		Throwable ex = new HttpMediaTypeNotAcceptableException(Collections.emptyList());
+		ex = this.mapper.apply(ex);
+
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertEquals(HttpStatus.NOT_ACCEPTABLE, ((ResponseStatusException) ex).getHttpStatus());
+	}
+
+	@Test
+	public void responseStatusAnnotation() throws Exception {
+		Throwable ex = new ResponseStatusAnnotatedException();
+		ex = this.mapper.apply(ex);
+
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertEquals(HttpStatus.BAD_REQUEST, ((ResponseStatusException) ex).getHttpStatus());
+	}
+
+	@Test
+	public void responseStatusAnnotationOnRootCause() throws Exception {
+		Throwable ex = new Exception(new ResponseStatusAnnotatedException());
+		ex = this.mapper.apply(ex);
+
+		assertEquals(ResponseStatusException.class, ex.getClass());
+		assertEquals(HttpStatus.BAD_REQUEST, ((ResponseStatusException) ex).getHttpStatus());
+	}
+
+
+	@ResponseStatus(code = HttpStatus.BAD_REQUEST)
+	private static class ResponseStatusAnnotatedException extends Exception {
+	}
+
+}