ResponseBodyResultHandler ignores ResponseEntity

Currently ResponseEntityResultHandler is ordered lower than
ResponseBodyResultHandler by default whch means a ResponseEntity
should not be picked by the ResponseBodyResultHandler.

However as it is easy to have both ResponseEntity and @ResponseBody
e.g. in @RestControler (or even by mistake) and in general it makes
sense for ResponseBodyResultHandler to explicitly recognize and
ignore the ResponseEntity return type.

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/method/annotation/ResponseBodyResultHandler.java

@@ -24,9 +24,9 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.core.convert.ConversionService;
+import org.springframework.http.HttpEntity;
 import org.springframework.http.converter.reactive.HttpMessageConverter;
 import org.springframework.web.bind.annotation.ResponseBody;
-import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.HandlerResultHandler;
 import org.springframework.web.reactive.accept.HeaderContentTypeResolver;
@@ -39,10 +39,10 @@ import org.springframework.web.server.ServerWebExchange;
  * with {@code @ResponseBody} writing to the body of the request or response with
  * an {@link HttpMessageConverter}.
  *
- * <p>By default the order for the result handler is set to 100. It detects the
- * presence of an {@code @ResponseBody} annotation and should be ordered after
- * result handlers that look for a specific return type such as
- * {@code ResponseEntity}.
+ * <p>By default the order for this result handler is set to 100. As it detects
+ * the presence of {@code @ResponseBody} it should be ordered after result
+ * handlers that look for a specific return type. Note however that this handler
+ * does recognize and explicitly ignores the {@code ResponseEntity} return type.
  *
  * @author Rossen Stoyanchev
  * @author Stephane Maldini
@@ -85,16 +85,36 @@ public class ResponseBodyResultHandler extends AbstractMessageConverterResultHan
 
 	@Override
 	public boolean supports(HandlerResult result) {
-		Object handler = result.getHandler();
-		if (handler instanceof HandlerMethod) {
-			MethodParameter returnType = ((HandlerMethod) handler).getReturnType();
-			Class<?> containingClass = returnType.getContainingClass();
-			return (AnnotationUtils.findAnnotation(containingClass, ResponseBody.class) != null ||
-					returnType.getMethodAnnotation(ResponseBody.class) != null);
+		ResolvableType returnType = result.getReturnValueType();
+		if (returnType.getSource() instanceof MethodParameter) {
+			MethodParameter parameter = (MethodParameter) returnType.getSource();
+			if (hasResponseBodyAnnotation(parameter) && !isHttpEntityType(returnType)) {
+				return true;
+			}
 		}
 		return false;
 	}
 
+	private boolean hasResponseBodyAnnotation(MethodParameter parameter) {
+		Class<?> containingClass = parameter.getContainingClass();
+		return (AnnotationUtils.findAnnotation(containingClass, ResponseBody.class) != null ||
+				parameter.getMethodAnnotation(ResponseBody.class) != null);
+	}
+
+	private boolean isHttpEntityType(ResolvableType returnType) {
+		if (HttpEntity.class.isAssignableFrom(returnType.getRawClass())) {
+			return true;
+		}
+		else if (getConversionService().canConvert(returnType.getRawClass(), Mono.class)) {
+			ResolvableType genericType = returnType.getGeneric(0);
+			if (HttpEntity.class.isAssignableFrom(genericType.getRawClass())) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+
 	@Override
 	public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {
 		Object body = result.getReturnValue().orElse(null);

spring-web-reactive/src/test/java/org/springframework/web/reactive/result/method/annotation/ResponseBodyResultHandlerTests.java

@@ -23,6 +23,7 @@ import java.util.List;
 
 import org.junit.Before;
 import org.junit.Test;
+import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.support.ByteBufferEncoder;
@@ -34,6 +35,7 @@ import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.core.convert.support.ReactiveStreamsToCompletableFutureConverter;
 import org.springframework.core.convert.support.ReactiveStreamsToRxJava1Converter;
 import org.springframework.http.HttpMethod;
+import org.springframework.http.ResponseEntity;
 import org.springframework.http.converter.reactive.CodecHttpMessageConverter;
 import org.springframework.http.converter.reactive.HttpMessageConverter;
 import org.springframework.http.converter.reactive.ResourceHttpMessageConverter;
@@ -108,14 +110,14 @@ public class ResponseBodyResultHandlerTests {
 
 	@Test
 	public void supports() throws NoSuchMethodException {
-		TestController controller = new TestController();
-		testSupports(controller, "handleReturningString", true);
-		testSupports(controller, "handleReturningVoid", true);
+		Object controller = new TestController();
+		testSupports(controller, "handleToString", true);
 		testSupports(controller, "doWork", false);
 
-		TestRestController restController = new TestRestController();
-		testSupports(restController, "handleReturningString", true);
-		testSupports(restController, "handleReturningVoid", true);
+		controller = new TestRestController();
+		testSupports(controller, "handleToString", true);
+		testSupports(controller, "handleToResponseEntity", false);
+		testSupports(controller, "handleToMonoResponseEntity", false);
 	}
 
 	private void testSupports(Object controller, String method, boolean result) throws NoSuchMethodException {
@@ -139,11 +141,15 @@ public class ResponseBodyResultHandlerTests {
 	@RestController @SuppressWarnings("unused")
 	private static class TestRestController {
 
-		public String handleReturningString() {
+		public String handleToString() {
 			return null;
 		}
 
-		public Void handleReturningVoid() {
+		public ResponseEntity<String> handleToResponseEntity() {
+			return null;
+		}
+
+		public Mono<ResponseEntity<String>> handleToMonoResponseEntity() {
 			return null;
 		}
 	}
@@ -152,12 +158,7 @@ public class ResponseBodyResultHandlerTests {
 	private static class TestController {
 
 		@ResponseBody
-		public String handleReturningString() {
-			return null;
-		}
-
-		@ResponseBody
-		public Void handleReturningVoid() {
+		public String handleToString() {
 			return null;
 		}