Support handler methods returning void, Observable<Void>, etc.

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

@@ -23,22 +23,35 @@ import reactor.Publishers;
 
 import org.springframework.core.Ordered;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionService;
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
+import org.springframework.util.Assert;
 import org.springframework.web.reactive.HandlerResult;
 import org.springframework.web.reactive.HandlerResultHandler;
 
 /**
- * Supports {@link HandlerResult} with a {@code Publisher<Void>} value.
+ * Supports {@link HandlerResult} with a {@code void} or {@code Publisher<Void>} value.
+ * An optional {link ConversionService} can be used to support types that can be converted to
+ * {@code Publisher<Void>}, like {@code Observable<Void>} or {@code CompletableFuture<Void>}.
  *
  * @author Sebastien Deleuze
  */
 public class SimpleHandlerResultHandler implements Ordered, HandlerResultHandler {
 
-	private static final ResolvableType PUBLISHER_VOID = ResolvableType.forClassWithGenerics(Publisher.class, Void.class);
-
 	private int order = Ordered.LOWEST_PRECEDENCE;
 
+	private ConversionService conversionService;
+
+
+	public SimpleHandlerResultHandler() {
+	}
+
+	public SimpleHandlerResultHandler(ConversionService conversionService) {
+		Assert.notNull(conversionService, "'conversionService' is required.");
+		this.conversionService = conversionService;
+	}
+
 
 	public void setOrder(int order) {
 		this.order = order;
@@ -52,14 +65,24 @@ public class SimpleHandlerResultHandler implements Ordered, HandlerResultHandler
 	@Override
 	public boolean supports(HandlerResult result) {
 		ResolvableType type = result.getValueType();
-		return type != null && PUBLISHER_VOID.isAssignableFrom(type);
+		return type != null && Void.TYPE.equals(type.getRawClass()) ||
+				(Void.class.isAssignableFrom(type.getGeneric(0).getRawClass()) && isConvertibleToPublisher(type));
+	}
+
+	private boolean isConvertibleToPublisher(ResolvableType type) {
+		return Publisher.class.isAssignableFrom(type.getRawClass()) ||
+				((this.conversionService != null) && this.conversionService.canConvert(type.getRawClass(), Publisher.class));
 	}
 
 	@Override
 	public Publisher<Void> handleResult(ReactiveServerHttpRequest request,
 			ReactiveServerHttpResponse response, HandlerResult result) {
 
-		Publisher<Void> completion = Publishers.completable((Publisher<?>)result.getValue());
+		Object value = result.getValue();
+		if (Void.TYPE.equals(result.getValueType().getRawClass())) {
+			return response.writeHeaders();
+		}
+		Publisher<Void> completion = (value instanceof Publisher ? (Publisher<Void>)value : this.conversionService.convert(value, Publisher.class));
 		return Publishers.concat(Publishers.from(Arrays.asList(completion, response.writeHeaders())));
 	}
 }

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

@@ -16,12 +16,20 @@
 
 package org.springframework.web.reactive.handler;
 
+import java.util.concurrent.CompletableFuture;
+
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import org.junit.Test;
 import org.reactivestreams.Publisher;
+import reactor.rx.Stream;
+import rx.Observable;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.support.GenericConversionService;
+import org.springframework.core.convert.support.ReactiveStreamsToCompletableFutureConverter;
+import org.springframework.core.convert.support.ReactiveStreamsToReactorConverter;
+import org.springframework.core.convert.support.ReactiveStreamsToRxJava1Converter;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.HandlerResult;
 
@@ -38,8 +46,44 @@ public class SimpleHandlerResultHandlerTests {
 
 		HandlerMethod hm = new HandlerMethod(controller, TestController.class.getMethod("voidReturnValue"));
 		ResolvableType type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("publisherString"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
 		assertFalse(resultHandler.supports(new HandlerResult(hm, null, type)));
 
+		hm = new HandlerMethod(controller, TestController.class.getMethod("publisherVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("streamVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		// Reactor Stream is a Publisher
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("observableVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertFalse(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("completableFutureVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertFalse(resultHandler.supports(new HandlerResult(hm, null, type)));
+	}
+
+	@Test
+	public void supportsWithConversionService() throws NoSuchMethodException {
+
+		GenericConversionService conversionService = new GenericConversionService();
+		conversionService.addConverter(new ReactiveStreamsToCompletableFutureConverter());
+		conversionService.addConverter(new ReactiveStreamsToReactorConverter());
+		conversionService.addConverter(new ReactiveStreamsToRxJava1Converter());
+		SimpleHandlerResultHandler resultHandler = new SimpleHandlerResultHandler(conversionService);
+		TestController controller = new TestController();
+
+		HandlerMethod hm = new HandlerMethod(controller, TestController.class.getMethod("voidReturnValue"));
+		ResolvableType type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
 		hm = new HandlerMethod(controller, TestController.class.getMethod("publisherString"));
 		type = ResolvableType.forMethodParameter(hm.getReturnType());
 		assertFalse(resultHandler.supports(new HandlerResult(hm, null, type)));
@@ -47,14 +91,25 @@ public class SimpleHandlerResultHandlerTests {
 		hm = new HandlerMethod(controller, TestController.class.getMethod("publisherVoid"));
 		type = ResolvableType.forMethodParameter(hm.getReturnType());
 		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("streamVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("observableVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
+
+		hm = new HandlerMethod(controller, TestController.class.getMethod("completableFutureVoid"));
+		type = ResolvableType.forMethodParameter(hm.getReturnType());
+		assertTrue(resultHandler.supports(new HandlerResult(hm, null, type)));
 	}
 
 
 	@SuppressWarnings("unused")
 	private static class TestController {
 
-		public Publisher<String> voidReturnValue() {
-			return null;
+		public void voidReturnValue() {
 		}
 
 		public Publisher<String> publisherString() {
@@ -64,6 +119,18 @@ public class SimpleHandlerResultHandlerTests {
 		public Publisher<Void> publisherVoid() {
 			return null;
 		}
+
+		public Stream<Void> streamVoid() {
+			return null;
+		}
+
+		public Observable<Void> observableVoid() {
+			return null;
+		}
+
+		public CompletableFuture<Void> completableFutureVoid() {
+			return null;
+		}
 	}
 
 }

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

@@ -197,16 +197,18 @@ public class RequestMappingIntegrationTests extends AbstractHttpHandlerIntegrati
 	}
 
 	@Test
-	public void create() throws Exception {
-		RestTemplate restTemplate = new RestTemplate();
-		URI url = new URI("http://localhost:" + this.port + "/create");
-		RequestEntity<List<Person>> request = RequestEntity.post(url)
-				.contentType(MediaType.APPLICATION_JSON)
-				.body(Arrays.asList(new Person("Robert"), new Person("Marie")));
-		ResponseEntity<Void> response = restTemplate.exchange(request, Void.class);
+	public void publisherCreate() throws Exception {
+		create("http://localhost:" + this.port + "/publisher-create");
+	}
 
-		assertEquals(HttpStatus.OK, response.getStatusCode());
-		assertEquals(2, this.wac.getBean(TestController.class).persons.size());
+	@Test
+	public void streamCreate() throws Exception {
+		create("http://localhost:" + this.port + "/stream-create");
+	}
+
+	@Test
+	public void observableCreate() throws Exception {
+		create("http://localhost:" + this.port + "/observable-create");
 	}
 
 
@@ -259,6 +261,18 @@ public class RequestMappingIntegrationTests extends AbstractHttpHandlerIntegrati
 		assertEquals("MARIE", results.get(1).getName());
 	}
 
+	private void create(String requestUrl) throws Exception {
+		RestTemplate restTemplate = new RestTemplate();
+		URI url = new URI(requestUrl);
+		RequestEntity<List<Person>> request = RequestEntity.post(url)
+				.contentType(MediaType.APPLICATION_JSON)
+				.body(Arrays.asList(new Person("Robert"), new Person("Marie")));
+		ResponseEntity<Void> response = restTemplate.exchange(request, Void.class);
+
+		assertEquals(HttpStatus.OK, response.getStatusCode());
+		assertEquals(2, this.wac.getBean(TestController.class).persons.size());
+	}
+
 
 	@Configuration
 	@SuppressWarnings("unused")
@@ -295,7 +309,7 @@ public class RequestMappingIntegrationTests extends AbstractHttpHandlerIntegrati
 
 		@Bean
 		public SimpleHandlerResultHandler simpleHandlerResultHandler() {
-			return new SimpleHandlerResultHandler();
+			return new SimpleHandlerResultHandler(conversionService());
 		}
 
 	}
@@ -448,11 +462,21 @@ public class RequestMappingIntegrationTests extends AbstractHttpHandlerIntegrati
 			});
 		}
 
-		@RequestMapping("/create")
-		public Publisher<Void> create(@RequestBody Stream<Person> personStream) {
+		@RequestMapping("/publisher-create")
+		public Publisher<Void> publisherCreate(@RequestBody Publisher<Person> personStream) {
+			return Streams.wrap(personStream).toList().onSuccess(persons::addAll).after();
+		}
+
+		@RequestMapping("/stream-create")
+		public Promise<Void> streamCreate(@RequestBody Stream<Person> personStream) {
 			return personStream.toList().onSuccess(persons::addAll).after();
 		}
 
+		@RequestMapping("/observable-create")
+		public Observable<Void> observableCreate(@RequestBody Observable<Person> personStream) {
+			return personStream.toList().doOnNext(p -> persons.addAll(p)).flatMap(document -> Observable.empty());
+		}
+
 		//TODO add mixed and T request mappings tests
 
 	}