Add a ResolvableType field to HandlerResult

This change allows to be able to check generic type on the return value
at HandlerAdapter and ResultHandler level. For example, it allows to do
a Publisher<Void> check in SimpleHandlerResultHandler.

spring-web-reactive/src/main/java/org/springframework/reactive/web/dispatch/HandlerResult.java

@@ -16,6 +16,7 @@
 
 package org.springframework.reactive.web.dispatch;
 
+import org.springframework.core.ResolvableType;
 
 /**
  * Represent the result of the invocation of an handler.
@@ -28,10 +29,13 @@ public class HandlerResult {
 
 	private final Object value;
 
+	private final ResolvableType type;
 
-	public HandlerResult(Object handler, Object value) {
+
+	public HandlerResult(Object handler, Object value, ResolvableType type) {
 		this.handler = handler;
 		this.value = value;
+		this.type = type;
 	}
 
 
@@ -43,4 +47,7 @@ public class HandlerResult {
 		return this.value;
 	}
 
+	public ResolvableType getType() {
+		return type;
+	}
 }

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

@@ -22,6 +22,7 @@ import org.reactivestreams.Publisher;
 import reactor.Publishers;
 
 import org.springframework.core.Ordered;
+import org.springframework.core.ResolvableType;
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
 
@@ -32,6 +33,8 @@ import org.springframework.http.server.ReactiveServerHttpResponse;
  */
 public class SimpleHandlerResultHandler implements Ordered, HandlerResultHandler {
 
+	private static final ResolvableType PUBLISHER_VOID = ResolvableType.forClassWithGenerics(Publisher.class, Void.class);
+
 	private int order = Ordered.LOWEST_PRECEDENCE;
 
 
@@ -46,8 +49,8 @@ public class SimpleHandlerResultHandler implements Ordered, HandlerResultHandler
 
 	@Override
 	public boolean supports(HandlerResult result) {
-		Object value = result.getValue();
-		return value != null && Publisher.class.isAssignableFrom(value.getClass());
+		ResolvableType type = result.getType();
+		return type != null && PUBLISHER_VOID.isAssignableFrom(type);
 	}
 
 	@Override

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

@@ -19,6 +19,7 @@ package org.springframework.reactive.web.dispatch.handler;
 import org.reactivestreams.Publisher;
 import reactor.Publishers;
 
+import org.springframework.core.ResolvableType;
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
 import org.springframework.reactive.web.dispatch.HandlerAdapter;
@@ -38,6 +39,8 @@ import org.springframework.reactive.web.http.HttpHandler;
  */
 public class HttpHandlerAdapter implements HandlerAdapter {
 
+	private static final ResolvableType PUBLISHER_VOID = ResolvableType.forClassWithGenerics(Publisher.class, Void.class);
+
 
 	@Override
 	public boolean supports(Object handler) {
@@ -50,7 +53,7 @@ public class HttpHandlerAdapter implements HandlerAdapter {
 
 		HttpHandler httpHandler = (HttpHandler)handler;
 		Publisher<Void> completion = httpHandler.handle(request, response);
-		return Publishers.just(new HandlerResult(httpHandler, completion));
+		return Publishers.just(new HandlerResult(httpHandler, completion, PUBLISHER_VOID));
 	}
 
 }

spring-web-reactive/src/main/java/org/springframework/reactive/web/dispatch/method/annotation/RequestMappingHandlerAdapter.java

@@ -24,6 +24,7 @@ import org.reactivestreams.Publisher;
 import reactor.Publishers;
 
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.core.ResolvableType;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
@@ -91,9 +92,10 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 
 		InvocableHandlerMethod handlerMethod = new InvocableHandlerMethod((HandlerMethod) handler);
 		handlerMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
+		ResolvableType type =  ResolvableType.forMethodParameter(handlerMethod.getReturnType());
 
 		Publisher<Object> resultPublisher = handlerMethod.invokeForRequest(request);
-		return Publishers.map(resultPublisher, result -> new HandlerResult(handlerMethod, result));
+		return Publishers.map(resultPublisher, result -> new HandlerResult(handlerMethod, result, type));
 	}
 
 }

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

@@ -114,8 +114,7 @@ public class ResponseBodyResultHandler implements HandlerResultHandler, Ordered
 			return Publishers.empty();
 		}
 
-		HandlerMethod hm = (HandlerMethod) result.getHandler();
-		ResolvableType returnType = ResolvableType.forMethodParameter(hm.getReturnValueType(value));
+		ResolvableType returnType = result.getType();
 
 		List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request);
 		List<MediaType> producibleMediaTypes = getProducibleMediaTypes(returnType);