HandlerAdapter is asynchronous again

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

@@ -108,21 +108,21 @@ public class DispatcherHandler implements HttpHandler, ApplicationContextAware {
 		}
 
 		HandlerAdapter handlerAdapter = getHandlerAdapter(handler);
+		if (handlerAdapter == null) {
+			return Publishers.error(new IllegalStateException("No HandlerAdapter for " + handler));
+		}
 
-		try {
-			HandlerResult result = handlerAdapter.handle(request, response, handler);
+		Publisher<HandlerResult> resultPublisher = handlerAdapter.handle(request, response, handler);
+
+		return Publishers.concatMap(resultPublisher, result -> {
 			for (HandlerResultHandler resultHandler : resultHandlers) {
 				if (resultHandler.supports(result)) {
 					return resultHandler.handleResult(request, response, result);
 				}
 			}
 			return Publishers.error(new IllegalStateException(
-			  "No HandlerResultHandler for " + result.getValue()));
-		}
-		catch(Exception ex) {
-			return Publishers.error(ex);
-		}
-
+					"No HandlerResultHandler for " + result.getValue()));
+		});
 	}
 
 	protected Object getHandler(ReactiveServerHttpRequest request) {
@@ -142,8 +142,7 @@ public class DispatcherHandler implements HttpHandler, ApplicationContextAware {
 				return handlerAdapter;
 			}
 		}
-		// more specific exception
-		throw new IllegalStateException("No HandlerAdapter for " + handler);
+		return null;
 	}
 
 }

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

@@ -16,6 +16,8 @@
 
 package org.springframework.reactive.web.dispatch;
 
+import org.reactivestreams.Publisher;
+
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
 
@@ -53,6 +55,7 @@ public interface HandlerAdapter {
 	 * @throws Exception in case of errors
 	 * @return An {@link HandlerResult} instance
 	 */
-	HandlerResult handle(ReactiveServerHttpRequest request, ReactiveServerHttpResponse response, Object handler) throws Exception;
+	Publisher<HandlerResult> handle(ReactiveServerHttpRequest request,
+			ReactiveServerHttpResponse response, Object handler);
 
 }

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

@@ -17,6 +17,7 @@
 package org.springframework.reactive.web.dispatch.handler;
 
 import org.reactivestreams.Publisher;
+import reactor.Publishers;
 
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
@@ -44,10 +45,12 @@ public class HttpHandlerAdapter implements HandlerAdapter {
 	}
 
 	@Override
-	public HandlerResult handle(ReactiveServerHttpRequest request, ReactiveServerHttpResponse response, Object handler) {
+	public Publisher<HandlerResult> handle(ReactiveServerHttpRequest request,
+			ReactiveServerHttpResponse response, Object handler) {
+
 		HttpHandler httpHandler = (HttpHandler)handler;
 		Publisher<Void> completion = httpHandler.handle(request, response);
-		return new HandlerResult(httpHandler, completion);
+		return Publishers.just(new HandlerResult(httpHandler, completion));
 	}
 
 }

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

@@ -21,6 +21,9 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
+import org.reactivestreams.Publisher;
+import reactor.Publishers;
+
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.http.server.ReactiveServerHttpRequest;
 import org.springframework.http.server.ReactiveServerHttpResponse;
@@ -70,15 +73,20 @@ public class RequestMappingHandlerAdapter implements HandlerAdapter, Initializin
 	}
 
 	@Override
-	public HandlerResult handle(ReactiveServerHttpRequest request, ReactiveServerHttpResponse response,
-			Object handler) throws Exception {
+	public Publisher<HandlerResult> handle(ReactiveServerHttpRequest request,
+			ReactiveServerHttpResponse response, Object handler) {
 
-		final InvocableHandlerMethod invocable = new InvocableHandlerMethod((HandlerMethod) handler);
-		invocable.setHandlerMethodArgumentResolvers(this.argumentResolvers);
+		InvocableHandlerMethod handlerMethod = new InvocableHandlerMethod((HandlerMethod) handler);
+		handlerMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
 
-		Object result = invocable.invokeForRequest(request);
-
-		return new HandlerResult(invocable, result);
+		try {
+			Object result = handlerMethod.invokeForRequest(request);
+			return Publishers.just(new HandlerResult(handlerMethod, result));
+		}
+		catch (Exception e) {
+			// TODO: remove throws declaration from InvocableHandlerMethod
+			return Publishers.error(e);
+		}
 	}
 
-}
+}