Using WebAsyncManager in WebMvc.fn

This commit removed the existing code for dealing with asynchronous
results, and replaced it with code using the WebAsyncManager.

Closes gh-25931

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupport.java

@@ -682,7 +682,14 @@ public class WebMvcConfigurationSupport implements ApplicationContextAware, Serv
 	 */
 	@Bean
 	public HandlerFunctionAdapter handlerFunctionAdapter() {
-		return new HandlerFunctionAdapter();
+		HandlerFunctionAdapter adapter = new HandlerFunctionAdapter();
+
+		AsyncSupportConfigurer configurer = new AsyncSupportConfigurer();
+		configureAsyncSupport(configurer);
+		if (configurer.getTimeout() != null) {
+			adapter.setAsyncRequestTimeout(configurer.getTimeout());
+		}
+		return adapter;
 	}
 
 	/**

spring-webmvc/src/main/java/org/springframework/web/servlet/function/AsyncServerResponse.java

@@ -17,19 +17,14 @@
 package org.springframework.web.servlet.function;
 
 import java.io.IOException;
+import java.time.Duration;
 import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.CompletionException;
 import java.util.function.Function;
 
-import javax.servlet.AsyncContext;
-import javax.servlet.AsyncListener;
-import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
-import javax.servlet.ServletRequest;
-import javax.servlet.ServletResponse;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletRequest;
-import javax.servlet.http.HttpServletRequestWrapper;
 import javax.servlet.http.HttpServletResponse;
 
 import org.reactivestreams.Publisher;
@@ -42,6 +37,10 @@ import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.MultiValueMap;
+import org.springframework.web.context.request.async.AsyncWebRequest;
+import org.springframework.web.context.request.async.DeferredResult;
+import org.springframework.web.context.request.async.WebAsyncManager;
+import org.springframework.web.context.request.async.WebAsyncUtils;
 import org.springframework.web.servlet.ModelAndView;
 
 /**
@@ -59,9 +58,13 @@ final class AsyncServerResponse extends ErrorHandlingServerResponse {
 
 	private final CompletableFuture<ServerResponse> futureResponse;
 
+	@Nullable
+	private final Duration timeout;
 
-	private AsyncServerResponse(CompletableFuture<ServerResponse> futureResponse) {
+
+	private AsyncServerResponse(CompletableFuture<ServerResponse> futureResponse, @Nullable Duration timeout) {
 		this.futureResponse = futureResponse;
+		this.timeout = timeout;
 	}
 
 	@Override
@@ -96,44 +99,62 @@ final class AsyncServerResponse extends ErrorHandlingServerResponse {
 
 	@Nullable
 	@Override
-	public ModelAndView writeTo(HttpServletRequest request, HttpServletResponse response, Context context) {
+	public ModelAndView writeTo(HttpServletRequest request, HttpServletResponse response, Context context)
+			throws ServletException, IOException {
 
-		SharedAsyncContextHttpServletRequest sharedRequest = new SharedAsyncContextHttpServletRequest(request);
-		AsyncContext asyncContext = sharedRequest.startAsync(request, response);
-		this.futureResponse.whenComplete((futureResponse, futureThrowable) -> {
-			try {
-				if (futureResponse != null) {
-					ModelAndView mav = futureResponse.writeTo(sharedRequest, response, context);
-					Assert.state(mav == null, "Asynchronous, rendering ServerResponse implementations are not " +
-							"supported in WebMvc.fn. Please use WebFlux.fn instead.");
-				}
-				else if (futureThrowable != null) {
-					handleError(futureThrowable, request, response, context);
-				}
-			}
-			catch (Throwable throwable) {
-				try {
-					handleError(throwable, request, response, context);
-				}
-				catch (ServletException | IOException ex) {
-					logger.warn("Asynchronous execution resulted in exception", ex);
-				}
-			}
-			finally {
-				asyncContext.complete();
-			}
-		});
+		writeAsync(request, response, createDeferredResult());
 		return null;
 	}
 
+	static void writeAsync(HttpServletRequest request, HttpServletResponse response, DeferredResult<?> deferredResult)
+			throws ServletException, IOException {
+
+		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
+		AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
+		asyncManager.setAsyncWebRequest(asyncWebRequest);
+		try {
+			asyncManager.startDeferredResultProcessing(deferredResult);
+		}
+		catch (IOException | ServletException ex) {
+			throw ex;
+		}
+		catch (Exception ex) {
+			throw new ServletException("Async processing failed", ex);
+		}
+
+	}
+
+	private DeferredResult<ServerResponse> createDeferredResult() {
+		DeferredResult<ServerResponse> result;
+		if (this.timeout != null) {
+			result = new DeferredResult<>(this.timeout.toMillis());
+		}
+		else {
+			result = new DeferredResult<>();
+		}
+		this.futureResponse.handle((value, ex) -> {
+			if (ex != null) {
+				if (ex instanceof CompletionException && ex.getCause() != null) {
+					ex = ex.getCause();
+				}
+				result.setErrorResult(ex);
+			}
+			else {
+				result.setResult(value);
+			}
+			return null;
+		});
+		return result;
+	}
+
 
 	@SuppressWarnings({"unchecked"})
-	public static ServerResponse create(Object o) {
+	public static ServerResponse create(Object o, @Nullable Duration timeout) {
 		Assert.notNull(o, "Argument to async must not be null");
 
 		if (o instanceof CompletableFuture) {
 			CompletableFuture<ServerResponse> futureResponse = (CompletableFuture<ServerResponse>) o;
-			return new AsyncServerResponse(futureResponse);
+			return new AsyncServerResponse(futureResponse, timeout);
 		}
 		else if (reactiveStreamsPresent) {
 			ReactiveAdapterRegistry registry = ReactiveAdapterRegistry.getSharedInstance();
@@ -144,7 +165,7 @@ final class AsyncServerResponse extends ErrorHandlingServerResponse {
 				if (futureAdapter != null) {
 					CompletableFuture<ServerResponse> futureResponse =
 							(CompletableFuture<ServerResponse>) futureAdapter.fromPublisher(publisher);
-					return new AsyncServerResponse(futureResponse);
+					return new AsyncServerResponse(futureResponse, timeout);
 				}
 			}
 		}
@@ -152,150 +173,4 @@ final class AsyncServerResponse extends ErrorHandlingServerResponse {
 	}
 
 
-	/**
-	 * HttpServletRequestWrapper that shares its AsyncContext between this
-	 * AsyncServerResponse class and other, subsequent ServerResponse
-	 * implementations, keeping track of how many contexts where
-	 * started with startAsync(). This way, we make sure that
-	 * {@link AsyncContext#complete()} only completes for the response that
-	 * finishes last, and is not closed prematurely.
-	 */
-	private static final class SharedAsyncContextHttpServletRequest extends HttpServletRequestWrapper {
-
-		private final AsyncContext asyncContext;
-
-		private final AtomicInteger startedContexts;
-
-		public SharedAsyncContextHttpServletRequest(HttpServletRequest request) {
-			super(request);
-			this.asyncContext = request.startAsync();
-			this.startedContexts = new AtomicInteger(0);
-		}
-
-		private SharedAsyncContextHttpServletRequest(HttpServletRequest request, AsyncContext asyncContext,
-				AtomicInteger startedContexts) {
-			super(request);
-			this.asyncContext = asyncContext;
-			this.startedContexts = startedContexts;
-		}
-
-		@Override
-		public AsyncContext startAsync() throws IllegalStateException {
-			this.startedContexts.incrementAndGet();
-			return new SharedAsyncContext(this.asyncContext, this, this.asyncContext.getResponse(),
-					this.startedContexts);
-		}
-
-		@Override
-		public AsyncContext startAsync(ServletRequest servletRequest, ServletResponse servletResponse)
-				throws IllegalStateException {
-			this.startedContexts.incrementAndGet();
-			SharedAsyncContextHttpServletRequest sharedRequest;
-			if (servletRequest instanceof SharedAsyncContextHttpServletRequest) {
-				sharedRequest = (SharedAsyncContextHttpServletRequest) servletRequest;
-			}
-			else {
-				sharedRequest = new SharedAsyncContextHttpServletRequest((HttpServletRequest) servletRequest,
-						this.asyncContext, this.startedContexts);
-			}
-			return new SharedAsyncContext(this.asyncContext, sharedRequest, servletResponse, this.startedContexts);
-		}
-
-		@Override
-		public AsyncContext getAsyncContext() {
-			return new SharedAsyncContext(this.asyncContext, this, this.asyncContext.getResponse(), this.startedContexts);
-		}
-
-
-		private static final class SharedAsyncContext implements AsyncContext {
-
-			private final AsyncContext delegate;
-
-			private final AtomicInteger openContexts;
-
-			private final ServletRequest request;
-
-			private final ServletResponse response;
-
-
-			public SharedAsyncContext(AsyncContext delegate, SharedAsyncContextHttpServletRequest request,
-					ServletResponse response, AtomicInteger usageCount) {
-
-				this.delegate = delegate;
-				this.request = request;
-				this.response = response;
-				this.openContexts = usageCount;
-			}
-
-			@Override
-			public void complete() {
-				if (this.openContexts.decrementAndGet() == 0) {
-					this.delegate.complete();
-				}
-			}
-
-			@Override
-			public ServletRequest getRequest() {
-				return this.request;
-			}
-
-			@Override
-			public ServletResponse getResponse() {
-				return this.response;
-			}
-
-			@Override
-			public boolean hasOriginalRequestAndResponse() {
-				return this.delegate.hasOriginalRequestAndResponse();
-			}
-
-			@Override
-			public void dispatch() {
-				this.delegate.dispatch();
-			}
-
-			@Override
-			public void dispatch(String path) {
-				this.delegate.dispatch(path);
-			}
-
-			@Override
-			public void dispatch(ServletContext context, String path) {
-				this.delegate.dispatch(context, path);
-			}
-
-			@Override
-			public void start(Runnable run) {
-				this.delegate.start(run);
-			}
-
-			@Override
-			public void addListener(AsyncListener listener) {
-				this.delegate.addListener(listener);
-			}
-
-			@Override
-			public void addListener(AsyncListener listener,
-					ServletRequest servletRequest,
-					ServletResponse servletResponse) {
-
-				this.delegate.addListener(listener, servletRequest, servletResponse);
-			}
-
-			@Override
-			public <T extends AsyncListener> T createListener(Class<T> clazz) throws ServletException {
-				return this.delegate.createListener(clazz);
-			}
-
-			@Override
-			public void setTimeout(long timeout) {
-				this.delegate.setTimeout(timeout);
-			}
-
-			@Override
-			public long getTimeout() {
-				return this.delegate.getTimeout();
-			}
-		}
-	}
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/function/DefaultEntityResponseBuilder.java

@@ -25,11 +25,11 @@ import java.util.Arrays;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.concurrent.CompletionException;
 import java.util.concurrent.CompletionStage;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 
-import javax.servlet.AsyncContext;
 import javax.servlet.ServletException;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletRequest;
@@ -61,6 +61,7 @@ import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.HttpMediaTypeNotAcceptableException;
+import org.springframework.web.context.request.async.DeferredResult;
 import org.springframework.web.servlet.ModelAndView;
 
 /**
@@ -358,32 +359,39 @@ final class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T>
 		}
 
 		@Override
-		protected ModelAndView writeToInternal(HttpServletRequest servletRequest,
-				HttpServletResponse servletResponse, Context context) {
+		protected ModelAndView writeToInternal(HttpServletRequest servletRequest, HttpServletResponse servletResponse,
+				Context context) throws ServletException, IOException {
 
-			AsyncContext asyncContext = servletRequest.startAsync(servletRequest, servletResponse);
-			entity().whenComplete((entity, throwable) -> {
-				try {
-					if (entity != null) {
-
-						tryWriteEntityWithMessageConverters(entity,
-								(HttpServletRequest) asyncContext.getRequest(),
-								(HttpServletResponse) asyncContext.getResponse(),
-								context);
-					}
-					else if (throwable != null) {
-						handleError(throwable, servletRequest, servletResponse, context);
-					}
-				}
-				catch (ServletException | IOException ex) {
-					logger.warn("Asynchronous execution resulted in exception", ex);
-				}
-				finally {
-					asyncContext.complete();
-				}
-			});
+			DeferredResult<?> deferredResult = createDeferredResult(servletRequest, servletResponse, context);
+			AsyncServerResponse.writeAsync(servletRequest, servletResponse, deferredResult);
 			return null;
 		}
+
+		private DeferredResult<?> createDeferredResult(HttpServletRequest request, HttpServletResponse response,
+				Context context) {
+
+			DeferredResult<?> result = new DeferredResult<>();
+			entity().handle((value, ex) -> {
+				if (ex != null) {
+					if (ex instanceof CompletionException && ex.getCause() != null) {
+						ex = ex.getCause();
+					}
+					result.setErrorResult(ex);
+				}
+				else {
+					try {
+						tryWriteEntityWithMessageConverters(value, request, response, context);
+						result.setResult(null);
+					}
+					catch (ServletException | IOException writeException) {
+						result.setErrorResult(writeException);
+					}
+				}
+				return null;
+			});
+			return result;
+		}
+
 	}
 
 
@@ -399,35 +407,46 @@ final class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T>
 		}
 
 		@Override
-		protected ModelAndView writeToInternal(HttpServletRequest servletRequest,
-				HttpServletResponse servletResponse, Context context) {
+		protected ModelAndView writeToInternal(HttpServletRequest servletRequest, HttpServletResponse servletResponse,
+				Context context) throws ServletException, IOException {
 
-			AsyncContext asyncContext = servletRequest.startAsync(servletRequest,
-					new NoContentLengthResponseWrapper(servletResponse));
-			entity().subscribe(new ProducingSubscriber(asyncContext, context));
+			DeferredResult<?> deferredResult = new DeferredResult<>();
+			AsyncServerResponse.writeAsync(servletRequest, servletResponse, deferredResult);
+
+			entity().subscribe(new DeferredResultSubscriber(servletRequest, servletResponse, context, deferredResult));
 			return null;
 		}
 
-		@SuppressWarnings("SubscriberImplementation")
-		private class ProducingSubscriber implements Subscriber<T> {
 
-			private final AsyncContext asyncContext;
+		private class DeferredResultSubscriber implements Subscriber<T> {
+
+			private final HttpServletRequest servletRequest;
+
+			private final HttpServletResponse servletResponse;
 
 			private final Context context;
 
+			private final DeferredResult<?> deferredResult;
+
 			@Nullable
 			private Subscription subscription;
 
-			public ProducingSubscriber(AsyncContext asyncContext, Context context) {
-				this.asyncContext = asyncContext;
+
+			public DeferredResultSubscriber(HttpServletRequest servletRequest,
+					HttpServletResponse servletResponse, Context context,
+					DeferredResult<?> deferredResult) {
+
+				this.servletRequest = servletRequest;
+				this.servletResponse = new NoContentLengthResponseWrapper(servletResponse);
 				this.context = context;
+				this.deferredResult = deferredResult;
 			}
 
 			@Override
 			public void onSubscribe(Subscription s) {
 				if (this.subscription == null) {
 					this.subscription = s;
-					this.subscription.request(Long.MAX_VALUE);
+					this.subscription.request(1);
 				}
 				else {
 					s.cancel();
@@ -435,32 +454,34 @@ final class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T>
 			}
 
 			@Override
-			public void onNext(T element) {
-				HttpServletRequest servletRequest = (HttpServletRequest) this.asyncContext.getRequest();
-				HttpServletResponse servletResponse = (HttpServletResponse) this.asyncContext.getResponse();
+			public void onNext(T t) {
+				Assert.state(this.subscription != null, "No subscription");
 				try {
-					tryWriteEntityWithMessageConverters(element, servletRequest, servletResponse, this.context);
+					tryWriteEntityWithMessageConverters(t, this.servletRequest, this.servletResponse, this.context);
+					this.servletResponse.getOutputStream().flush();
+					this.subscription.request(1);
 				}
 				catch (ServletException | IOException ex) {
-					onError(ex);
+					this.subscription.cancel();
+					this.deferredResult.setErrorResult(ex);
 				}
 			}
 
 			@Override
 			public void onError(Throwable t) {
-				try {
-					handleError(t, (HttpServletRequest) this.asyncContext.getRequest(),
-							(HttpServletResponse) this.asyncContext.getResponse(), this.context);
-				}
-				catch (ServletException | IOException ex) {
-					logger.warn("Asynchronous execution resulted in exception", ex);
-				}
-				this.asyncContext.complete();
+				this.deferredResult.setErrorResult(t);
 			}
 
 			@Override
 			public void onComplete() {
-				this.asyncContext.complete();
+				try {
+					this.servletResponse.getOutputStream().flush();
+					this.deferredResult.setResult(null);
+				}
+				catch (IOException ex) {
+					this.deferredResult.setErrorResult(ex);
+				}
+
 			}
 		}
 

spring-webmvc/src/main/java/org/springframework/web/servlet/function/ServerResponse.java

@@ -18,6 +18,7 @@ package org.springframework.web.servlet.function;
 
 import java.io.IOException;
 import java.net.URI;
+import java.time.Duration;
 import java.time.Instant;
 import java.time.ZonedDateTime;
 import java.util.Collection;
@@ -240,7 +241,33 @@ public interface ServerResponse {
 	 * @since 5.3
 	 */
 	static ServerResponse async(Object asyncResponse) {
-		return AsyncServerResponse.create(asyncResponse);
+		return AsyncServerResponse.create(asyncResponse, null);
+	}
+
+	/**
+	 * Create a (built) response with the given asynchronous response.
+	 * Parameter {@code asyncResponse} can be a
+	 * {@link CompletableFuture CompletableFuture<ServerResponse>} or
+	 * {@link Publisher Publisher<ServerResponse>} (or any
+	 * asynchronous producer of a single {@code ServerResponse} that can be
+	 * adapted via the {@link ReactiveAdapterRegistry}).
+	 *
+	 * <p>This method can be used to set the response status code, headers, and
+	 * body based on an asynchronous result. If only the body is asynchronous,
+	 * {@link BodyBuilder#body(Object)} can be used instead.
+	 *
+	 * <p><strong>Note</strong> that
+	 * {@linkplain RenderingResponse rendering responses}, as returned by
+	 * {@link BodyBuilder#render}, are <strong>not</strong> supported as value
+	 * for {@code asyncResponse}. Use WebFlux.fn for asynchronous rendering.
+	 * @param asyncResponse a {@code CompletableFuture<ServerResponse>} or
+	 * {@code Publisher<ServerResponse>}
+	 * @param timeout maximum time period to wait for before timing out
+	 * @return the asynchronous response
+	 * @since 5.3.2
+	 */
+	static ServerResponse async(Object asyncResponse, Duration timeout) {
+		return AsyncServerResponse.create(asyncResponse, timeout);
 	}
 
 

spring-webmvc/src/main/java/org/springframework/web/servlet/function/support/HandlerFunctionAdapter.java

@@ -18,13 +18,21 @@ package org.springframework.web.servlet.function.support;
 
 import java.util.List;
 
+import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
 import org.springframework.core.Ordered;
+import org.springframework.core.log.LogFormatUtils;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.web.context.request.async.AsyncWebRequest;
+import org.springframework.web.context.request.async.WebAsyncManager;
+import org.springframework.web.context.request.async.WebAsyncUtils;
 import org.springframework.web.servlet.HandlerAdapter;
 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.function.HandlerFunction;
@@ -40,8 +48,12 @@ import org.springframework.web.servlet.function.ServerResponse;
  */
 public class HandlerFunctionAdapter implements HandlerAdapter, Ordered {
 
+	private static final Log logger = LogFactory.getLog(HandlerFunctionAdapter.class);
+
 	private int order = Ordered.LOWEST_PRECEDENCE;
 
+	@Nullable
+	private Long asyncRequestTimeout;
 
 	/**
 	 * Specify the order value for this HandlerAdapter bean.
@@ -57,6 +69,19 @@ public class HandlerFunctionAdapter implements HandlerAdapter, Ordered {
 		return this.order;
 	}
 
+	/**
+	 * Specify the amount of time, in milliseconds, before concurrent handling
+	 * should time out. In Servlet 3, the timeout begins after the main request
+	 * processing thread has exited and ends when the request is dispatched again
+	 * for further processing of the concurrently produced result.
+	 * <p>If this value is not set, the default timeout of the underlying
+	 * implementation is used.
+	 * @param timeout the timeout value in milliseconds
+	 */
+	public void setAsyncRequestTimeout(long timeout) {
+		this.asyncRequestTimeout = timeout;
+	}
+
 	@Override
 	public boolean supports(Object handler) {
 		return handler instanceof HandlerFunction;
@@ -68,14 +93,34 @@ public class HandlerFunctionAdapter implements HandlerAdapter, Ordered {
 			HttpServletResponse servletResponse,
 			Object handler) throws Exception {
 
-
-		HandlerFunction<?> handlerFunction = (HandlerFunction<?>) handler;
+		WebAsyncManager asyncManager = getWebAsyncManager(servletRequest, servletResponse);
 
 		ServerRequest serverRequest = getServerRequest(servletRequest);
-		ServerResponse serverResponse = handlerFunction.handle(serverRequest);
+		ServerResponse serverResponse;
 
-		return serverResponse.writeTo(servletRequest, servletResponse,
-				new ServerRequestContext(serverRequest));
+		if (asyncManager.hasConcurrentResult()) {
+			serverResponse = handleAsync(asyncManager);
+		}
+		else {
+			HandlerFunction<?> handlerFunction = (HandlerFunction<?>) handler;
+			serverResponse = handlerFunction.handle(serverRequest);
+		}
+
+		if (serverResponse != null) {
+			return serverResponse.writeTo(servletRequest, servletResponse, new ServerRequestContext(serverRequest));
+		}
+		else {
+			return null;
+		}
+	}
+
+	private WebAsyncManager getWebAsyncManager(HttpServletRequest servletRequest, HttpServletResponse servletResponse) {
+		AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(servletRequest, servletResponse);
+		asyncWebRequest.setTimeout(this.asyncRequestTimeout);
+
+		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(servletRequest);
+		asyncManager.setAsyncWebRequest(asyncWebRequest);
+		return asyncManager;
 	}
 
 	private ServerRequest getServerRequest(HttpServletRequest servletRequest) {
@@ -86,6 +131,31 @@ public class HandlerFunctionAdapter implements HandlerAdapter, Ordered {
 		return serverRequest;
 	}
 
+	@Nullable
+	private ServerResponse handleAsync(WebAsyncManager asyncManager) throws Exception {
+		Object result = asyncManager.getConcurrentResult();
+		asyncManager.clearConcurrentResult();
+		LogFormatUtils.traceDebug(logger, traceOn -> {
+			String formatted = LogFormatUtils.formatValue(result, !traceOn);
+			return "Resume with async result [" + formatted + "]";
+		});
+		if (result instanceof ServerResponse) {
+			return (ServerResponse) result;
+		}
+		else if (result instanceof Exception) {
+			throw (Exception) result;
+		}
+		else if (result instanceof Throwable) {
+			throw new ServletException("Async processing failed", (Throwable) result);
+		}
+		else if (result == null) {
+			return null;
+		}
+		else {
+			throw new IllegalArgumentException("Unknown result from WebAsyncManager: [" + result + "]");
+		}
+	}
+
 	@Override
 	public long getLastModified(HttpServletRequest request, Object handler) {
 		return -1L;

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerAdapter.java

@@ -880,7 +880,10 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 			asyncManager.registerCallableInterceptors(this.callableInterceptors);
 			asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);
 
-			if (asyncManager.hasConcurrentResult()) {
+			if (asyncManager.hasConcurrentResult() &&
+					asyncManager.getConcurrentResultContext().length > 0 &&
+					asyncManager.getConcurrentResultContext()[0] instanceof ModelAndViewContainer) {
+
 				Object result = asyncManager.getConcurrentResult();
 				mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
 				asyncManager.clearConcurrentResult();