Handle errors via AsyncListener

This is a limited backport of commit #e0678b mainly providing the fix without
exposing the onError callbacks.

Issue: SPR-16058

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/context/request/async/StandardServletAsyncWebRequest.java

@@ -50,6 +50,8 @@ public class StandardServletAsyncWebRequest extends ServletWebRequest implements
 
 	private final List<Runnable> timeoutHandlers = new ArrayList<Runnable>();
 
+	private ErrorHandler errorHandler;
+
 	private final List<Runnable> completionHandlers = new ArrayList<Runnable>();
 
 
@@ -78,6 +80,10 @@ public void addTimeoutHandler(Runnable timeoutHandler) {
 		this.timeoutHandlers.add(timeoutHandler);
 	}
 
+	void setErrorHandler(ErrorHandler errorHandler) {
+		this.errorHandler = errorHandler;
+	}
+
 	@Override
 	public void addCompletionHandler(Runnable runnable) {
 		this.completionHandlers.add(runnable);
@@ -134,7 +140,9 @@ public void onStartAsync(AsyncEvent event) throws IOException {
 
 	@Override
 	public void onError(AsyncEvent event) throws IOException {
-		onComplete(event);
+		if (this.errorHandler != null) {
+			this.errorHandler.handle(event.getThrowable());
+		}
 	}
 
 	@Override
@@ -153,4 +161,11 @@ public void onComplete(AsyncEvent event) throws IOException {
 		this.asyncCompleted.set(true);
 	}
 
+
+	interface ErrorHandler {
+
+		void handle(Throwable ex);
+
+	}
+
 }

spring-web/src/main/java/org/springframework/web/context/request/async/WebAsyncManager.java

@@ -298,6 +298,16 @@ public void run() {
 			}
 		});
 
+		if (this.asyncWebRequest instanceof StandardServletAsyncWebRequest) {
+			((StandardServletAsyncWebRequest) this.asyncWebRequest).setErrorHandler(
+					new StandardServletAsyncWebRequest.ErrorHandler() {
+						@Override
+						public void handle(Throwable ex) {
+							setConcurrentResultAndDispatch(ex);
+						}
+					});
+		}
+
 		this.asyncWebRequest.addCompletionHandler(new Runnable() {
 			@Override
 			public void run() {
@@ -399,6 +409,16 @@ public void run() {
 			}
 		});
 
+		if (this.asyncWebRequest instanceof StandardServletAsyncWebRequest) {
+			((StandardServletAsyncWebRequest) this.asyncWebRequest).setErrorHandler(
+					new StandardServletAsyncWebRequest.ErrorHandler() {
+						@Override
+						public void handle(Throwable ex) {
+							deferredResult.setErrorResult(ex);
+						}
+					});
+		}
+
 		this.asyncWebRequest.addCompletionHandler(new Runnable() {
 			@Override
 			public void run() {

spring-web/src/test/java/org/springframework/web/context/request/async/StandardServletAsyncWebRequestTests.java

@@ -25,6 +25,7 @@
 import org.springframework.mock.web.test.MockAsyncContext;
 import org.springframework.mock.web.test.MockHttpServletRequest;
 import org.springframework.mock.web.test.MockHttpServletResponse;
+import org.springframework.web.context.request.async.StandardServletAsyncWebRequest.ErrorHandler;
 
 import static org.hamcrest.Matchers.containsString;
 import static org.junit.Assert.assertEquals;
@@ -148,13 +149,26 @@ public void onCompletionHandler() throws Exception {
 
 	// SPR-13292
 
+	@SuppressWarnings("unchecked")
 	@Test
-	public void onCompletionHandlerAfterOnErrorEvent() throws Exception {
+	public void onErrorHandlerAfterOnErrorEvent() throws Exception {
+		ErrorHandler handler = mock(ErrorHandler.class);
+		this.asyncRequest.setErrorHandler(handler);
+
+		this.asyncRequest.startAsync();
+		Exception e = new Exception();
+		this.asyncRequest.onError(new AsyncEvent(this.request.getAsyncContext(), e));
+
+		verify(handler).handle(e);
+	}
+
+	@Test
+	public void onCompletionHandlerAfterOnCompleteEvent() throws Exception {
 		Runnable handler = mock(Runnable.class);
 		this.asyncRequest.addCompletionHandler(handler);
 
 		this.asyncRequest.startAsync();
-		this.asyncRequest.onError(new AsyncEvent(null));
+		this.asyncRequest.onComplete(new AsyncEvent(this.request.getAsyncContext()));
 
 		verify(handler).run();
 		assertTrue(this.asyncRequest.isAsyncComplete());

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

@@ -166,11 +166,9 @@ private void sendInternal(Object object, MediaType mediaType) throws IOException
 					this.handler.send(object, mediaType);
 				}
 				catch (IOException ex) {
-					completeWithError(ex);
 					throw ex;
 				}
 				catch (Throwable ex) {
-					completeWithError(ex);
 					throw new IllegalStateException("Failed to send " + object, ex);
 				}
 			}

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitterTests.java

@@ -150,7 +150,6 @@ public void sendWithError() throws Exception {
 			// expected
 		}
 		verify(this.handler).send("foo", MediaType.TEXT_PLAIN);
-		verify(this.handler).completeWithError(failure);
 		verifyNoMoreInteractions(this.handler);
 	}