Polish (major) MVC async processing interceptors

New afterTimeout and afterCompletion callbacks

afterTimeout can provide a concurrent result to be used instead of the
one that could not be set or returned on time

Interceptor exceptions cause async processing to resume treating the
exception as the concurrent result

Adapter classes for convenient implementation of the interfaces

Issue: SPR-9914

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

@@ -50,6 +50,7 @@ import org.springframework.web.context.request.RequestAttributes;
 import org.springframework.web.context.request.RequestContextHolder;
 import org.springframework.web.context.request.ServletRequestAttributes;
 import org.springframework.web.context.request.async.CallableProcessingInterceptor;
+import org.springframework.web.context.request.async.CallableProcessingInterceptorAdapter;
 import org.springframework.web.context.request.async.WebAsyncManager;
 import org.springframework.web.context.request.async.WebAsyncUtils;
 import org.springframework.web.context.support.ServletRequestHandledEvent;
@@ -988,14 +989,13 @@ public abstract class FrameworkServlet extends HttpServletBean {
 	}
 
 	private CallableProcessingInterceptor createRequestBindingInterceptor(final HttpServletRequest request) {
-
-		return new CallableProcessingInterceptor() {
-
-			public void preProcess(NativeWebRequest webRequest, Callable<?> task) {
+		return new CallableProcessingInterceptorAdapter() {
+			@Override
+			public <T> void preProcess(NativeWebRequest webRequest, Callable<T> task) {
 				initContextHolders(request, buildLocaleContext(request), new ServletRequestAttributes(request));
 			}
-
-			public void postProcess(NativeWebRequest webRequest, Callable<?> task, Object concurrentResult) {
+			@Override
+			public <T> void postProcess(NativeWebRequest webRequest, Callable<T> task, Object concurrentResult) {
 				resetContextHolders(request, null, null);
 			}
 		};