Log unresolved exceptions at error level

spring-web/src/main/java/org/springframework/http/server/reactive/ReactorHttpHandlerAdapter.java

@@ -54,7 +54,7 @@ public class ReactorHttpHandlerAdapter implements Function<HttpChannel, Mono<Voi
 
 		return this.delegate.handle(adaptedRequest, adaptedResponse)
 				.otherwise(ex -> {
-					logger.debug("Could not complete request", ex);
+					logger.error("Could not complete request", ex);
 					channel.status(HttpResponseStatus.INTERNAL_SERVER_ERROR);
 					return Mono.empty();
 				})

spring-web/src/main/java/org/springframework/http/server/reactive/RxNettyHttpHandlerAdapter.java

@@ -58,7 +58,7 @@ public class RxNettyHttpHandlerAdapter implements RequestHandler<ByteBuf, ByteBu
 
 		Publisher<Void> result = this.delegate.handle(adaptedRequest, adaptedResponse)
 				.otherwise(ex -> {
-					logger.debug("Could not complete request", ex);
+					logger.error("Could not complete request", ex);
 					response.setStatus(HttpResponseStatus.INTERNAL_SERVER_ERROR);
 					return Mono.empty();
 				})

spring-web/src/main/java/org/springframework/http/server/reactive/ServletHttpHandlerAdapter.java

@@ -114,7 +114,7 @@ public class ServletHttpHandlerAdapter extends HttpServlet {
 
 		@Override
 		public void onError(Throwable ex) {
-			logger.debug("Could not complete request", ex);
+			logger.error("Could not complete request", ex);
 			HttpServletResponse response = (HttpServletResponse) this.asyncContext.getResponse();
 			response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
 			this.asyncContext.complete();

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowHttpHandlerAdapter.java

@@ -72,7 +72,7 @@ public class UndertowHttpHandlerAdapter implements io.undertow.server.HttpHandle
 			}
 			@Override
 			public void onError(Throwable ex) {
-				logger.debug("Could not complete request", ex);
+				logger.error("Could not complete request", ex);
 				if (!exchange.isResponseStarted() && exchange.getStatusCode() <= 500) {
 					exchange.setStatusCode(500);
 				}

spring-web/src/main/java/org/springframework/web/server/adapter/WebHttpHandlerBuilder.java

@@ -123,10 +123,8 @@ public class WebHttpHandlerBuilder {
 			WebFilter[] array = new WebFilter[this.filters.size()];
 			webHandler = new FilteringWebHandler(webHandler, this.filters.toArray(array));
 		}
-		if (!this.exceptionHandlers.isEmpty()) {
-			WebExceptionHandler[] array = new WebExceptionHandler[this.exceptionHandlers.size()];
-			webHandler = new ExceptionHandlingWebHandler(webHandler,  this.exceptionHandlers.toArray(array));
-		}
+		WebExceptionHandler[] array = new WebExceptionHandler[this.exceptionHandlers.size()];
+		webHandler = new ExceptionHandlingWebHandler(webHandler,  this.exceptionHandlers.toArray(array));
 		HttpWebHandlerAdapter httpHandler = new HttpWebHandlerAdapter(webHandler);
 		if (this.sessionManager != null) {
 			httpHandler.setSessionManager(this.sessionManager);

spring-web/src/main/java/org/springframework/web/server/handler/ExceptionHandlingWebHandler.java

@@ -128,7 +128,7 @@ public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
 			}
 		}
 		else {
-			logger.debug("Could not complete request", ex);
+			logger.error("Could not complete request", ex);
 		}
 	}