Log and handle unresolved exceptions

Before this change use of ExceptionHandlingWebHandler did ensure no
error signals are allowed to escape (hence relying on runtime
behavior).

This change ensures the same is done even when
ExceptionHandlingWebHandler is not configured for use, at the lowest
level which is the WebToHttpHandlerAdapter.

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

@@ -62,8 +62,8 @@ public class SimpleHandlerResultHandler implements Ordered, HandlerResultHandler
 	@Override
 	public boolean supports(HandlerResult result) {
 		ResolvableType type = result.getResultType();
-		return type != null && Void.TYPE.equals(type.getRawClass()) ||
-				(Void.class.isAssignableFrom(type.getGeneric(0).getRawClass()) && isConvertibleToPublisher(type));
+		return (type != null && Void.TYPE.equals(type.getRawClass()) ||
+				(isConvertibleToPublisher(type) && Void.class.isAssignableFrom(type.getGeneric(0).getRawClass())));
 	}
 
 	private boolean isConvertibleToPublisher(ResolvableType type) {

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

@@ -19,6 +19,8 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import reactor.Mono;
 
 import org.springframework.http.HttpStatus;
@@ -31,6 +33,9 @@ import org.springframework.http.HttpStatus;
  */
 public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
 
+	private static Log logger = LogFactory.getLog(ExceptionHandlingWebHandler.class);
+
+
 	private final List<WebExceptionHandler> exceptionHandlers;
 
 
@@ -51,6 +56,7 @@ public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
 		return this.exceptionHandlers;
 	}
 
+
 	@Override
 	public Mono<Void> handle(WebServerExchange exchange) {
 		Mono<Void> mono;
@@ -63,10 +69,13 @@ public class ExceptionHandlingWebHandler extends WebHandlerDecorator {
 		for (WebExceptionHandler exceptionHandler : this.exceptionHandlers) {
 			mono = mono.otherwise(ex -> exceptionHandler.handle(exchange, ex));
 		}
-		return mono.otherwise(ex -> handleUnresolvedException(exchange));
+		return mono.otherwise(ex -> handleUnresolvedException(exchange, ex));
 	}
 
-	private Mono<? extends Void> handleUnresolvedException(WebServerExchange exchange) {
+	private Mono<? extends Void> handleUnresolvedException(WebServerExchange exchange, Throwable ex) {
+		if (logger.isDebugEnabled()) {
+			logger.debug("Could not complete request", ex);
+		}
 		exchange.getResponse().setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
 		return Mono.empty();
 	}

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

@@ -15,8 +15,11 @@
  */
 package org.springframework.web.server;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import reactor.Mono;
 
+import org.springframework.http.HttpStatus;
 import org.springframework.http.server.reactive.HttpHandler;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
@@ -29,15 +32,28 @@ import org.springframework.http.server.reactive.ServerHttpResponse;
  */
 public class WebToHttpHandlerAdapter extends WebHandlerDecorator implements HttpHandler {
 
+	private static Log logger = LogFactory.getLog(WebToHttpHandlerAdapter.class);
+
 
 	public WebToHttpHandlerAdapter(WebHandler delegate) {
 		super(delegate);
 	}
 
+
 	@Override
 	public Mono<Void> handle(ServerHttpRequest request, ServerHttpResponse response) {
 		WebServerExchange exchange = createWebServerExchange(request, response);
-		return getDelegate().handle(exchange).doOnTerminate((aVoid, ex) -> response.writeHeaders());
+		return getDelegate().handle(exchange).otherwise(ex -> {
+					if (logger.isDebugEnabled()) {
+						logger.debug("Could not complete request", ex);
+					}
+					response.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR);
+					return Mono.empty();
+				})
+				.doOnTerminate((aVoid, ex) -> {
+					response.writeHeaders();
+				});
+
 	}
 
 	protected WebServerExchange createWebServerExchange(ServerHttpRequest request, ServerHttpResponse response) {