Polish

Replacing a couple of calls to Mono.fromCallable with Mono.just which
seems to work with doOnDiscard except when nested inside Flux.defer.

spring-web/src/main/java/org/springframework/http/codec/EncoderHttpMessageWriter.java

@@ -125,16 +125,14 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 					}))
 					.flatMap(buffer -> {
 						headers.setContentLength(buffer.readableByteCount());
-						return message.writeWith(
-								Mono.fromCallable(() -> buffer)
-										.doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release));
+						return message.writeWith(Mono.just(buffer)
+								.doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release));
 					});
 		}
 
 		if (isStreamingMediaType(contentType)) {
 			return message.writeAndFlushWith(body.map(buffer ->
-					Mono.fromCallable(() -> buffer)
-							.doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release)));
+					Mono.just(buffer).doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release)));
 		}
 
 		return message.writeWith(body);

spring-web/src/main/java/org/springframework/http/codec/xml/Jaxb2XmlEncoder.java

@@ -108,7 +108,7 @@ public class Jaxb2XmlEncoder extends AbstractSingleValueEncoder<Object> {
 			});
 		}
 
-		return Flux.defer(() -> {
+		return Mono.fromCallable(() -> {
 			boolean release = true;
 			DataBuffer buffer = bufferFactory.allocateBuffer(1024);
 			try {
@@ -117,21 +117,21 @@ public class Jaxb2XmlEncoder extends AbstractSingleValueEncoder<Object> {
 				Marshaller marshaller = initMarshaller(clazz);
 				marshaller.marshal(value, outputStream);
 				release = false;
-				return Mono.fromCallable(() -> buffer);  // relying on doOnDiscard in base class
+				return buffer;  // relying on doOnDiscard in base class
 			}
 			catch (MarshalException ex) {
-				return Flux.error(new EncodingException(
-						"Could not marshal " + value.getClass() + " to XML", ex));
+				throw new EncodingException(
+						"Could not marshal " + value.getClass() + " to XML", ex);
 			}
 			catch (JAXBException ex) {
-				return Flux.error(new CodecException("Invalid JAXB configuration", ex));
+				throw new CodecException("Invalid JAXB configuration", ex);
 			}
 			finally {
 				if (release) {
 					DataBufferUtils.release(buffer);
 				}
 			}
-		});
+		}).flux();
 	}
 
 	private Marshaller initMarshaller(Class<?> clazz) throws JAXBException {

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/ModelAttributeMethodArgumentResolver.java

@@ -135,8 +135,7 @@ public class ModelAttributeMethodArgumentResolver extends HandlerMethodArgumentR
 						BindingResult errors = binder.getBindingResult();
 						if (adapter != null) {
 							return adapter.fromPublisher(errors.hasErrors() ?
-									Mono.error(new WebExchangeBindException(parameter, errors)) :
-									valueMono);
+									Mono.error(new WebExchangeBindException(parameter, errors)) : valueMono);
 						}
 						else {
 							if (errors.hasErrors() && !hasErrorsArgument(parameter)) {