Polish @RequestPart support

spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java

@@ -312,6 +312,9 @@ public abstract class MimeTypeUtils {
 		}
 	}
 
+
+
+
 	/**
 	 * Generate a random MIME boundary as bytes, often used in multipart mime types.
 	 */

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,6 @@
 
 package org.springframework.web.reactive.result.method.annotation;
 
-import java.util.Collections;
 import java.util.List;
 
 import reactor.core.publisher.Flux;
@@ -75,25 +74,31 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageReaderArgu
 		boolean isRequired = (requestPart == null || requestPart.required());
 		String name = getPartName(parameter, requestPart);
 
-		Flux<Part> partFlux = getPartValues(name, exchange);
+		Flux<Part> values = exchange.getMultipartData()
-		if (isRequired) {
+				.flatMapMany(map -> {
-			partFlux = partFlux.switchIfEmpty(Flux.error(getMissingPartException(name, parameter)));
+					List<Part> parts = map.get(name);
-		}
+					if (CollectionUtils.isEmpty(parts)) {
+						return isRequired ?
+								Flux.error(getMissingPartException(name, parameter)) :
+								Flux.empty();
+					}
+					return Flux.fromIterable(parts);
+				});
 
 		ReactiveAdapter adapter = getAdapterRegistry().getAdapter(parameter.getParameterType());
 		MethodParameter elementType = adapter != null ? parameter.nested() : parameter;
 
 		if (Part.class.isAssignableFrom(elementType.getNestedParameterType())) {
 			if (adapter != null) {
-				partFlux = adapter.isMultiValue() ? partFlux : partFlux.take(1);
+				values = adapter.isMultiValue() ? values : values.take(1);
-				return Mono.just(adapter.fromPublisher(partFlux));
+				return Mono.just(adapter.fromPublisher(values));
 			}
 			else {
-				return partFlux.next().cast(Object.class);
+				return values.next().cast(Object.class);
 			}
 		}
 
-		return partFlux.next().flatMap(part -> {
+		return values.next().flatMap(part -> {
 			ServerHttpRequest partRequest = new PartServerHttpRequest(exchange.getRequest(), part);
 			ServerWebExchange partExchange = exchange.mutate().request(partRequest).build();
 			return readBody(parameter, isRequired, bindingContext, partExchange);
@@ -113,12 +118,6 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageReaderArgu
 		return partName;
 	}
 
-	private Flux<Part> getPartValues(String name, ServerWebExchange exchange) {
-		return exchange.getMultipartData()
-				.filter(map -> !CollectionUtils.isEmpty(map.get(name)))
-				.flatMapIterable(map -> map.getOrDefault(name, Collections.emptyList()));
-	}
-
 	private ServerWebInputException getMissingPartException(String name, MethodParameter param) {
 		String reason = "Required request part '" + name + "' is not present";
 		return new ServerWebInputException(reason, param);

src/docs/asciidoc/web/webflux.adoc

@@ -1789,27 +1789,26 @@ Content-Transfer-Encoding: 8bit
 ... File Data ...
 ----
 
-You can access the "meta-data" part with `@RequestPart` which would deserialize it from
+You can access individual parts with `@RequestPart`:
-JSON (similar to `@RequestBody`) through one of the configured <<webflux-codecs>>:
 
 [source,java,indent=0]
 [subs="verbatim,quotes"]
 ----
 	@PostMapping("/")
-	public String handle(**@RequestPart("meta-data") MetaData metadata,
+	public String handle(**@RequestPart("meta-data") Part metadata,
 			@RequestPart("file-data") FilePart file**) {
 		// ...
 	}
 ----
 
-To access multipart data sequentially, in streaming fashion, use `@RequestBody` with
+To deserialize the raw part content, for example to JSON (similar to `@RequestBody`),
-`Flux<Part>` instead. For example:
+simply declare a concrete target Object, instead of `Part`:
 
 [source,java,indent=0]
 [subs="verbatim,quotes"]
 ----
 	@PostMapping("/")
-	public String handle(**@RequestBody Flux<Part> parts**) {
+	public String handle(**@RequestPart("meta-data") MetaData metadata**) {
 		// ...
 	}
 ----
@@ -1830,6 +1829,29 @@ public String handle(**@Valid** @RequestPart("meta-data") MetaData metadata,
 }
 ----
 
+To access all multipart data in as a `MultiValueMap` use `@RequestBody`:
+
+[source,java,indent=0]
+[subs="verbatim,quotes"]
+----
+	@PostMapping("/")
+	public String handle(**@RequestBody Mono<MultiValueMap<String, Part>> parts**) {
+		// ...
+	}
+----
+
+To access multipart data sequentially, in streaming fashion, use `@RequestBody` with
+`Flux<Part>` instead. For example:
+
+[source,java,indent=0]
+[subs="verbatim,quotes"]
+----
+	@PostMapping("/")
+	public String handle(**@RequestBody Flux<Part> parts**) {
+		// ...
+	}
+----
+
 
 [[webflux-ann-requestbody]]
 ==== @RequestBody