Support for @RequestPart with reactive type wrapper

Issue: SPR-14546

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

@@ -48,9 +48,6 @@ import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.WebSession;
 import org.springframework.web.server.session.WebSessionManager;
 
-import static org.springframework.http.MediaType.APPLICATION_FORM_URLENCODED;
-import static org.springframework.http.MediaType.MULTIPART_FORM_DATA;
-
 /**
  * Default implementation of {@link ServerWebExchange}.
  *
@@ -61,10 +58,10 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 
 	private static final List<HttpMethod> SAFE_METHODS = Arrays.asList(HttpMethod.GET, HttpMethod.HEAD);
 
-	private static final ResolvableType FORM_DATA_VALUE_TYPE =
+	private static final ResolvableType FORM_DATA_TYPE =
 			ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class);
 
-	private static final ResolvableType MULTIPART_VALUE_TYPE = ResolvableType.forClassWithGenerics(
+	private static final ResolvableType MULTIPART_DATA_TYPE = ResolvableType.forClassWithGenerics(
 			MultiValueMap.class, String.class, Part.class);
 
 	private static final Mono<MultiValueMap<String, String>> EMPTY_FORM_DATA =
@@ -110,21 +107,17 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 	}
 
 	@SuppressWarnings("unchecked")
-	private static Mono<MultiValueMap<String, String>> initFormData(
-			ServerHttpRequest request, ServerCodecConfigurer codecConfigurer) {
+	private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request,
+			ServerCodecConfigurer configurer) {
 
-		MediaType contentType;
 		try {
-			contentType = request.getHeaders().getContentType();
-			if (APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
-				return ((HttpMessageReader<MultiValueMap<String, String>>)codecConfigurer
-						.getReaders()
-						.stream()
-						.filter(reader -> reader.canRead(FORM_DATA_VALUE_TYPE, APPLICATION_FORM_URLENCODED))
+			MediaType contentType = request.getHeaders().getContentType();
+			if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
+				return ((HttpMessageReader<MultiValueMap<String, String>>) configurer.getReaders().stream()
+						.filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
 						.findFirst()
-						.orElseThrow(() -> new IllegalStateException(
-								"Could not find HttpMessageReader that supports " + APPLICATION_FORM_URLENCODED)))
-						.readMono(FORM_DATA_VALUE_TYPE, request, Collections.emptyMap())
+						.orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
+						.readMono(FORM_DATA_TYPE, request, Collections.emptyMap())
 						.switchIfEmpty(EMPTY_FORM_DATA)
 						.cache();
 			}
@@ -136,21 +129,17 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 	}
 
 	@SuppressWarnings("unchecked")
-	private static Mono<MultiValueMap<String, Part>> initMultipartData(
-			ServerHttpRequest request, ServerCodecConfigurer codecConfigurer) {
+	private static Mono<MultiValueMap<String, Part>> initMultipartData(ServerHttpRequest request,
+			ServerCodecConfigurer configurer) {
 
-		MediaType contentType;
 		try {
-			contentType = request.getHeaders().getContentType();
-			if (MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
-				return ((HttpMessageReader<MultiValueMap<String, Part>>) codecConfigurer
-						.getReaders()
-						.stream()
-						.filter(reader -> reader.canRead(MULTIPART_VALUE_TYPE, MULTIPART_FORM_DATA))
+			MediaType contentType = request.getHeaders().getContentType();
+			if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
+				return ((HttpMessageReader<MultiValueMap<String, Part>>) configurer.getReaders().stream()
+						.filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
 						.findFirst()
-						.orElseThrow(() -> new IllegalStateException(
-								"Could not find HttpMessageReader that supports " + MULTIPART_FORM_DATA)))
-						.readMono(FORM_DATA_VALUE_TYPE, request, Collections.emptyMap())
+						.orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
+						.readMono(MULTIPART_DATA_TYPE, request, Collections.emptyMap())
 						.switchIfEmpty(EMPTY_MULTIPART_DATA)
 						.cache();
 			}

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

@@ -21,6 +21,7 @@ import java.util.List;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.util.CollectionUtils;
@@ -61,13 +62,16 @@ public class RequestPartMethodArgumentResolver extends AbstractNamedValueArgumen
 
 	@Override
 	protected Mono<Object> resolveName(String name, MethodParameter param, ServerWebExchange exchange) {
-		return exchange.getMultipartData().flatMap(allParts -> {
-			List<Part> parts = allParts.get(name);
-			if (CollectionUtils.isEmpty(parts)) {
-				return Mono.empty();
-			}
-			return Mono.just(parts.size() == 1 ? parts.get(0) : parts);
+
+		Mono<Object> partsMono = exchange.getMultipartData()
+				.filter(map -> !CollectionUtils.isEmpty(map.get(name)))
+				.map(map -> {
+					List<Part> parts = map.get(name);
+					return parts.size() == 1 ? parts.get(0) : parts;
 				});
+
+		ReactiveAdapter adapter = getAdapterRegistry().getAdapter(param.getParameterType());
+		return (adapter != null ? Mono.just(adapter.fromPublisher(partsMono)) : partsMono);
 	}
 
 	@Override

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MultipartIntegrationTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.reactive.result.method.annotation;
 
+import java.time.Duration;
 import java.util.Map;
 import java.util.stream.Collectors;
 
@@ -34,6 +35,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.multipart.FilePart;
+import org.springframework.http.codec.multipart.FormFieldPart;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.reactive.AbstractHttpHandlerIntegrationTests;
 import org.springframework.http.server.reactive.HttpHandler;
@@ -152,8 +154,9 @@ public class MultipartIntegrationTests extends AbstractHttpHandlerIntegrationTes
 	static class MultipartController {
 
 		@PostMapping("/requestPart")
-		void requestPart(@RequestPart Part fooPart) {
-			assertEquals("foo.txt", ((FilePart) fooPart).getFilename());
+		void requestPart(@RequestPart FormFieldPart barPart, @RequestPart Mono<FilePart> fooPart) {
+			assertEquals("bar", barPart.getValue());
+			assertEquals("foo.txt", fooPart.block(Duration.ZERO).getFilename());
 		}
 
 		@PostMapping("/requestBodyMap")