Polishing contribution

Includes small refactoring in DefaultServerWebExchange and adjustment
of initMultipartData to get involved for any "multipart/" prefixed
media type.

In addition, "multipart/related" is now in the list of media types
supported by FormHttpMessageConverter, which aligns it with
MultipartHttpMessageReader.

Closes gh-29671

framework-docs/src/docs/asciidoc/web/webflux.adoc

@@ -614,7 +614,7 @@ The `DefaultServerWebExchange` uses the configured `HttpMessageReader` to parse
 
 The `DefaultServerWebExchange` uses the configured
 `HttpMessageReader<MultiValueMap<String, Part>>` to parse `multipart/form-data`,  
-`multipart/mixed` and `multipart/related` content into a `MultiValueMap`.
+`multipart/mixed`, and `multipart/related` content into a `MultiValueMap`.
 By default, this is the `DefaultPartHttpMessageReader`, which does not have any third-party
 dependencies.
 Alternatively, the `SynchronossPartHttpMessageReader` can be used, which is based on the
@@ -805,7 +805,7 @@ consistently for access to the cached form data versus reading from the raw requ
 ==== Multipart
 
 `MultipartHttpMessageReader` and `MultipartHttpMessageWriter` support decoding and
-encoding "multipart/form-data", "multipart/mixed" and "multipart/related" content. 
+encoding "multipart/form-data", "multipart/mixed", and "multipart/related" content.
 In turn `MultipartHttpMessageReader` delegates to another `HttpMessageReader` 
 for the actual parsing to a `Flux<Part>` and then simply collects the parts into a `MultiValueMap`.
 By default, the `DefaultPartHttpMessageReader` is used, but this can be changed through the

spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -176,6 +176,7 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 		this.supportedMediaTypes.add(MediaType.APPLICATION_FORM_URLENCODED);
 		this.supportedMediaTypes.add(MediaType.MULTIPART_FORM_DATA);
 		this.supportedMediaTypes.add(MediaType.MULTIPART_MIXED);
+		this.supportedMediaTypes.add(MediaType.MULTIPART_RELATED);
 
 		this.partConverters.add(new ByteArrayHttpMessageConverter());
 		this.partConverters.add(new StringHttpMessageConverter());

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -135,50 +135,68 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 		this.applicationContext = applicationContext;
 	}
 
-	@SuppressWarnings("unchecked")
 	private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request,
 			ServerCodecConfigurer configurer, String logPrefix) {
 
-		try {
-			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("No form data HttpMessageReader.")))
-						.readMono(FORM_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
-						.switchIfEmpty(EMPTY_FORM_DATA)
-						.cache();
-			}
+		MediaType contentType = getContentType(request);
+		if (contentType == null || !contentType.isCompatibleWith(MediaType.APPLICATION_FORM_URLENCODED)) {
+			return EMPTY_FORM_DATA;
 		}
-		catch (InvalidMediaTypeException ex) {
-			// Ignore
+
+		HttpMessageReader<MultiValueMap<String, String>> reader = getReader(configurer, contentType, FORM_DATA_TYPE);
+		if (reader == null) {
+			return Mono.error(new IllegalStateException("No HttpMessageReader for " + contentType));
 		}
-		return EMPTY_FORM_DATA;
+
+		return reader
+				.readMono(FORM_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
+				.switchIfEmpty(EMPTY_FORM_DATA)
+				.cache();
 	}
 
-	@SuppressWarnings("unchecked")
 	private static Mono<MultiValueMap<String, Part>> initMultipartData(ServerHttpRequest request,
 			ServerCodecConfigurer configurer, String logPrefix) {
 
+		MediaType contentType = getContentType(request);
+		if (contentType == null || !contentType.getType().equalsIgnoreCase("multipart")) {
+			return EMPTY_MULTIPART_DATA;
+		}
+
+		HttpMessageReader<MultiValueMap<String, Part>> reader = getReader(configurer, contentType, MULTIPART_DATA_TYPE);
+		if (reader == null) {
+			return Mono.error(new IllegalStateException("No HttpMessageReader for " + contentType));
+		}
+
+		return reader
+				.readMono(MULTIPART_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
+				.switchIfEmpty(EMPTY_MULTIPART_DATA)
+				.cache();
+	}
+
+	@Nullable
+	private static MediaType getContentType(ServerHttpRequest request) {
+		MediaType contentType = null;
 		try {
-			MediaType contentType = request.getHeaders().getContentType();
-			if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType) ||
-				MediaType.MULTIPART_MIXED.isCompatibleWith(contentType) ||
-				MediaType.MULTIPART_RELATED.isCompatibleWith(contentType)) {
-				return ((HttpMessageReader<MultiValueMap<String, Part>>) configurer.getReaders().stream()
-						.filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, contentType))
-						.findFirst()
-						.orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
-						.readMono(MULTIPART_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
-						.switchIfEmpty(EMPTY_MULTIPART_DATA)
-						.cache();
-			}
+			contentType = request.getHeaders().getContentType();
 		}
 		catch (InvalidMediaTypeException ex) {
-			// Ignore
+			// ignore
+		}
+		return contentType;
+	}
+
+	@SuppressWarnings("unchecked")
+	@Nullable
+	private static <E> HttpMessageReader<E> getReader(
+			ServerCodecConfigurer configurer, MediaType contentType, ResolvableType targetType) {
+
+		HttpMessageReader<E> result = null;
+		for (HttpMessageReader<?> reader : configurer.getReaders()) {
+			if (reader.canRead(targetType, contentType)) {
+				result = (HttpMessageReader<E>) reader;
+			}
 		}
-		return EMPTY_MULTIPART_DATA;
+		return result;
 	}
 
 

spring-web/src/test/java/org/springframework/http/converter/FormHttpMessageConverterTests.java

@@ -21,7 +21,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.StringReader;
 import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -53,6 +52,7 @@ import static org.springframework.http.MediaType.APPLICATION_FORM_URLENCODED;
 import static org.springframework.http.MediaType.APPLICATION_JSON;
 import static org.springframework.http.MediaType.MULTIPART_FORM_DATA;
 import static org.springframework.http.MediaType.MULTIPART_MIXED;
+import static org.springframework.http.MediaType.MULTIPART_RELATED;
 import static org.springframework.http.MediaType.TEXT_XML;
 
 /**
@@ -66,8 +66,6 @@ import static org.springframework.http.MediaType.TEXT_XML;
  */
 public class FormHttpMessageConverterTests {
 
-	private static final MediaType MULTIPART_RELATED = new MediaType("multipart", "related");
-
 	private final FormHttpMessageConverter converter = new AllEncompassingFormHttpMessageConverter();
 
 
@@ -85,8 +83,6 @@ public class FormHttpMessageConverterTests {
 		// Without custom multipart types supported
 		asssertCannotReadMultipart();
 
-		this.converter.addSupportedMediaTypes(MULTIPART_RELATED);
-
 		// Should still be the case with custom multipart types supported
 		asssertCannotReadMultipart();
 	}
@@ -96,6 +92,7 @@ public class FormHttpMessageConverterTests {
 		assertCanWrite(APPLICATION_FORM_URLENCODED);
 		assertCanWrite(MULTIPART_FORM_DATA);
 		assertCanWrite(MULTIPART_MIXED);
+		assertCanWrite(MULTIPART_RELATED);
 		assertCanWrite(new MediaType("multipart", "form-data", StandardCharsets.UTF_8));
 		assertCanWrite(MediaType.ALL);
 		assertCanWrite(null);
@@ -103,21 +100,19 @@ public class FormHttpMessageConverterTests {
 
 	@Test
 	public void setSupportedMediaTypes() {
-		assertCannotWrite(MULTIPART_RELATED);
+		this.converter.setSupportedMediaTypes(List.of(MULTIPART_FORM_DATA));
+		assertCannotWrite(MULTIPART_MIXED);
 
-		List<MediaType> supportedMediaTypes = new ArrayList<>(this.converter.getSupportedMediaTypes());
-		supportedMediaTypes.add(MULTIPART_RELATED);
-		this.converter.setSupportedMediaTypes(supportedMediaTypes);
-
-		assertCanWrite(MULTIPART_RELATED);
+		this.converter.setSupportedMediaTypes(List.of(MULTIPART_MIXED));
+		assertCanWrite(MULTIPART_MIXED);
 	}
 
 	@Test
 	public void addSupportedMediaTypes() {
-		assertCannotWrite(MULTIPART_RELATED);
+		this.converter.setSupportedMediaTypes(List.of(MULTIPART_FORM_DATA));
+		assertCannotWrite(MULTIPART_MIXED);
 
 		this.converter.addSupportedMediaTypes(MULTIPART_RELATED);
-
 		assertCanWrite(MULTIPART_RELATED);
 	}
 

spring-web/src/test/java/org/springframework/http/server/reactive/MultipartHttpHandlerIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 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.
@@ -32,7 +32,6 @@ import org.springframework.http.ResponseEntity;
 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.converter.FormHttpMessageConverter;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.client.RestTemplate;
@@ -56,44 +55,23 @@ class MultipartHttpHandlerIntegrationTests extends AbstractHttpHandlerIntegratio
 	}
 
 	@ParameterizedHttpServerTest
-	void getFormPartsFormdata(HttpServer httpServer) throws Exception {
-		performTest(httpServer, MediaType.MULTIPART_FORM_DATA);
+	void getMultipartFormData(HttpServer httpServer) throws Exception {
+		testMultipart(httpServer, MediaType.MULTIPART_FORM_DATA);
 	}
 
 	@ParameterizedHttpServerTest
-	void getFormPartsMixed(HttpServer httpServer) throws Exception {
-		performTest(httpServer, MediaType.MULTIPART_MIXED);
+	void getMultipartMixed(HttpServer httpServer) throws Exception {
+		testMultipart(httpServer, MediaType.MULTIPART_MIXED);
 	}
 
 	@ParameterizedHttpServerTest
-	void getFormPartsRelated(HttpServer httpServer) throws Exception {
-		RestTemplate restTemplate = new RestTemplate();
-		restTemplate.getMessageConverters().stream()
-				.filter(FormHttpMessageConverter.class::isInstance)
-				.map(FormHttpMessageConverter.class::cast)
-				.findFirst()
-				.orElseThrow()
-				.addSupportedMediaTypes(MediaType.MULTIPART_RELATED);
-		performTest(httpServer, MediaType.MULTIPART_RELATED, restTemplate);
+	void getMultipartRelated(HttpServer httpServer) throws Exception {
+		testMultipart(httpServer, MediaType.MULTIPART_RELATED);
 	}
 
-	private void performTest(HttpServer httpServer, MediaType mediaType) throws Exception {
-		performTest(httpServer, mediaType, new RestTemplate());
-	}
-
-	private void performTest(HttpServer httpServer, MediaType mediaType, RestTemplate restTemplate) throws Exception {
+	private void testMultipart(HttpServer httpServer, MediaType mediaType) throws Exception {
 		startServer(httpServer);
 
-		@SuppressWarnings("resource")
-		RequestEntity<MultiValueMap<String, Object>> request = RequestEntity
-				.post(URI.create("http://localhost:" + port + "/form-parts"))
-				.contentType(mediaType)
-				.body(generateBody());
-		ResponseEntity<Void> response = restTemplate.exchange(request, Void.class);
-		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
-	}
-
-	private MultiValueMap<String, Object> generateBody() {
 		HttpHeaders fooHeaders = new HttpHeaders();
 		fooHeaders.setContentType(MediaType.TEXT_PLAIN);
 		ClassPathResource fooResource = new ClassPathResource("org/springframework/http/codec/multipart/foo.txt");
@@ -102,7 +80,12 @@ class MultipartHttpHandlerIntegrationTests extends AbstractHttpHandlerIntegratio
 		MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
 		parts.add("fooPart", fooPart);
 		parts.add("barPart", barPart);
-		return parts;
+
+		URI url = URI.create("http://localhost:" + port + "/form-parts");
+		ResponseEntity<Void> response = new RestTemplate().exchange(
+				RequestEntity.post(url).contentType(mediaType).body(parts), Void.class);
+
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
 	}