Allow client-side use of BodyExtractors#toFormData

Issue: SPR-16804

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyExtractors.java

@@ -165,19 +165,22 @@ private static <T> Flux<T> permitEmptyOrFail(ReactiveHttpInputMessage message, U
 
 	/**
 	 * Return a {@code BodyExtractor} that reads form data into a {@link MultiValueMap}.
+	 * <p>As of 5.1 this method can also be used on the client side to read form
+	 * data from a server response (e.g. OAuth).
 	 * @return a {@code BodyExtractor} that reads form data
 	 */
-	// Note that the returned BodyExtractor is parameterized to ServerHttpRequest, not
-	// ReactiveHttpInputMessage like other methods, since reading form data only typically happens on
-	// the server-side
-	public static BodyExtractor<Mono<MultiValueMap<String, String>>, ServerHttpRequest> toFormData() {
-		return (request, context) -> {
+	public static BodyExtractor<Mono<MultiValueMap<String, String>>, ReactiveHttpInputMessage> toFormData() {
+		return (message, context) -> {
 			ResolvableType type = FORM_MAP_TYPE;
 			HttpMessageReader<MultiValueMap<String, String>> reader =
 					messageReader(type, MediaType.APPLICATION_FORM_URLENCODED, context);
-			return context.serverResponse()
-					.map(response -> reader.readMono(type, type, request, response, context.hints()))
-					.orElseGet(() -> reader.readMono(type, request, context.hints()));
+			Optional<ServerHttpResponse> response = context.serverResponse();
+			if (response.isPresent() && message instanceof ServerHttpRequest) {
+				return reader.readMono(type, type, (ServerHttpRequest) message, response.get(), context.hints());
+			}
+			else {
+				return reader.readMono(type, message, context.hints());
+			}
 		};
 	}
 

spring-webflux/src/test/java/org/springframework/web/reactive/function/BodyExtractorsTests.java

@@ -107,7 +107,7 @@ public Map<String, Object> hints() {
 
 
 	@Test
-	public void toMono() throws Exception {
+	public void toMono() {
 		BodyExtractor<Mono<String>, ReactiveHttpInputMessage> extractor = BodyExtractors.toMono(String.class);
 
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
@@ -125,7 +125,7 @@ public void toMono() throws Exception {
 	}
 
 	@Test
-	public void toMonoParameterizedTypeReference() throws Exception {
+	public void toMonoParameterizedTypeReference() {
 		BodyExtractor<Mono<Map<String, String>>, ReactiveHttpInputMessage> extractor =
 				BodyExtractors.toMono(new ParameterizedTypeReference<Map<String, String>>() {});
 
@@ -147,7 +147,7 @@ public void toMonoParameterizedTypeReference() throws Exception {
 	}
 
 	@Test
-	public void toMonoWithHints() throws Exception {
+	public void toMonoWithHints() {
 		BodyExtractor<Mono<User>, ReactiveHttpInputMessage> extractor = BodyExtractors.toMono(User.class);
 		this.hints.put(JSON_VIEW_HINT, SafeToDeserialize.class);
 
@@ -172,7 +172,7 @@ public void toMonoWithHints() throws Exception {
 	}
 
 	@Test // SPR-15758
-	public void toMonoWithEmptyBodyAndNoContentType() throws Exception {
+	public void toMonoWithEmptyBodyAndNoContentType() {
 		BodyExtractor<Mono<Map<String, String>>, ReactiveHttpInputMessage> extractor =
 				BodyExtractors.toMono(new ParameterizedTypeReference<Map<String, String>>() {});
 
@@ -183,7 +183,7 @@ public void toMonoWithEmptyBodyAndNoContentType() throws Exception {
 	}
 
 	@Test
-	public void toFlux() throws Exception {
+	public void toFlux() {
 		BodyExtractor<Flux<String>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(String.class);
 
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
@@ -201,7 +201,7 @@ public void toFlux() throws Exception {
 	}
 
 	@Test
-	public void toFluxWithHints() throws Exception {
+	public void toFluxWithHints() {
 		BodyExtractor<Flux<User>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(User.class);
 		this.hints.put(JSON_VIEW_HINT, SafeToDeserialize.class);
 
@@ -230,7 +230,7 @@ public void toFluxWithHints() throws Exception {
 	}
 
 	@Test
-	public void toFluxUnacceptable() throws Exception {
+	public void toFluxUnacceptable() {
 		BodyExtractor<Flux<String>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(String.class);
 
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
@@ -266,9 +266,7 @@ public Map<String, Object> hints() {
 	}
 
 	@Test
-	public void toFormData() throws Exception {
-		BodyExtractor<Mono<MultiValueMap<String, String>>, ServerHttpRequest> extractor = BodyExtractors.toFormData();
-
+	public void toFormData() {
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
 		String text = "name+1=value+1&name+2=value+2%2B1&name+2=value+2%2B2&name+3";
 		DefaultDataBuffer dataBuffer = factory.wrap(ByteBuffer.wrap(text.getBytes(StandardCharsets.UTF_8)));
@@ -278,7 +276,7 @@ public void toFormData() throws Exception {
 				.contentType(MediaType.APPLICATION_FORM_URLENCODED)
 				.body(body);
 
-		Mono<MultiValueMap<String, String>> result = extractor.extract(request, this.context);
+		Mono<MultiValueMap<String, String>> result = BodyExtractors.toFormData().extract(request, this.context);
 
 		StepVerifier.create(result)
 				.consumeNextWith(form -> {
@@ -295,7 +293,7 @@ public void toFormData() throws Exception {
 	}
 
 	@Test
-	public void toParts() throws Exception {
+	public void toParts() {
 		BodyExtractor<Flux<Part>, ServerHttpRequest> extractor = BodyExtractors.toParts();
 
 		String bodyContents = "-----------------------------9051914041544843365972754266\r\n" +
@@ -353,7 +351,7 @@ public void toParts() throws Exception {
 	}
 
 	@Test
-	public void toDataBuffers() throws Exception {
+	public void toDataBuffers() {
 		BodyExtractor<Flux<DataBuffer>, ReactiveHttpInputMessage> extractor = BodyExtractors.toDataBuffers();
 
 		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();