Fix multi-part form handling for WebFlux apps

In WebFlux (but not MVC) you have to explicitly ask for the multi-
part content separately from the form data.

Fixes gh-223

spring-cloud-function-samples/function-sample-pojo/src/test/java/com/example/SampleApplicationTests.java

@@ -92,7 +92,7 @@ public class SampleApplicationTests {
 	}
 
 	@Test
-	@Ignore
+	// @Ignore
 	public void multipart() throws Exception {
 
 		LinkedMultiValueMap<String, String> map = new LinkedMultiValueMap<>();

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/flux/FunctionController.java

@@ -27,7 +27,11 @@ import org.springframework.cloud.function.web.RequestProcessor.FunctionWrapper;
 import org.springframework.cloud.function.web.constants.WebRequestConstants;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
+import org.springframework.http.codec.multipart.FormFieldPart;
+import org.springframework.http.codec.multipart.Part;
 import org.springframework.stereotype.Component;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -49,13 +53,34 @@ public class FunctionController {
 		this.processor = processor;
 	}
 
-	@PostMapping(path = "/**", consumes = { MediaType.APPLICATION_FORM_URLENCODED_VALUE,
+	@PostMapping(path = "/**", consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE)
-			MediaType.MULTIPART_FORM_DATA_VALUE })
 	@ResponseBody
 	public Mono<ResponseEntity<?>> form(ServerWebExchange request) {
 		FunctionWrapper wrapper = wrapper(request);
 		return request.getFormData().doOnSuccess(params -> wrapper.params(params))
-				.then(processor.post(wrapper, null, false));
+				.then(Mono.defer(() -> processor.post(wrapper, null, false)));
+	}
+
+	@PostMapping(path = "/**", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
+	@ResponseBody
+	public Mono<ResponseEntity<?>> multipart(ServerWebExchange request) {
+		FunctionWrapper wrapper = wrapper(request);
+		return request.getMultipartData()
+				.doOnSuccess(params -> wrapper.params(multi(params)))
+				.then(Mono.defer(() -> processor.post(wrapper, null, false)));
+	}
+
+	private MultiValueMap<String, String> multi(MultiValueMap<String, Part> body) {
+		MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
+		for (String key : body.keySet()) {
+			for (Part part : body.get(key)) {
+				if (part instanceof FormFieldPart) {
+					FormFieldPart form = (FormFieldPart) part;
+					map.add(key, form.value());
+				}
+			}
+		}
+		return map;
 	}
 
 	@PostMapping(path = "/**")

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/flux/HttpPostIntegrationTests.java

@@ -302,7 +302,6 @@ public class HttpPostIntegrationTests {
 	}
 
 	@Test
-	@Ignore
 	public void multipart() throws Exception {
 
 		LinkedMultiValueMap<String, String> map = new LinkedMultiValueMap<>();

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/HttpPostIntegrationTests.java

@@ -307,6 +307,20 @@ public class HttpPostIntegrationTests {
 				String.class).getBody()).isEqualTo("[{\"A\":6,\"B\":11}]");
 	}
 
+	@Test
+	public void multipart() throws Exception {
+
+		LinkedMultiValueMap<String, String> map = new LinkedMultiValueMap<>();
+
+		map.put("A", Arrays.asList("1", "2", "3"));
+		map.put("B", Arrays.asList("5", "6"));
+
+		assertThat(rest.exchange(
+				RequestEntity.post(new URI("/sum")).accept(MediaType.APPLICATION_JSON)
+						.contentType(MediaType.MULTIPART_FORM_DATA).body(map),
+				String.class).getBody()).isEqualTo("[{\"A\":6,\"B\":11}]");
+	}
+
 	@Test
 	public void count() throws Exception {
 		List<String> list = Arrays.asList("A", "B", "A");