Add MultipartFile support to HTTP interface client

See gh-30728

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/support/WebClientHttpServiceProxyTests.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.
@@ -33,16 +33,20 @@ import org.junit.jupiter.api.Test;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
+import org.springframework.http.MediaType;
 import org.springframework.lang.Nullable;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestAttribute;
 import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RequestPart;
+import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.service.annotation.GetExchange;
 import org.springframework.web.service.annotation.PostExchange;
 import org.springframework.web.service.invoker.HttpServiceProxyFactory;
+import org.springframework.web.testfixture.servlet.MockMultipartFile;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -52,6 +56,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * using {@link WebClient} and {@link MockWebServer}.
  *
  * @author Rossen Stoyanchev
+ * @author Olga Maciaszek-Sharma
  */
 public class WebClientHttpServiceProxyTests {
 
@@ -133,6 +138,25 @@ public class WebClientHttpServiceProxyTests {
 		assertThat(request.getBody().readUtf8()).isEqualTo("param1=value+1&param2=value+2");
 	}
 
+	@Test // gh-30342
+	void multipart() throws InterruptedException {
+		prepareResponse(response -> response.setResponseCode(201));
+		String fileName = "testFileName";
+		String originalFileName = "originalTestFileName";
+		MultipartFile file = new MockMultipartFile(fileName, originalFileName,
+				MediaType.APPLICATION_JSON_VALUE, "test".getBytes());
+
+		initHttpService().postMultipart(file, "test2");
+
+		RecordedRequest request = this.server.takeRequest();
+		assertThat(request.getHeaders().get("Content-Type")).startsWith("multipart/form-data;boundary=");
+		assertThat(request.getBody().readUtf8())
+				.containsSubsequence("Content-Disposition: form-data; name=\"file\"; filename=\"originalTestFileName\"",
+						"Content-Type: application/json", "Content-Length: 4", "test",
+						"Content-Disposition: form-data; name=\"anotherPart\"",
+						"Content-Type: text/plain;charset=UTF-8", "Content-Length: 5", "test2");
+	}
+
 	private TestHttpService initHttpService() {
 		WebClient webClient = WebClient.builder().baseUrl(this.server.url("/").toString()).build();
 		return initHttpService(webClient);
@@ -166,6 +190,9 @@ public class WebClientHttpServiceProxyTests {
 		@PostExchange(contentType = "application/x-www-form-urlencoded")
 		void postForm(@RequestParam MultiValueMap<String, String> params);
 
+		@PostExchange(contentType = MediaType.MULTIPART_FORM_DATA_VALUE)
+		void postMultipart(MultipartFile file, @RequestPart String anotherPart);
+
 	}
 
 }