Add MultipartFileArgumentResolver for HTTP interface client

spring-web/src/main/java/org/springframework/web/service/invoker/HttpServiceProxyFactory.java

@@ -252,6 +252,7 @@ private List<HttpServiceArgumentResolver> initArgumentResolvers() {
 			// Specific type
 			resolvers.add(new UrlArgumentResolver());
 			resolvers.add(new HttpMethodArgumentResolver());
+			resolvers.add(new MultipartFileArgumentResolver());
 
 			return resolvers;
 		}

spring-web/src/main/java/org/springframework/web/service/invoker/MultipartFileArgumentResolver.java

@@ -0,0 +1,70 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.service.invoker;
+
+import java.util.Optional;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.core.io.Resource;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.util.Assert;
+import org.springframework.web.multipart.MultipartFile;
+
+/**
+ * {@link HttpServiceArgumentResolver} for arguments of type {@link MultipartFile}.
+ * The arguments should not be annotated. To allow for non-required arguments,
+ * the {@link MultipartFile} parameters can also be wrapped with {@link Optional}.
+ *
+ * @author Olga Maciaszek-Sharma
+ * @since 6.1
+ */
+public class MultipartFileArgumentResolver extends AbstractNamedValueArgumentResolver {
+
+	private static final String MULTIPART_FILE_LABEL = "multipart file";
+
+	@Override
+	protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
+		if (!parameter.nestedIfOptional().getNestedParameterType().equals(MultipartFile.class)) {
+			return null;
+		}
+		return new NamedValueInfo("", true, null, MULTIPART_FILE_LABEL, true);
+
+	}
+
+	@Override
+	protected void addRequestValue(String name, Object value, MethodParameter parameter,
+			HttpRequestValues.Builder requestValues) {
+		Assert.state(value instanceof MultipartFile,
+				"The value has to be of type 'MultipartFile'");
+
+		MultipartFile file = (MultipartFile) value;
+		requestValues.addRequestPart(name, toHttpEntity(name, file));
+	}
+
+	private HttpEntity<Resource> toHttpEntity(String name, MultipartFile file) {
+		HttpHeaders headers = new HttpHeaders();
+		if (file.getOriginalFilename() != null) {
+			headers.setContentDispositionFormData(name, file.getOriginalFilename());
+		}
+		if (file.getContentType() != null) {
+			headers.add(HttpHeaders.CONTENT_TYPE, file.getContentType());
+		}
+		return new HttpEntity<>(file.getResource(), headers);
+	}
+
+}

spring-web/src/test/java/org/springframework/web/service/invoker/MultipartFileArgumentResolverTests.java

@@ -0,0 +1,101 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.service.invoker;
+
+import java.util.Optional;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.http.ContentDisposition;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.util.MultiValueMap;
+import org.springframework.web.bind.annotation.RequestPart;
+import org.springframework.web.multipart.MultipartFile;
+import org.springframework.web.service.annotation.PostExchange;
+import org.springframework.web.testfixture.servlet.MockMultipartFile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link MultipartFileArgumentResolver}.
+ * Tests for base class functionality of this resolver can be found in {@link NamedValueArgumentResolverTests}.
+ *
+ * @author Olga Maciaszek-Sharma
+ */
+@SuppressWarnings("unchecked")
+class MultipartFileArgumentResolverTests {
+
+	private final TestHttpClientAdapter clientAdapter = new TestHttpClientAdapter();
+
+	private TestClient client;
+
+	@BeforeEach
+	void setUp() {
+		HttpServiceProxyFactory proxyFactory = HttpServiceProxyFactory.builder(this.clientAdapter).build();
+		this.client = proxyFactory.createClient(TestClient.class);
+	}
+
+	@Test
+	void multipartFile() {
+		String fileName = "testFileName";
+		String originalFileName = "originalTestFileName";
+		MultipartFile testFile = new MockMultipartFile(fileName, originalFileName,
+				MediaType.APPLICATION_JSON_VALUE, "test".getBytes());
+		this.client.postMultipartFile(testFile);
+
+		Object body = clientAdapter.getRequestValues().getBodyValue();
+
+		assertThat(body).isInstanceOf(MultiValueMap.class);
+		MultiValueMap<String, HttpEntity<?>> map = (MultiValueMap<String, HttpEntity<?>>) body;
+		assertThat(map.size()).isEqualTo(1);
+		assertThat(map.getFirst("file")).isNotNull();
+		HttpEntity<?> fileEntity = map.getFirst("file");
+		assertThat(fileEntity.getBody()).isEqualTo(testFile.getResource());
+		HttpHeaders headers = fileEntity.getHeaders();
+		assertThat(headers.getContentType()).isEqualTo(MediaType.APPLICATION_JSON);
+		ContentDisposition contentDisposition = headers.getContentDisposition();
+		assertThat(contentDisposition.getType()).isEqualTo("form-data");
+		assertThat(contentDisposition.getName()).isEqualTo("file");
+		assertThat(contentDisposition.getFilename()).isEqualTo(originalFileName);
+	}
+
+	@Test
+	void optionalMultipartFile() {
+		this.client.postOptionalMultipartFile(Optional.empty(), "anotherPart");
+
+		Object body = clientAdapter.getRequestValues().getBodyValue();
+
+		assertThat(body).isInstanceOf(MultiValueMap.class);
+		MultiValueMap<String, HttpEntity<?>> map = (MultiValueMap<String, HttpEntity<?>>) body;
+		assertThat(map.size()).isEqualTo(1);
+		assertThat(map.getFirst("anotherPart")).isNotNull();
+	}
+
+	@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+	private interface TestClient {
+
+		@PostExchange
+		void postMultipartFile(MultipartFile file);
+
+		@PostExchange
+		void postOptionalMultipartFile(Optional<MultipartFile> file, @RequestPart String anotherPart);
+
+	}
+}

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 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 @@
  * using {@link WebClient} and {@link MockWebServer}.
  *
  * @author Rossen Stoyanchev
+ * @author Olga Maciaszek-Sharma
  */
 public class WebClientHttpServiceProxyTests {
 
@@ -133,6 +138,25 @@ void formData() throws Exception {
 		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 @@ private interface TestHttpService {
 		@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);
+
 	}
 
 }