Add MultipartFile support to HTTP interface client

See gh-30728

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

@@ -252,6 +252,7 @@ public final class HttpServiceProxyFactory {
 			// 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);
+	}
+
+}