Add MultipartFile support to HTTP interface client

See gh-30728

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);
+
+	}
+}