GH-597 Add support for handling MultipartFile(s)

This initial fix ensures that functions can process single MultipartFile as well as multiple.

Resolves #597

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

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2012-2019 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.cloud.function.web.mvc;
+
+import java.net.URI;
+import java.util.List;
+import java.util.function.Function;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.cloud.function.json.JsonMapper;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.SocketUtils;
+import org.springframework.web.multipart.MultipartFile;
+
+import static org.assertj.core.api.Assertions.assertThat;
+/**
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+public class MultipartFileTests {
+
+	@BeforeEach
+	public void init() throws Exception {
+		String port = "" + SocketUtils.findAvailableTcpPort();
+		System.setProperty("server.port", port);
+	}
+
+	@AfterEach
+	public void close() throws Exception {
+		System.clearProperty("server.port");
+	}
+
+	@Test
+	public void testMultipartFileUpload() throws Exception {
+		ApplicationContext context = SpringApplication.run(TestConfiguration.class);
+		JsonMapper mapper = context.getBean(JsonMapper.class);
+		TestRestTemplate template = new TestRestTemplate();
+		String port = System.getProperty("server.port");
+
+		LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
+		map.add("file", new ClassPathResource("META-INF/spring.factories"));
+		HttpHeaders headers = new HttpHeaders();
+		headers.setContentType(MediaType.MULTIPART_FORM_DATA);
+
+		HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<LinkedMultiValueMap<String, Object>>(
+				map, headers);
+		ResponseEntity<String> result = template.exchange(new URI("http://localhost:" + port + "/uppercase"),
+				HttpMethod.POST, requestEntity, String.class);
+		List<String> resultCollection = mapper.fromJson(result.getBody(), List.class);
+		assertThat(resultCollection.get(0)).isEqualTo("SPRING.FACTORIES");
+	}
+
+	@Test
+	public void testMultipartFilesUpload() throws Exception {
+		ApplicationContext context = SpringApplication.run(TestConfiguration.class);
+		JsonMapper mapper = context.getBean(JsonMapper.class);
+		TestRestTemplate template = new TestRestTemplate();
+		String port = System.getProperty("server.port");
+
+		LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
+		map.add("fileA", new ClassPathResource("META-INF/spring.factories"));
+		map.add("fileB", new ClassPathResource("static/test.html"));
+		HttpHeaders headers = new HttpHeaders();
+		headers.setContentType(MediaType.MULTIPART_FORM_DATA);
+
+		HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<LinkedMultiValueMap<String, Object>>(
+				map, headers);
+		ResponseEntity<String> result = template.exchange(new URI("http://localhost:" + port + "/uppercase"),
+				HttpMethod.POST, requestEntity, String.class);
+		List<String> resultCollection = mapper.fromJson(result.getBody(), List.class);
+		assertThat(resultCollection.get(0)).isEqualTo("SPRING.FACTORIES");
+		assertThat(resultCollection.get(1)).isEqualTo("TEST.HTML");
+	}
+
+	@EnableAutoConfiguration
+	protected static class TestConfiguration {
+
+		@Bean
+		public Function<MultipartFile, String> uppercase() {
+			return value -> {
+				return value.getOriginalFilename().toUpperCase();
+			};
+		}
+	}
+}