Add MultipartHttpMessageWriter

This commit adds a reactive HttpMessageWriter that allows
to write multipart HTML forms with multipart/form-data
media type.

Issue: SPR-14546

spring-web/src/test/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriterTests.java

@@ -0,0 +1,168 @@
+/*
+ * Copyright 2002-2017 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
+ *
+ *      http://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.http.codec.multipart;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import org.junit.Test;
+import static org.springframework.http.HttpHeaders.CONTENT_TYPE;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.CharSequenceEncoder;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+import org.springframework.http.HttpEntity;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.EncoderHttpMessageWriter;
+import org.springframework.http.codec.ResourceHttpMessageWriter;
+import org.springframework.http.codec.json.Jackson2JsonEncoder;
+import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
+import org.springframework.mock.http.server.reactive.test.MockServerHttpResponse;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * @author Sebastien Deleuze
+ */
+public class MultipartHttpMessageWriterTests {
+
+	private final MultipartHttpMessageWriter writer = new MultipartHttpMessageWriter(
+			Arrays.asList(
+				new EncoderHttpMessageWriter<>(CharSequenceEncoder.textPlainOnly()),
+				new ResourceHttpMessageWriter(),
+				new EncoderHttpMessageWriter<>(new Jackson2JsonEncoder())
+	));
+
+	@Test
+	public void canWrite() {
+		assertTrue(this.writer.canWrite(ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, Object.class),
+				MediaType.MULTIPART_FORM_DATA));
+		assertTrue(this.writer.canWrite(ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class),
+				MediaType.MULTIPART_FORM_DATA));
+		assertFalse(this.writer.canWrite(ResolvableType.forClassWithGenerics(MultiValueMap.class, Object.class, Object.class),
+				MediaType.MULTIPART_FORM_DATA));
+		assertFalse(this.writer.canWrite(ResolvableType.forClassWithGenerics(Map.class, String.class, Object.class),
+				MediaType.MULTIPART_FORM_DATA));
+		assertFalse(this.writer.canWrite(ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, Object.class),
+				MediaType.APPLICATION_FORM_URLENCODED));
+	}
+
+	@Test
+	public void writeMultipart() throws Exception {
+		MultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
+		parts.add("name 1", "value 1");
+		parts.add("name 2", "value 2+1");
+		parts.add("name 2", "value 2+2");
+
+		Resource logo = new ClassPathResource("/org/springframework/http/converter/logo.jpg");
+		parts.add("logo", logo);
+
+		// SPR-12108
+		Resource utf8 = new ClassPathResource("/org/springframework/http/converter/logo.jpg") {
+			@Override
+			public String getFilename() {
+				return "Hall\u00F6le.jpg";
+			}
+		};
+		parts.add("utf8", utf8);
+
+		Foo foo = new Foo("bar");
+		HttpHeaders entityHeaders = new HttpHeaders();
+		entityHeaders.setContentType(MediaType.APPLICATION_JSON_UTF8);
+		HttpEntity<Foo> entity = new HttpEntity<>(foo, entityHeaders);
+		parts.add("json", entity);
+
+		MockServerHttpResponse response = new MockServerHttpResponse();
+		this.writer.write(Mono.just(parts), null, MediaType.MULTIPART_FORM_DATA, response, Collections.emptyMap()).block();
+
+		final MediaType contentType = response.getHeaders().getContentType();
+		assertNotNull("No boundary found", contentType.getParameter("boundary"));
+
+		// see if NIO Multipart can read what we wrote
+		MultipartHttpMessageReader multipartReader = new SynchronossMultipartHttpMessageReader();
+		MockServerHttpRequest request = MockServerHttpRequest.post("/foo")
+				.header(CONTENT_TYPE, contentType.toString())
+				.body(response.getBody());
+
+		MultiValueMap<String, Part> requestParts = multipartReader.
+				readMono(MultipartHttpMessageReader.MULTIPART_VALUE_TYPE, request, Collections.emptyMap()).block();
+		assertEquals(5, requestParts.size());
+
+
+		Part part = requestParts.getFirst("name 1");
+		assertEquals("name 1", part.getName());
+		assertEquals("value 1", part.getContentAsString().block());
+		assertFalse(part.getFilename().isPresent());
+
+		List<Part> part2 = requestParts.get("name 2");
+		assertEquals(2, part2.size());
+		part = part2.get(0);
+		assertEquals("name 2", part.getName());
+		assertEquals("value 2+1", part.getContentAsString().block());
+		part = part2.get(1);
+		assertEquals("name 2", part.getName());
+		assertEquals("value 2+2", part.getContentAsString().block());
+
+		part = requestParts.getFirst("logo");
+		assertEquals("logo", part.getName());
+		assertTrue(part.getFilename().isPresent());
+		assertEquals("logo.jpg", part.getFilename().get());
+		assertEquals(MediaType.IMAGE_JPEG, part.getHeaders().getContentType());
+		assertEquals(logo.getFile().length(), part.getHeaders().getContentLength());
+
+		part = requestParts.getFirst("utf8");
+		assertEquals("utf8", part.getName());
+		assertTrue(part.getFilename().isPresent());
+		assertEquals("Hall\u00F6le.jpg", part.getFilename().get());
+		assertEquals(MediaType.IMAGE_JPEG, part.getHeaders().getContentType());
+		assertEquals(utf8.getFile().length(), part.getHeaders().getContentLength());
+
+		part = requestParts.getFirst("json");
+		assertEquals("json", part.getName());
+		assertEquals(MediaType.APPLICATION_JSON_UTF8, part.getHeaders().getContentType());
+		assertEquals("{\"bar\":\"bar\"}", part.getContentAsString().block());
+	}
+
+	private class Foo {
+
+		private String bar;
+
+		public Foo() {
+		}
+
+		public Foo(String bar) {
+			this.bar = bar;
+		}
+
+		public String getBar() {
+			return bar;
+		}
+
+		public void setBar(String bar) {
+			this.bar = bar;
+		}
+	}
+
+}