Support writing multipart non-ASCII file names

Issue: SPR-12108

build.gradle

@@ -684,6 +684,7 @@ project("spring-web") {
 		optional("log4j:log4j:1.2.17")
 		optional("com.googlecode.protobuf-java-format:protobuf-java-format:1.2")
 		optional("com.google.protobuf:protobuf-java:${protobufVersion}")
+		optional("javax.mail:javax.mail-api:1.5.2")
 		testCompile(project(":spring-context-support"))  // for JafMediaTypeFactory
 		testCompile("xmlunit:xmlunit:1.5")
 		testCompile("org.slf4j:slf4j-jcl:${slf4jVersion}")

spring-web/src/main/java/org/springframework/http/converter/FormHttpMessageConverter.java

@@ -41,6 +41,8 @@ import org.springframework.util.MultiValueMap;
 import org.springframework.util.StreamUtils;
 import org.springframework.util.StringUtils;
 
+import javax.mail.internet.MimeUtility;
+
 /**
  * Implementation of {@link HttpMessageConverter} to read and write 'normal' HTML
  * forms and also to write (but not read) multipart data (e.g. file uploads).
@@ -92,6 +94,8 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 
 	private Charset charset = Charset.forName("UTF-8");
 
+	private Charset multipartCharset;
+
 	private List<MediaType> supportedMediaTypes = new ArrayList<MediaType>();
 
 	private List<HttpMessageConverter<?>> partConverters = new ArrayList<HttpMessageConverter<?>>();
@@ -118,6 +122,18 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 		this.charset = charset;
 	}
 
+	/**
+	 * Set the character set to use when writing multipart data to encode file
+	 * names. Encoding is based on the encoded-word syntax defined in RFC 2047
+	 * and relies on the MimeUtility class from "javax.mail-api".
+	 * <p>If not set file names will be encoded as US-ASCII.
+	 * @param multipartCharset the charset to use
+	 * @see <a href="http://en.wikipedia.org/wiki/MIME#Encoded-Word">Encoded-Word</a>
+	 */
+	public void setMultipartCharset(Charset multipartCharset) {
+		this.multipartCharset = multipartCharset;
+	}
+
 	/**
 	 * Set the list of {@link MediaType} objects supported by this converter.
 	 */
@@ -374,7 +390,17 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 	protected String getFilename(Object part) {
 		if (part instanceof Resource) {
 			Resource resource = (Resource) part;
-			return resource.getFilename();
+			String filename = resource.getFilename();
+			if (multipartCharset != null) {
+				try {
+					filename = MimeUtility.encodeText(filename, multipartCharset.name(), null);
+				}
+				catch (UnsupportedEncodingException e) {
+					// should not happen
+					throw new IllegalStateException(e);
+				}
+			}
+			return filename;
 		}
 		else {
 			return null;

spring-web/src/test/java/org/springframework/http/converter/FormHttpMessageConverterTests.java

@@ -116,6 +116,17 @@ public class FormHttpMessageConverterTests {
 
 		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);
+
 		Source xml = new StreamSource(new StringReader("<root><child/></root>"));
 		HttpHeaders entityHeaders = new HttpHeaders();
 		entityHeaders.setContentType(MediaType.TEXT_XML);
@@ -123,6 +134,7 @@ public class FormHttpMessageConverterTests {
 		parts.add("xml", entity);
 
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		converter.setMultipartCharset(Charset.forName("UTF-8"));
 		converter.write(parts, MediaType.MULTIPART_FORM_DATA, outputMessage);
 
 		final MediaType contentType = outputMessage.getHeaders().getContentType();
@@ -132,7 +144,7 @@ public class FormHttpMessageConverterTests {
 		FileItemFactory fileItemFactory = new DiskFileItemFactory();
 		FileUpload fileUpload = new FileUpload(fileItemFactory);
 		List<FileItem> items = fileUpload.parseRequest(new MockHttpOutputMessageRequestContext(outputMessage));
-		assertEquals(5, items.size());
+		assertEquals(6, items.size());
 		FileItem item = items.get(0);
 		assertTrue(item.isFormField());
 		assertEquals("name 1", item.getFieldName());
@@ -156,6 +168,13 @@ public class FormHttpMessageConverterTests {
 		assertEquals(logo.getFile().length(), item.getSize());
 
 		item = items.get(4);
+		assertFalse(item.isFormField());
+		assertEquals("utf8", item.getFieldName());
+		assertEquals("Hall\u00F6le.jpg", item.getName());
+		assertEquals("image/jpeg", item.getContentType());
+		assertEquals(logo.getFile().length(), item.getSize());
+
+		item = items.get(5);
 		assertEquals("xml", item.getFieldName());
 		assertEquals("text/xml", item.getContentType());
 		verify(outputMessage.getBody(), never()).close();