HttpMessageConverters should support streaming

All HttpMessageConverters should support StreamingHttpOutputMessage.
Specifically, the BufferedImageHttpMessageConverter and
FormHttpMessageConverter should do so.

Issue: SPR-12715

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

@@ -38,9 +38,11 @@ import javax.imageio.stream.ImageOutputStream;
 import javax.imageio.stream.MemoryCacheImageInputStream;
 import javax.imageio.stream.MemoryCacheImageOutputStream;
 
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.HttpOutputMessage;
 import org.springframework.http.MediaType;
+import org.springframework.http.StreamingHttpOutputMessage;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -203,7 +205,30 @@ public class BufferedImageHttpMessageConverter implements HttpMessageConverter<B
 	}
 
 	@Override
-	public void write(BufferedImage image, MediaType contentType, HttpOutputMessage outputMessage)
+	public void write(final BufferedImage image, final MediaType contentType,
+			final HttpOutputMessage outputMessage)
+			throws IOException, HttpMessageNotWritableException {
+
+		if (outputMessage instanceof StreamingHttpOutputMessage) {
+			StreamingHttpOutputMessage streamingOutputMessage =
+					(StreamingHttpOutputMessage) outputMessage;
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				@Override
+				public void writeTo(OutputStream outputStream) throws IOException {
+					writeInternal(image, contentType, outputMessage.getHeaders(),
+							outputStream);
+				}
+			});
+
+		}
+		else {
+			writeInternal(image, contentType, outputMessage.getHeaders(),
+					outputMessage.getBody());
+		}
+	}
+
+	private void writeInternal(BufferedImage image, MediaType contentType,
+			HttpHeaders headers, OutputStream body)
 			throws IOException, HttpMessageNotWritableException {
 
 		if (contentType == null || contentType.isWildcardType() || contentType.isWildcardSubtype()) {
@@ -211,16 +236,16 @@ public class BufferedImageHttpMessageConverter implements HttpMessageConverter<B
 		}
 		Assert.notNull(contentType,
 				"Count not determine Content-Type, set one using the 'defaultContentType' property");
-		outputMessage.getHeaders().setContentType(contentType);
+		headers.setContentType(contentType);
 		ImageOutputStream imageOutputStream = null;
 		ImageWriter imageWriter = null;
 		try {
-			imageOutputStream = createImageOutputStream(outputMessage.getBody());
 			Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByMIMEType(contentType.toString());
 			if (imageWriters.hasNext()) {
 				imageWriter = imageWriters.next();
 				ImageWriteParam iwp = imageWriter.getDefaultWriteParam();
 				process(iwp);
+				imageOutputStream = createImageOutputStream(body);
 				imageWriter.setOutput(imageOutputStream);
 				imageWriter.write(null, new IIOImage(image, null, null), iwp);
 			}

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

@@ -36,6 +36,7 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.HttpOutputMessage;
 import org.springframework.http.MediaType;
+import org.springframework.http.StreamingHttpOutputMessage;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -286,20 +287,47 @@ public class FormHttpMessageConverter implements HttpMessageConverter<MultiValue
 				builder.append('&');
 			}
 		}
-		byte[] bytes = builder.toString().getBytes(charset.name());
+		final byte[] bytes = builder.toString().getBytes(charset.name());
 		outputMessage.getHeaders().setContentLength(bytes.length);
-		StreamUtils.copy(bytes, outputMessage.getBody());
+
+		if (outputMessage instanceof StreamingHttpOutputMessage) {
+			StreamingHttpOutputMessage streamingOutputMessage =
+					(StreamingHttpOutputMessage) outputMessage;
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				@Override
+				public void writeTo(OutputStream outputStream) throws IOException {
+					StreamUtils.copy(bytes, outputStream);
+				}
+			});
+		}
+		else {
+			StreamUtils.copy(bytes, outputMessage.getBody());
+		}
 	}
 
-	private void writeMultipart(MultiValueMap<String, Object> parts, HttpOutputMessage outputMessage) throws IOException {
-		byte[] boundary = generateMultipartBoundary();
+	private void writeMultipart(final MultiValueMap<String, Object> parts, HttpOutputMessage outputMessage) throws IOException {
+		final byte[] boundary = generateMultipartBoundary();
 		Map<String, String> parameters = Collections.singletonMap("boundary", new String(boundary, "US-ASCII"));
 
 		MediaType contentType = new MediaType(MediaType.MULTIPART_FORM_DATA, parameters);
-		outputMessage.getHeaders().setContentType(contentType);
-
-		writeParts(outputMessage.getBody(), parts, boundary);
-		writeEnd(outputMessage.getBody(), boundary);
+		HttpHeaders headers = outputMessage.getHeaders();
+		headers.setContentType(contentType);
+
+		if (outputMessage instanceof StreamingHttpOutputMessage) {
+			StreamingHttpOutputMessage streamingOutputMessage =
+					(StreamingHttpOutputMessage) outputMessage;
+			streamingOutputMessage.setBody(new StreamingHttpOutputMessage.Body() {
+				@Override
+				public void writeTo(OutputStream outputStream) throws IOException {
+					writeParts(outputStream, parts, boundary);
+					writeEnd(outputStream, boundary);
+				}
+			});
+		}
+		else {
+			writeParts(outputMessage.getBody(), parts, boundary);
+			writeEnd(outputMessage.getBody(), boundary);
+		}
 	}
 
 	private void writeParts(OutputStream os, MultiValueMap<String, Object> parts, byte[] boundary) throws IOException {

spring-web/src/test/java/org/springframework/web/client/AbstractJettyServerTestCase.java

@@ -19,6 +19,7 @@ package org.springframework.web.client;
 import java.io.IOException;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import javax.servlet.GenericServlet;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
@@ -85,6 +86,7 @@ public class AbstractJettyServerTestCase {
 		handler.addServlet(new ServletHolder(new ErrorServlet(500)), "/status/server");
 		handler.addServlet(new ServletHolder(new UriServlet()), "/uri/*");
 		handler.addServlet(new ServletHolder(new MultipartServlet()), "/multipart");
+		handler.addServlet(new ServletHolder(new FormServlet()), "/form");
 		handler.addServlet(new ServletHolder(new DeleteServlet()), "/delete");
 		handler.addServlet(
 				new ServletHolder(new PutServlet(helloWorld, bytes, textContentType)),
@@ -286,6 +288,28 @@ public class AbstractJettyServerTestCase {
 		}
 	}
 
+	@SuppressWarnings("serial")
+	private static class FormServlet extends HttpServlet {
+
+		@Override
+		protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+			assertEquals(MediaType.APPLICATION_FORM_URLENCODED_VALUE,
+					req.getContentType());
+
+			Map<String, String[]> parameters = req.getParameterMap();
+			assertEquals(2, parameters.size());
+
+			String[] values = parameters.get("name 1");
+			assertEquals(1, values.length);
+			assertEquals("value 1", values[0]);
+
+			values = parameters.get("name 2");
+			assertEquals(2, values.length);
+			assertEquals("value 2+1", values[0]);
+			assertEquals("value 2+2", values[1]);
+		}
+	}
+
 	@SuppressWarnings("serial")
 	private static class DeleteServlet extends HttpServlet {
 

spring-web/src/test/java/org/springframework/web/client/RestTemplateIntegrationTests.java

@@ -179,6 +179,16 @@ public class RestTemplateIntegrationTests extends AbstractJettyServerTestCase {
 		template.postForLocation(baseUrl + "/multipart", parts);
 	}
 
+	@Test
+	public void form() throws UnsupportedEncodingException {
+		MultiValueMap<String, String> form = new LinkedMultiValueMap<String, String>();
+		form.add("name 1", "value 1");
+		form.add("name 2", "value 2+1");
+		form.add("name 2", "value 2+2");
+
+		template.postForLocation(baseUrl + "/form", form);
+	}
+
 	@Test
 	public void exchangeGet() throws Exception {
 		HttpHeaders requestHeaders = new HttpHeaders();