BufferedImage converter writes Content-Type again

Issue: SPR-13906

spring-web/src/test/java/org/springframework/http/MockHttpOutputMessage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -21,10 +21,11 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.charset.Charset;
 
-import static org.mockito.Mockito.*;
+import static org.mockito.Mockito.spy;
 
 /**
  * @author Arjen Poutsma
+ * @author Rossen Stoyanchev
  */
 public class MockHttpOutputMessage implements HttpOutputMessage {
 
@@ -34,19 +35,31 @@ public class MockHttpOutputMessage implements HttpOutputMessage {
 
 	private boolean headersWritten = false;
 
+	private final HttpHeaders writtenHeaders = new HttpHeaders();
+
+
 	@Override
 	public HttpHeaders getHeaders() {
 		return (this.headersWritten ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
 	}
 
+	/**
+	 * Return a copy of the actual headers written at the time of the call to
+	 * getBody, i.e. ignoring any further changes that may have been made to
+	 * the underlying headers, e.g. via a previously obtained instance.
+	 */
+	public HttpHeaders getWrittenHeaders() {
+		return writtenHeaders;
+	}
+
 	@Override
 	public OutputStream getBody() throws IOException {
-		this.headersWritten = true;
+		writeHeaders();
 		return body;
 	}
 
 	public byte[] getBodyAsBytes() {
-		this.headersWritten = true;
+		writeHeaders();
 		return body.toByteArray();
 	}
 
@@ -54,4 +67,13 @@ public class MockHttpOutputMessage implements HttpOutputMessage {
 		byte[] bytes = getBodyAsBytes();
 		return new String(bytes, charset);
 	}
+
+	private void writeHeaders() {
+		if (this.headersWritten) {
+			return;
+		}
+		this.headersWritten = true;
+		this.writtenHeaders.putAll(this.headers);
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -33,6 +33,11 @@ import org.springframework.util.FileCopyUtils;
 
 import static org.junit.Assert.*;
 
+/**
+ * Unit tests for BufferedImageHttpMessageConverter.
+ * @author Arjen Poutsma
+ * @author Rossen Stoyanchev
+ */
 public class BufferedImageHttpMessageConverterTests {
 
 	private BufferedImageHttpMessageConverter converter;
@@ -73,7 +78,7 @@ public class BufferedImageHttpMessageConverterTests {
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
 		MediaType contentType = new MediaType("image", "png");
 		converter.write(body, contentType, outputMessage);
-		assertEquals("Invalid content type", contentType, outputMessage.getHeaders().getContentType());
+		assertEquals("Invalid content type", contentType, outputMessage.getWrittenHeaders().getContentType());
 		assertTrue("Invalid size", outputMessage.getBodyAsBytes().length > 0);
 		BufferedImage result = ImageIO.read(new ByteArrayInputStream(outputMessage.getBodyAsBytes()));
 		assertEquals("Invalid height", 500, result.getHeight());
@@ -88,7 +93,7 @@ public class BufferedImageHttpMessageConverterTests {
 		BufferedImage body = ImageIO.read(logo.getFile());
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
 		converter.write(body, new MediaType("*", "*"), outputMessage);
-		assertEquals("Invalid content type", contentType, outputMessage.getHeaders().getContentType());
+		assertEquals("Invalid content type", contentType, outputMessage.getWrittenHeaders().getContentType());
 		assertTrue("Invalid size", outputMessage.getBodyAsBytes().length > 0);
 		BufferedImage result = ImageIO.read(new ByteArrayInputStream(outputMessage.getBodyAsBytes()));
 		assertEquals("Invalid height", 500, result.getHeight());