Fix issue in BufferedImageHttpMessageConverter

This change ensures BufferedImageHttpMessageConverter writes when
"*/*" is requested.

Issue: SPR-7763

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

@@ -132,7 +132,7 @@ public class BufferedImageHttpMessageConverter implements HttpMessageConverter<B
 	}
 
 	private boolean isWritable(MediaType mediaType) {
-		if (mediaType == null) {
+		if (mediaType == null || MediaType.ALL.equals(mediaType)) {
 			return true;
 		}
 		Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByMIMEType(mediaType.toString());
@@ -191,7 +191,7 @@ public class BufferedImageHttpMessageConverter implements HttpMessageConverter<B
 	public void write(BufferedImage image, MediaType contentType, HttpOutputMessage outputMessage)
 			throws IOException, HttpMessageNotWritableException {
 
-		if (contentType == null) {
+		if (contentType == null || contentType.isWildcardType() || contentType.isWildcardSubtype()) {
 			contentType = getDefaultContentType();
 		}
 		Assert.notNull(contentType,

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

@@ -51,6 +51,7 @@ public class BufferedImageHttpMessageConverterTests {
 	public void canWrite() {
 		assertTrue("Image not supported", converter.canWrite(BufferedImage.class, null));
 		assertTrue("Image not supported", converter.canWrite(BufferedImage.class, new MediaType("image", "png")));
+		assertTrue("Image not supported", converter.canWrite(BufferedImage.class, new MediaType("*", "*")));
 	}
 
 	@Test
@@ -85,7 +86,7 @@ public class BufferedImageHttpMessageConverterTests {
 		converter.setDefaultContentType(contentType);
 		BufferedImage body = ImageIO.read(logo.getFile());
 		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
-		converter.write(body, contentType, outputMessage);
+		converter.write(body, new MediaType("*", "*"), outputMessage);
 		assertEquals("Invalid content type", contentType, outputMessage.getHeaders().getContentType());
 		assertTrue("Invalid size", outputMessage.getBodyAsBytes().length > 0);
 		BufferedImage result = ImageIO.read(new ByteArrayInputStream(outputMessage.getBodyAsBytes()));