Support String contentType headers in spring-messaging

After this change DefaultContentTypeResolver supports String-based
"contentType" header values in addition to MimeType-based.

Issue: SPR-11461

spring-messaging/src/main/java/org/springframework/messaging/converter/DefaultContentTypeResolver.java

@@ -21,8 +21,9 @@ import org.springframework.util.MimeType;
 
 /**
  * A default {@link ContentTypeResolver} that checks the
- * {@link MessageHeaders#CONTENT_TYPE} header or falls back to a default, if a default is
- * configured.
+ * {@link MessageHeaders#CONTENT_TYPE} header or falls back to a default value,
+ * The header value is expected to be a {@link org.springframework.util.MimeType}
+ * or a String that can be parsed into a {@code MimeType}.
  *
  * @author Rossen Stoyanchev
  * @since 4.0
@@ -33,15 +34,18 @@ public class DefaultContentTypeResolver implements ContentTypeResolver {
 
 
 	/**
-	 * Set the default MIME type to use, if the message headers don't have one.
-	 * By default this property is set to {@code null}.
+	 * Set the default MIME type to use when there is no
+	 * {@link MessageHeaders#CONTENT_TYPE} header present.
+	 * <p>
+	 * This property does not have a default value.
 	 */
 	public void setDefaultMimeType(MimeType defaultMimeType) {
 		this.defaultMimeType = defaultMimeType;
 	}
 
 	/**
-	 * Return the default MIME type to use.
+	 * Return the default MIME type to use if no
+	 * {@link MessageHeaders#CONTENT_TYPE} header is present.
 	 */
 	public MimeType getDefaultMimeType() {
 		return this.defaultMimeType;
@@ -49,15 +53,25 @@ public class DefaultContentTypeResolver implements ContentTypeResolver {
 
 	@Override
 	public MimeType resolve(MessageHeaders headers) {
-		MimeType mimeType = null;
-		if (headers != null) {
-			mimeType = headers.get(MessageHeaders.CONTENT_TYPE, MimeType.class);
+		if (headers == null || headers.get(MessageHeaders.CONTENT_TYPE) == null) {
+			return this.defaultMimeType;
+		}
+		Object value = headers.get(MessageHeaders.CONTENT_TYPE);
+		if (value instanceof MimeType) {
+			return (MimeType) value;
+		}
+		else if (value instanceof String) {
+			return MimeType.valueOf((String) value);
+		}
+		else {
+			throw new IllegalArgumentException(
+					"Unknown type for contentType header value: " + value.getClass());
 		}
-		return (mimeType != null) ? mimeType : this.defaultMimeType;
 	}
 
 	@Override
 	public String toString() {
 		return "DefaultContentTypeResolver[" + "defaultMimeType=" + this.defaultMimeType + "]";
 	}
+
 }

spring-messaging/src/test/java/org/springframework/messaging/converter/DefaultContentTypeResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -24,6 +24,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.converter.DefaultContentTypeResolver;
+import org.springframework.util.InvalidMimeTypeException;
 import org.springframework.util.MimeTypeUtils;
 
 import static org.junit.Assert.*;
@@ -52,6 +53,31 @@ public class DefaultContentTypeResolverTests {
 		assertEquals(MimeTypeUtils.APPLICATION_JSON, this.resolver.resolve(headers));
 	}
 
+	@Test
+	public void resolveStringContentType() {
+		Map<String, Object> map = new HashMap<String, Object>();
+		map.put(MessageHeaders.CONTENT_TYPE, MimeTypeUtils.APPLICATION_JSON_VALUE);
+		MessageHeaders headers = new MessageHeaders(map);
+
+		assertEquals(MimeTypeUtils.APPLICATION_JSON, this.resolver.resolve(headers));
+	}
+
+	@Test(expected = InvalidMimeTypeException.class)
+	public void resolveInvalidStringContentType() {
+		Map<String, Object> map = new HashMap<String, Object>();
+		map.put(MessageHeaders.CONTENT_TYPE, "invalidContentType");
+		MessageHeaders headers = new MessageHeaders(map);
+		this.resolver.resolve(headers);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void resolveUnknownHeaderType() {
+		Map<String, Object> map = new HashMap<String, Object>();
+		map.put(MessageHeaders.CONTENT_TYPE, new Integer(1));
+		MessageHeaders headers = new MessageHeaders(map);
+		this.resolver.resolve(headers);
+	}
+
 	@Test
 	public void resolveNoContentTypeHeader() {
 		MessageHeaders headers = new MessageHeaders(Collections.<String, Object>emptyMap());
@@ -60,7 +86,7 @@ public class DefaultContentTypeResolverTests {
 	}
 
 	@Test
-	public void resolveFromDefaultMimeType() {
+	public void resolveDefaultMimeType() {
 		this.resolver.setDefaultMimeType(MimeTypeUtils.APPLICATION_JSON);
 		MessageHeaders headers = new MessageHeaders(Collections.<String, Object>emptyMap());