AbstractJackson2MessageConv.: assume supported CT

For the JSON and XML converters, assume the content type is supported
if missing or default.
Add option to revert to previous behavior.

spring-amqp/src/main/java/org/springframework/amqp/support/converter/AbstractJackson2MessageConverter.java

@@ -85,6 +85,8 @@ public abstract class AbstractJackson2MessageConverter extends AbstractMessageCo
 
 	private boolean standardCharset;
 
+	private boolean assumeSupportedContentType = true;
+
 	/**
 	 * Construct with the provided {@link ObjectMapper} instance.
 	 * @param objectMapper the {@link ObjectMapper} to use.
@@ -218,6 +220,19 @@ public void setUseProjectionForInterfaces(boolean useProjectionForInterfaces) {
 		}
 	}
 
+	/**
+	 * By default the supported content type is assumed when there is no contentType
+	 * property or it is set to the default ('application/octet-stream'). Set to 'false'
+	 * to revert to the previous behavior of returning an unconverted 'byte[]' when this
+	 * condition exists.
+	 * @param assumeSupportedContentType set false to not assume the content type is
+	 * supported.
+	 * @since 2.2
+	 */
+	public void setAssumeSupportedContentType(boolean assumeSupportedContentType) {
+		this.assumeSupportedContentType = assumeSupportedContentType;
+	}
+
 	@Override
 	public Object fromMessage(Message message) throws MessageConversionException {
 		return fromMessage(message, null);
@@ -233,7 +248,8 @@ public Object fromMessage(Message message, @Nullable Object conversionHint) thro
 		MessageProperties properties = message.getMessageProperties();
 		if (properties != null) {
 			String contentType = properties.getContentType();
-			if (contentType != null && contentType.contains(this.supportedContentType.getSubtype())) {
+			if ((this.assumeSupportedContentType && (contentType == null || contentType.equals(MessageProperties.DEFAULT_CONTENT_TYPE)))
+					|| (contentType != null && contentType.contains(this.supportedContentType.getSubtype()))) {
 				String encoding = properties.getContentEncoding();
 				if (encoding == null) {
 					encoding = getDefaultCharset();

spring-amqp/src/test/java/org/springframework/amqp/support/converter/Jackson2JsonMessageConverterTests.java

@@ -189,8 +189,9 @@ public void testNoJsonContentType() {
 		byte[] bytes = "{\"name\" : \"foo\" }".getBytes();
 		MessageProperties messageProperties = new MessageProperties();
 		Message message = new Message(bytes, messageProperties);
-		Object foo = jsonConverterWithDefaultType.fromMessage(message);
-		assertThat(new String((byte[]) foo)).isEqualTo(new String(bytes));
+		this.jsonConverterWithDefaultType.setAssumeSupportedContentType(false);
+		Object foo = this.jsonConverterWithDefaultType.fromMessage(message);
+		assertThat(foo).isEqualTo(bytes);
 	}
 
 	@Test
@@ -280,6 +281,27 @@ public void testProjection() {
 		assertThat(((Sample) fromMessage).getName()).isEqualTo("SomeName");
 	}
 
+	@Test
+	public void testMissingContentType() {
+		byte[] bytes = "{\"name\" : \"foo\" }".getBytes();
+		MessageProperties messageProperties = new MessageProperties();
+		Message message = new Message(bytes, messageProperties);
+		Jackson2JsonMessageConverter j2Converter = new Jackson2JsonMessageConverter();
+		DefaultClassMapper classMapper = new DefaultClassMapper();
+		classMapper.setDefaultType(Foo.class);
+		j2Converter.setClassMapper(classMapper);
+		Object foo = j2Converter.fromMessage(message);
+		assertThat(foo).isInstanceOf(Foo.class);
+
+		messageProperties.setContentType(null);
+		foo = j2Converter.fromMessage(message);
+		assertThat(foo).isInstanceOf(Foo.class);
+
+		j2Converter.setAssumeSupportedContentType(false);
+		foo = j2Converter.fromMessage(message);
+		assertThat(foo).isSameAs(bytes);
+	}
+
 	public static class Foo {
 
 		private String name = "foo";

spring-amqp/src/test/java/org/springframework/amqp/support/converter/Jackson2XmlMessageConverterTests.java

@@ -187,8 +187,9 @@ public void testNoJsonContentType() {
 		byte[] bytes = "<root><name>foo</name><root/>".getBytes();
 		MessageProperties messageProperties = new MessageProperties();
 		Message message = new Message(bytes, messageProperties);
-		Object foo = xmlConverterWithDefaultType.fromMessage(message);
-		assertThat(new String(bytes)).isEqualTo(new String((byte[]) foo));
+		this.xmlConverterWithDefaultType.setAssumeSupportedContentType(false);
+		Object foo = this.xmlConverterWithDefaultType.fromMessage(message);
+		assertThat(foo).isEqualTo(bytes);
 	}
 
 	@Test

src/reference/asciidoc/amqp.adoc

@@ -3398,7 +3398,9 @@ for convenience.)
 If you inject a custom type mapper, you should set the property on the mapper instead.
 
 NOTE: When converting from the `Message`, an incoming `MessageProperties.getContentType()` must be JSON-compliant (`contentType.contains("json")` is used to check).
-Otherwise, a `WARN` log message `Could not convert incoming message with content-type [...]`, is emitted and `message.getBody()` is returned as is -- as a `byte[]`.
+Starting with version 2.2, `application/json` is assumed if there is no `contentType` property, or it has the default value `application/octet-stream`.
+To revert to the previous behavior (return an unconverted `byte[]`), set the converter's `assumeSupportedContentType` property to `false`.
+If the content type is not supported, a `WARN` log message `Could not convert incoming message with content-type [...]`, is emitted and `message.getBody()` is returned as is -- as a `byte[]`.
 So, to meet the `Jackson2JsonMessageConverter` requirements on the consumer side, the producer must add the `contentType` message property -- for example, as `application/json` or `text/x-json` or by using the `Jackson2JsonMessageConverter`, which sets the header automatically.
 The following listing shows a number of converter calls:
 
@@ -3521,6 +3523,7 @@ The following example shows how to configure a `MarshallingMessageConverter`:
 ----
 ====
 
+[[jackson2xml]]
 ===== `Jackson2XmlMessageConverter`
 
 This class was introduced in version 2.1 and can be used to convert messages from and to XML.
@@ -3547,6 +3550,9 @@ The following example configures a `Jackson2JsonMessageConverter`:
 ----
 See <<json-message-converter>> for more information.
 
+NOTE: Starting with version 2.2, `application/xml` is assumed if there is no `contentType` property, or it has the default value `application/octet-stream`.
+To revert to the previous behavior (return an unconverted `byte[]`), set the converter's `assumeSupportedContentType` property to `false`.
+
 ===== `ContentTypeDelegatingMessageConverter`
 
 This class was introduced in version 1.4.2 and allows delegation to a specific `MessageConverter` based on the content type property in the `MessageProperties`.

src/reference/asciidoc/whats-new.adoc

@@ -33,6 +33,12 @@ See <<choose-container>> for more information.
 Spring Data Projection interfaces are now supported by the `Jackson2JsonMessageConverter`.
 See <<data-projection>> for more information.
 
+The `Jackson2JsonMessageConverter` now assumes the content is JSON if there is no `contentType` property, or it is the default (`application/octet-string`).
+See <<Jackson2JsonMessageConverter-from-message>> for more information.
+
+Similarly. the `Jackson2XmlMessageConverter` now assumes the content is XML if there is no `contentType` property, or it is the default (`application/octet-string`).
+See <<jackson2xml>> for more information.
+
 ===== AMQP Logging Appenders Changes
 
 The Log4J and Logback `AmqpAppender` s now support a `verifyHostname` SSL option.