Default interceptor for legacy contentType

Fixes #1057

Enable consumers to convert from originalContentType to contentType in the case of
legacy producers sending messages with originalContentType header.
By default, this conversion will not happen and only be acitvated by setting
`spring.cloud.stream.bindings.input.legacyContentTypeHeaderEnabled` to true.

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/LegacyContentTypeTests.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2015-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.stream.config;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.stream.annotation.EnableBinding;
+import org.springframework.cloud.stream.binder.BinderHeaders;
+import org.springframework.cloud.stream.messaging.Sink;
+import org.springframework.context.annotation.PropertySource;
+import org.springframework.integration.support.MessageBuilder;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHandler;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.messaging.MessagingException;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Soby Chacko
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringBootTest(classes = { LegacyContentTypeTests.LegacyTestSink.class})
+public class LegacyContentTypeTests {
+
+	@Autowired
+	private Sink testSink;
+
+	@Test
+	public void testOriginalContentTypeIsRetrievedForLegacyContentHeaderType() throws Exception {
+		final CountDownLatch latch = new CountDownLatch(1);
+		MessageHandler messageHandler = new MessageHandler() {
+			@Override
+			public void handleMessage(Message<?> message) throws MessagingException {
+				assertThat(message.getPayload()).isInstanceOf(byte[].class);
+				assertThat(message.getPayload()).isEqualTo("{\"message\":\"Hi\"}".getBytes());
+				assertThat(message.getHeaders().get(MessageHeaders.CONTENT_TYPE)).isEqualTo("application/json");
+				latch.countDown();
+			}
+		};
+		testSink.input().subscribe(messageHandler);
+		testSink.input().send(MessageBuilder.withPayload("{\"message\":\"Hi\"}".getBytes()).setHeader(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE, "application/json").build());
+		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
+		testSink.input().unsubscribe(messageHandler);
+	}
+
+	@EnableBinding(Sink.class)
+	@EnableAutoConfiguration
+	@PropertySource("classpath:/org/springframework/cloud/stream/config/channel/legacy-sink-channel-configurers.properties")
+	public static class LegacyTestSink {
+
+	}
+}

spring-cloud-stream-integration-tests/src/test/resources/org/springframework/cloud/stream/config/channel/legacy-sink-channel-configurers.properties

@@ -0,0 +1,4 @@
+spring.cloud.stream.bindings.input.destination=configure1
+spring.cloud.stream.bindings.input.legacyContentTypeHeaderEnabled=true
+spring.cloud.stream.bindings.input.contentType=application/x-spring-tuple
+

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binding/MessageConverterConfigurer.java

@@ -60,6 +60,7 @@ import org.springframework.util.StringUtils;
  * @author Marius Bogoevici
  * @author Maxim Kirilov
  * @author Gary Russell
+ * @author Soby Chacko
  */
 public class MessageConverterConfigurer
 		implements MessageChannelConfigurer, BeanFactoryAware, InitializingBean {
@@ -120,6 +121,9 @@ public class MessageConverterConfigurer
 					getPartitionKeyExtractorStrategy(producerProperties),
 					getPartitionSelectorStrategy(producerProperties)));
 		}
+		if (input && bindingProperties.isLegacyContentTypeHeaderEnabled()) {
+			messageChannel.addInterceptor(new LegacyContentTypeHeaderInterceptor());
+		}
 		// TODO: Set all interceptors in the correct order for input/output channels
 		if (StringUtils.hasText(contentType)) {
 			messageChannel.addInterceptor(
@@ -298,4 +302,19 @@ public class MessageConverterConfigurer
 		}
 	}
 
+	private final class LegacyContentTypeHeaderInterceptor extends ChannelInterceptorAdapter {
+
+		@Override
+		public Message<?> preSend(Message<?> message, MessageChannel channel) {
+			Object originalContentType = message.getHeaders().get(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE);
+			if (originalContentType != null) {
+				return MessageConverterConfigurer.this.messageBuilderFactory
+						.fromMessage(message)
+						.setHeader(MessageHeaders.CONTENT_TYPE, originalContentType).build();
+			}
+			return message;
+		}
+
+	}
+
 }

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/config/BindingProperties.java

@@ -31,6 +31,7 @@ import org.springframework.validation.annotation.Validated;
  * @author Marius Bogoevici
  * @author Ilayaperumal Gopinathan
  * @author Gary Russell
+ * @author Soby Chacko
  */
 @JsonInclude(Include.NON_DEFAULT)
 @Validated
@@ -57,6 +58,8 @@ public class BindingProperties {
 
 	private String contentType = MimeTypeUtils.APPLICATION_JSON_VALUE;
 
+	private boolean legacyContentTypeHeaderEnabled = false;
+
 	private String binder;
 
 	private ConsumerProperties consumer;
@@ -87,6 +90,14 @@ public class BindingProperties {
 		this.contentType = contentType;
 	}
 
+	public boolean isLegacyContentTypeHeaderEnabled() {
+		return legacyContentTypeHeaderEnabled;
+	}
+
+	public void setLegacyContentTypeHeaderEnabled(boolean legacyContentTypeHeaderEnabled) {
+		this.legacyContentTypeHeaderEnabled = legacyContentTypeHeaderEnabled;
+	}
+
 	public String getBinder() {
 		return binder;
 	}

spring-cloud-stream/src/test/java/org/springframework/cloud/stream/binding/MessageConverterConfigurerTests.java

@@ -20,6 +20,7 @@ import java.util.Collections;
 
 import org.junit.Test;
 
+import org.springframework.cloud.stream.binder.BinderHeaders;
 import org.springframework.cloud.stream.config.BindingProperties;
 import org.springframework.cloud.stream.config.BindingServiceProperties;
 import org.springframework.cloud.stream.converter.CompositeMessageConverterFactory;
@@ -97,6 +98,27 @@ public class MessageConverterConfigurerTests {
 		}
 	}
 
+	@Test
+	public void testConfigureInputChannelWithLegacyContentType() {
+		BindingServiceProperties props = new BindingServiceProperties();
+		BindingProperties bindingProps = new BindingProperties();
+		bindingProps.setContentType("foo/bar");
+		bindingProps.setLegacyContentTypeHeaderEnabled(true);
+		props.setBindings(Collections.singletonMap("foo", bindingProps));
+		CompositeMessageConverterFactory converterFactory = new CompositeMessageConverterFactory(
+				Collections.<MessageConverter>emptyList(), null);
+		MessageConverterConfigurer configurer = new MessageConverterConfigurer(props, converterFactory);
+		QueueChannel in = new QueueChannel();
+		configurer.configureInputChannel(in, "foo");
+		Foo foo = new Foo();
+		in.send(new GenericMessage<>(foo,
+				Collections.singletonMap(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE, "application/json")));
+		Message<?> received = in.receive(0);
+		assertThat(received).isNotNull();
+		assertThat(received.getPayload()).isEqualTo(foo);
+		assertThat(received.getHeaders().get(MessageHeaders.CONTENT_TYPE)).isEqualTo("application/json");
+	}
+
 	public static class Foo {
 
 		private String bar = "bar";