AMQP-141: create base class for converters

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

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2002-2010 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.amqp.support.converter;
+
+import java.util.UUID;
+
+import org.springframework.amqp.core.Message;
+import org.springframework.amqp.core.MessageProperties;
+
+/**
+ * Convenient base class for {@link MessageConverter} implementations.
+ * @author Dave Syer
+ * 
+ */
+public abstract class AbstractMessageConverter implements MessageConverter {
+
+	private boolean createMessageIds = false;
+
+	/**
+	 * Flag to indicate that new messages should have unique identifiers added to their properties before sending.
+	 * Default false.
+	 * @param createMessageIds the flag value to set
+	 */
+	public void setCreateMessageIds(boolean createMessageIds) {
+		this.createMessageIds = createMessageIds;
+	}
+
+	/**
+	 * Flag to indicate that new messages should have unique identifiers added to their properties before sending.
+	 * @return the flag value
+	 */
+	protected boolean isCreateMessageIds() {
+		return createMessageIds;
+	}
+
+	public final Message toMessage(Object object, MessageProperties messageProperties)
+			throws MessageConversionException {
+		if (messageProperties==null) {
+			messageProperties = new MessageProperties();
+		}
+		Message message = createMessage(object, messageProperties);
+		messageProperties = message.getMessageProperties();
+		if (this.createMessageIds && messageProperties.getMessageId()==null) {
+			messageProperties.setMessageId(UUID.randomUUID().toString());
+		}
+		return message;
+	}
+
+	/**
+	 * Crate a message from the payload object and message properties provided. The message id will be added to the
+	 * properties if necessary later.
+	 * 
+	 * @param object the payload
+	 * @param messageProperties the message properties (headers)
+	 * @return a message
+	 */
+	abstract protected Message createMessage(Object object, MessageProperties messageProperties);
+
+	abstract public Object fromMessage(Message message) throws MessageConversionException;
+
+}

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

@@ -33,9 +33,7 @@ import org.springframework.amqp.core.MessageProperties;
  * @author James Carr
  * @author Dave Syer
  */
-public class JsonMessageConverter implements MessageConverter {
-
-	// TODO create composite MessageConverter with key/value pairs of content-type/converter. introduce base class
+public class JsonMessageConverter extends AbstractMessageConverter {
 
 	private static Log log = LogFactory.getLog(JsonMessageConverter.class);
 
@@ -125,7 +123,7 @@ public class JsonMessageConverter implements MessageConverter {
 		return jsonObjectMapper.readValue(contentAsString, targetClass);
 	}
 
-	public Message toMessage(Object objectToConvert, MessageProperties messageProperties)
+	protected Message createMessage(Object objectToConvert, MessageProperties messageProperties)
 			throws MessageConversionException {
 		byte[] bytes = null;
 		try {

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

@@ -17,7 +17,6 @@
 package org.springframework.amqp.support.converter;
 
 import java.io.ByteArrayInputStream;
-
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 
@@ -42,7 +41,7 @@ import org.springframework.util.Assert;
  * @see org.springframework.amqp.rabbit.core.RabbitTemplate#convertAndSend
  * @see org.springframework.amqp.rabbit.core.RabbitTemplate#receiveAndConvert
  */
-public class MarshallingMessageConverter implements MessageConverter, InitializingBean {
+public class MarshallingMessageConverter extends AbstractMessageConverter implements InitializingBean {
 
 	private Marshaller marshaller;
 
@@ -118,7 +117,7 @@ public class MarshallingMessageConverter implements MessageConverter, Initializi
 	/**
 	 * Marshals the given object to a {@link Message}.
 	 */
-	public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
+	protected Message createMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
 		try {
 			ByteArrayOutputStream bos = new ByteArrayOutputStream();
 			StreamResult streamResult = new StreamResult(bos);

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

@@ -33,7 +33,7 @@ import org.springframework.core.serializer.Serializer;
  * 
  * @author Dave Syer
  */
-public class SerializerMessageConverter implements MessageConverter {
+public class SerializerMessageConverter extends AbstractMessageConverter {
 
 	public static final String DEFAULT_CHARSET = "UTF-8";
 
@@ -117,7 +117,7 @@ public class SerializerMessageConverter implements MessageConverter {
 	/**
 	 * Creates an AMQP Message from the provided Object.
 	 */
-	public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
+	protected Message createMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
 		byte[] bytes = null;
 		if (object instanceof String) {
 			try {

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

@@ -22,7 +22,6 @@ import java.io.InputStream;
 import java.io.ObjectInputStream;
 import java.io.Serializable;
 import java.io.UnsupportedEncodingException;
-import java.util.UUID;
 
 import org.springframework.amqp.core.Message;
 import org.springframework.amqp.core.MessageProperties;
@@ -40,7 +39,7 @@ import org.springframework.util.ClassUtils;
  * @author Mark Fisher
  * @author Oleg Zhurakousky
  */
-public class SimpleMessageConverter implements MessageConverter, BeanClassLoaderAware {
+public class SimpleMessageConverter extends AbstractMessageConverter implements BeanClassLoaderAware {
 
 	public static final String DEFAULT_CHARSET = "UTF-8";
 
@@ -50,21 +49,10 @@ public class SimpleMessageConverter implements MessageConverter, BeanClassLoader
 
 	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();
 
-	private boolean createMessageIds = false;
-	
 	public void setBeanClassLoader(ClassLoader beanClassLoader) {
 		this.beanClassLoader = beanClassLoader;
 	}
 
-	/**
-	 * Flag to indicate that new messages should have unique identifiers added to their properties before sending.
-	 * Default false.
-	 * @param createMessageIds the flag value to set
-	 */
-	public void setCreateMessageIds(boolean createMessageIds) {
-		this.createMessageIds = createMessageIds;
-	}
-
 	/**
 	 * Set the codebase URL to download classes from if not found locally. Can consists of multiple URLs, separated by
 	 * spaces.
@@ -129,7 +117,7 @@ public class SimpleMessageConverter implements MessageConverter, BeanClassLoader
 	/**
 	 * Creates an AMQP Message from the provided Object.
 	 */
-	public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
+	protected Message createMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
 		byte[] bytes = null;		
 		if (object instanceof byte[]) {
 			bytes = (byte[]) object;
@@ -158,9 +146,6 @@ public class SimpleMessageConverter implements MessageConverter, BeanClassLoader
 		if (bytes != null) {
 			messageProperties.setContentLength(bytes.length);
 		}
-		if (this.createMessageIds && messageProperties.getMessageId()==null) {
-			messageProperties.setMessageId(UUID.randomUUID().toString());
-		}
 		return new Message(bytes, messageProperties);
 	}
 

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

@@ -17,6 +17,8 @@
 package org.springframework.amqp.support.converter;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -43,6 +45,21 @@ public class SimpleMessageConverterTests {
 		assertEquals("test", new String((byte[]) result, "UTF-8"));
 	}
 
+	@Test
+	public void noMessageIdByDefault() throws Exception {
+		SimpleMessageConverter converter = new SimpleMessageConverter();
+		Message message = converter.toMessage("foo", null);
+		assertNull(message.getMessageProperties().getMessageId());
+	}
+
+	@Test
+	public void optionalMessageId() throws Exception {
+		SimpleMessageConverter converter = new SimpleMessageConverter();
+		converter.setCreateMessageIds(true);
+		Message message = converter.toMessage("foo", null);
+		assertNotNull(message.getMessageProperties().getMessageId());
+	}
+
 	@Test
 	public void messageToString() {
 		SimpleMessageConverter converter = new SimpleMessageConverter();