Spring Boot - RabbitMQ - Changing message content type from octet-stream to json - spring

Question

I having issue getting from my Byte[] message received in RabbitMQ converted into some object based on a model.
I'm using Spring Boot.
In the application I have implemented RabbitListenerConfigurer:
#SpringBootApplication
class Application : RabbitListenerConfigurer {
...
override fun configureRabbitListeners(registrar: RabbitListenerEndpointRegistrar) {
registrar.messageHandlerMethodFactory = messageHandlerMethodFactory()
}
#Bean
fun messageHandlerMethodFactory(): MessageHandlerMethodFactory {
val messageHandlerMethodFactory = DefaultMessageHandlerMethodFactory()
messageHandlerMethodFactory.setMessageConverter(consumerJackson2MessageConverter())
return messageHandlerMethodFactory
}
#Bean
fun consumerJackson2MessageConverter(): MappingJackson2MessageConverter {
return MappingJackson2MessageConverter()
}
}
I then have a listener (the println is just for the time being for me to check) like:
#RabbitListener(queues = ["success.queue"])
fun receivedSuccessMessage(data: MyModel) {
println(data)
}
And the model itself looks like (again simplified just for testing):
#JsonIgnoreProperties(ignoreUnknown = true)
data class MyModel(
val input: Any,
val metadata: Any
)
Now whenever that queue gets a message the error i get is:
Caused by: org.springframework.messaging.converter.MessageConversionException: Cannot convert from [[B] to [com.models.MyModel] for GenericMessage [payload=byte[1429]
Also to add the message I'm receving into that success queue looks like this:
{"input":"somestuff", "metadata": "somestuff"}
And I also just noticed that the message type is coming in as content_type: application/octet-stream. This is out of my control as thats just what I am receiving from the service that puts the message in there:
Any ideas why this is - I assumed that RabbitListenerConfigurer implementation I have does the conversion for all messages from byte array into whatever model I specify.
Any help/ideas would be appreciated.
Thanks.
UPDATE
Ok I got this working, however I'm quite confused about something:
This is what I added in:
#Autowired
lateinit var connectionFactory : ConnectionFactory
#Bean
fun rabbitListenerContainerFactory(): SimpleRabbitListenerContainerFactory {
val factory = SimpleRabbitListenerContainerFactory()
factory.setConnectionFactory(connectionFactory)
factory.setAfterReceivePostProcessors(SomeBusiness())
return factory
}
And then the actual conversion like this:
class SomeBusiness : MessagePostProcessor {
#Throws(AmqpException::class)
override fun postProcessMessage(message: Message): Message {
println("WE WENT IN NOW")
println()
if (message.messageProperties.contentType == "application/octet-stream") {
message.messageProperties.contentType = "application/json"
}
return message
}
}
However the thing I don't understand is I already have my messageHandlerMethodFactory function which I assumed did all the work around listening to messages. Now that I have rabbitListenerContainerFactory is there any concern of anything conflicting. Or is it perfectly valid, namely I need rabbitListenerContainerFactory as it implements SimpleRabbitListenerContainerFactory which gives me access to the method setAfterReceivePostProcessors.
Again, any explanation would really be appreciated.
Thanks

Answer 1

As you are receiving content_type: application/octet-stream and this can't changed.
You could use Spring Interceptor Or Servlet Filter to convert the content type application/octet-stream to application/json.
Example using HandlerInterceptor for Spring Boot Hope this helps. Thanks

Answer 2

Please find the below source which is working for me,
public void convertByteArrayToObject(Message<?> message) {
Object request = message.getPayload();
Object result = null;
try {
byte[] byteArray = (byte[]) request;
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArray);
result = new ObjectInputStream(byteArrayInputStream).readObject();
} catch (ClassNotFoundException | IOException e) {
LOG.error(e.getMessage());
}
return result;
}

Answer 3

I had the same problem. Solution below helped me to solve it.
Solution:
Spring understand only "contentType", not "content_type". So, just set "contentType" property for your message, for example (in my case message producer was not spring app):
String json = ...;
TextMessage textMessage = session.createTextMessage(json);
textMessage.setStringProperty("contentType", "application/json");
Explanation:
Class MappingJackson2MessageConverter has method canConvertFrom(Message<?> message, #Nullable Class<?> targetClass). That method checks if headers contains supported mime types. And if to dive deeper, we will find that AbstractMessageConverter.getMimeType(MessageHeaders header) has contentTypeResolver, who gets appropriate property. Instance of that object located in CompositeMessageConverterFactory, it's DefaultContentResolver, which gets content type in method resolve(MessageHeaders headers):
Object contentType = headers.get(MessageHeaders.CONTENT_TYPE);
Where public static final String CONTENT_TYPE = "contentType";