Using SqsListener with SNS and SQS

Question

I'm using spring-cloud-aws 's SqsListener to receive AWS SNS HTTP Notifications in JSON Format from AWS's Simple Queue Service (SQS).

This is the code for the listener:

@SqsListener(value = "my-queue", deletionPolicy = SqsMessageDeletionPolicy.ON_SUCCESS)
public void handle(final MyObject obj) throws Exception {
// ...
}

The documentation linked above is only about sending and reading plain serialized objects to the Queue and I thought that receiving SNS messages is expected to work out of the box. But I end up receiving conversion errors:

10:45:51.480 [simpleMessageListenerContainer-2] ERROR oscamlSimpleMessageListenerContainer - Exception encountered while processing message. org.springframework.messaging.MessagingException: An exception occurred while invoking the handler method; nested exception is org.springframework.messaging.converter.MessageConversionException: No converter found to convert to class com.myproject.model.MyObject, message=GenericMessage

I also tried creating a wrapper object that looks like the expected SNS Json Format linked above, but I keep getting the same exception. The only type that works is a String in the signature. Shouldn't the SNS be converted automatically?

Answer 1

Yes it should. And it does actually.

In order to have the correct HandlerMethodArgumentResolver invoked (in this case NotificationMessageArgumentResolver ) on deserialization, which in turn invokes the correct converter NotificationRequestConverter you simply need to add the annotation org.springframework.cloud.aws.messaging.config.annotation.NotificationMessage to your method signature. Eg

@SqsListener(value = "my-queue", deletionPolicy = SqsMessageDeletionPolicy.ON_SUCCESS)
public void handle(final @NotificationMessage MyObject obj) throws Exception {
// ...
}

This way the Message part of your SNS gets extracted and converted to MyObject .

Answer 2

This works without the @NotificationMessage as well. This way you don't need to send the "Type" and "Message" part, that is required to work with this annotation.

First create a class with the needed attributes.

public class SqsMessage {

   private String myTask;

   public SqsMessage() {
   }

   public SqsMessage(@JsonProperty("MyTask") String myTask ) {
       this.myTask = myTask ;
   }

   //Getter + Setter 
}

Next set up the Listener

@SqsListener(value = {"MyQueue"}, deletionPolicy = SqsMessageDeletionPolicy.ON_SUCCESS)
public void receiveMessage(SqsMessage payload, @Headers Map<String, Object> header) {
   logger.info("Got message with task: " + payload.getTask() 
    + " with custom attribute " + header.get("CustomAttribute").toString());
}

Now you can send a JSON like

{"MyTask":"My task"}

The @JsonProperty("MyTask") annoation in the POJO's constructor can be optional, depending on your spring version and if your attribute has the same name as in the Json string. It's not necessary for example, if your attribute is called task and your Json string is {"task":"My task"} .