Called when a message is received by the subscriber. The implementation must arrange for AckReplyConsumer#ack() or AckReplyConsumer#nack() to be called after processing the
message.
// This {@code MessageReceiver} passes all messages to a BlockingQueue. This method can// be called concurrently from multiple threads, so it is important that the queue be// thread-safe.//// This example is for illustration. Implementations may directly process messages instead of// sending them to queues.MessageReceiverreceiver=newMessageReceiver(){publicvoidreceiveMessage(finalPubsubMessagemessage,finalAckReplyConsumerconsumer){if(blockingQueue.offer(message)){consumer.ack();}else{consumer.nack();}}};