我有一个从SupervisorActor中创建的Actor,这个Actor负责将它获取的消息推送到流中。这是演员:
class KafkaPublisher[T <: KafkaMessage: ClassTag] extends Actor {
implicit val system = context.system
val log = Logging(system, this.getClass.getName)
override final def receive = {
case ProducerStreamActivated(_, stream: SourceQueueWithComplete[T]) =>
log.info(s"Activated stream for Kafka Producer with ActorName >> ${self.path.name} << ActorPath >> ${self.path} <<")
context.become(active(stream))
case other =>
log.warning("KafkaPublisher got some unknown message while producing: " + other)
}
def active(stream: SourceQueueWithComplete[T]): Receive = {
case msg: T =>
log.info(s"Got Message >> $msg << Pushing it to stream $stream")
stream.offer(msg)
case other =>
log.warning("KafkaPublisher got the unknown message while producing: " + other)
}
}
object KafkaPublisher {
def props[T <: KafkaMessage: ClassTag] =
Props(new KafkaPublisher[T])
}
可以看出,此Actor适用于通用消息类型,因为SupervisorActor负责创建此通用Actor的具体实例。
trait Event
object Event {
case class ProducerStreamActivated[T <: KafkaMessage](kafkaTopic: String, stream: SourceQueueWithComplete[T]) extends Event
}
trait KafkaMessage
object KafkaMessage {
case class DefaultMessage(message: String, timestamp: DateTime) extends KafkaMessage {
def this() = this("DEFAULT-EMPTY-MESSAGE", DateTime.now(DateTimeZone.UTC))
}
case class DefaultMessageBundle(messages: Seq[DefaultMessage], timeStamp: DateTime) extends KafkaMessage {
def this() = this(Seq.empty, DateTime.now(DateTimeZone.UTC))
}
}
显然,我收到以下错误:
Error:(17, 45) pattern type is incompatible with expected type;
found : akka.stream.scaladsl.SourceQueueWithComplete[T]
required: akka.stream.scaladsl.SourceQueueWithComplete[com.eon.pm.messages.KafkaMessage]
Note: T <: com.my.project.messages.KafkaMessage, but trait SourceQueueWithComplete is invariant in type T.
You may wish to define T as +T instead. (SLS 4.5)
case ProducerStreamActivated(_, stream: SourceQueueWithComplete[T]) =>
SourceQueueWithComplete不是Covariant。我该如何缓解这种情况?有什么建议吗?
答案 0 :(得分:1)
像:
class KafkaPublisher extends Actor {
implicit val system = context.system
val log = Logging(system, this.getClass.getName)
override final def receive = {
case ProducerStreamActivated(_, stream) =>
log.info(s"Activated stream for Kafka Producer with ActorName >> ${self.path.name} << ActorPath >> ${self.path} <<")
context.become(active(stream))
case other =>
log.warning("KafkaPublisher got some unknown message while producing: " + other)
}
def active(stream: SourceQueueWithComplete[KafkaMessage]): Receive = {
case msg: DefaultMessage =>
log.info(s"Got Message >> $msg << Pushing it to stream $stream")
stream.offer(msg)
case msg: DefaultMessageBundle =>
log.info(s"Got Message >> $msg << Pushing it to stream $stream")
stream.offer(msg)
case other =>
log.warning("KafkaPublisher got the unknown message while producing: " + other)
}
}
object KafkaPublisher {
def props = Props(new KafkaPublisher)
}
trait Event
object Event {
case class ProducerStreamActivated(kafkaTopic: String, stream: SourceQueueWithComplete[KafkaMessage]) extends Event
}
trait KafkaMessage
object KafkaMessage {
case class DefaultMessage(message: String, timestamp: DateTime) extends KafkaMessage {
def this() = this("DEFAULT-EMPTY-MESSAGE", DateTime.now(DateTimeZone.UTC))
}
case class DefaultMessageBundle(messages: Seq[DefaultMessage], timeStamp: DateTime) extends KafkaMessage {
def this() = this(Seq.empty, DateTime.now(DateTimeZone.UTC))
}
}