Scala Callback类代码示例

//设置package包名称以及导入依赖的类
package pl.touk.nussknacker.engine.kafka

import org.apache.kafka.clients.producer.{Callback, KafkaProducer, ProducerRecord, RecordMetadata}
import scala.concurrent.{Future, Promise}
import scala.util.{Failure, Success, Try}

trait EspSimpleKafkaProducer {
  val kafkaConfig: KafkaConfig

  def sendToKafkaWithNewProducer(topic: String, key: Array[Byte], value: Array[Byte]): Future[RecordMetadata] = {
    var producer: KafkaProducer[Array[Byte], Array[Byte]] = null
    try {
      producer = createProducer()
      sendToKafka(topic, key, value)(producer)
    } finally {
      if (producer != null) {
        producer.close()
      }
    }
  }

  //method with such signature already exists in "net.cakesolutions" %% "scala-kafka-client" % "0.9.0.0" but I struggled to add this dependency...
  def sendToKafka(topic: String, key: Array[Byte], value: Array[Byte])(producer: KafkaProducer[Array[Byte], Array[Byte]]): Future[RecordMetadata] = {
    val promise = Promise[RecordMetadata]()
    producer.send(new ProducerRecord(topic, key, value), producerCallback(promise))
    promise.future
  }

  def createProducer(): KafkaProducer[Array[Byte], Array[Byte]] = {
    new KafkaProducer[Array[Byte], Array[Byte]](KafkaEspUtils.toProducerProperties(kafkaConfig))
  }

  private def producerCallback(promise: Promise[RecordMetadata]): Callback =
    new Callback {
      override def onCompletion(metadata: RecordMetadata, exception: Exception): Unit = {
        val result = if (exception == null) Success(metadata) else Failure(exception)
        promise.complete(result)
      }
    }
} 

//设置package包名称以及导入依赖的类
package articlestreamer.kafka

import org.apache.kafka.clients.producer.{Callback, RecordMetadata}

class RecordCallback extends Callback {

  override def onCompletion(metadata: RecordMetadata, ex: Exception) = {
    if (ex != null) {
      handleException(ex)
    } else {
      println(s"Successfully sent message : $metadata")
    }
  }
  
  def handleException(exception: Exception): Unit = {
    Console.err.println(s"Error while attempting to send message : $exception")
  }
} 

//设置package包名称以及导入依赖的类
package de.choffmeister.microserviceutils.kafka

import akka.NotUsed
import akka.kafka.ProducerMessage.Result
import akka.kafka.{ProducerMessage, ProducerSettings}
import org.apache.kafka.clients.producer.{Callback, ProducerRecord, RecordMetadata}

import scala.concurrent.{Future, Promise}

class SimpleProducer[K, V](producerSettings: ProducerSettings[K, V]) {
  private val producer = producerSettings.createKafkaProducer()

  def send(record: ProducerRecord[K, V]): Future[Result[K, V, NotUsed]] = {
    val promise = Promise[Result[K, V, NotUsed]]
    val callback = new Callback {
      override def onCompletion(metadata: RecordMetadata, exception: Exception): Unit = {
        Option(exception) match {
          case Some(err) => promise.failure(err)
          case None => promise.success(Result(metadata, ProducerMessage.Message(record, NotUsed)))
        }
      }
    }

    producer.send(record, callback)
    promise.future
  }
} 

//设置package包名称以及导入依赖的类
package bidding.client.console

import org.apache.kafka.clients.producer.{Callback, KafkaProducer, ProducerRecord, RecordMetadata}

class Bidder(producer: KafkaProducer[String, String], itemId: String, startPrice: BigDecimal) {
  private var lastPrice: BigDecimal = startPrice

  private val callback = new Callback {
    override def onCompletion(metadata: RecordMetadata, exception: Exception): Unit = {
      println("published: " + metadata.toString)
    }
  }

  def bid(): Unit = {
    val producerRecord = new ProducerRecord("my-replicated-topic", itemId, lastPrice.toString())
    producer.send(producerRecord, callback)
    lastPrice += BigDecimal(scala.util.Random.nextDouble * 2)
  }
} 

//设置package包名称以及导入依赖的类
package articlestreamer.shared.kafka

import com.typesafe.scalalogging.LazyLogging
import org.apache.kafka.clients.producer.{Callback, RecordMetadata}

class RecordCallback extends Callback with LazyLogging {

  override def onCompletion(metadata: RecordMetadata, ex: Exception) = {
    if (ex != null) {
      handleException(ex)
    } else {
      logger.info(s"Successfully sent message : $metadata")
    }
  }
  
  private def handleException(exception: Exception): Unit = {
    logger.error("Error while attempting to send message", exception)
  }
}