Kafka流中的自定义时间戳提取器

Question

我正在尝试使用Kafka流来处理Kafka主题中的一些数据。数据来自Kafka0.11.0编写的Kafka主题，该主题没有嵌入时间戳。在网上读了一些书之后，我明白了我可以通过在自定义类中扩展TimestampExtractor类并将其传递到StreamsConfig中来解决这个问题。

我是这样做的-

class MyEventTimestampExtractor extends TimestampExtractor {
  override def extract(record: ConsumerRecord[AnyRef, AnyRef], prev: Long) = {
    record.value() match {
        case w: String => 1000L
        case _ => throw new RuntimeException(s"Called for $record")
    }
  }
}

我基于github上的这段代码

但是，当我运行sbt时，我会遇到这个错误

[error] /home/someuser/app/blahblah/src/main/scala/main.scala:34: class MyEventTimestampExtractor needs to be abstract, since method extract in trait TimestampExtractor of type (x$1: org.apache.kafka.clients.consumer.ConsumerRecord[Object,Object], x$2: Long)Long is not defined
[error] (Note that Long does not match Long)
[error] class MyEventTimestampExtractor extends TimestampExtractor {
[error]       ^
[error] /home/someuser/app/blahblah/src/main/scala/main.scala:35: method extract overrides nothing.
[error] Note: the super classes of class MyEventTimestampExtractor contain the following, non final members named extract:
[error] def extract(x$1: org.apache.kafka.clients.consumer.ConsumerRecord[Object,Object],x$2: Long): Long
[error]   override def extract(record: ConsumerRecord[AnyRef, AnyRef], prev: Long): Long = {
[error]                ^
[error] two errors found
[error] (compile:compileIncremental) Compilation failed

我的身材。这是sbt文件吗--

name := "kafka streams experiment"
version := "1.0"
scalaVersion := "2.12.4"

libraryDependencies ++= Seq(
  "org.apache.kafka" % "kafka-streams" % "1.0.0"
)

我真的不明白这个错误。特别是周围的部分，请注意Long与Long不匹配。我可能做错了什么？谢谢




Answer 1

尝试（观察prev函数参数的类型：

  override def extract(record: ConsumerRecord[AnyRef, AnyRef], prev: java.lang.Long) = {

Answer 2

你需要java。因为这个API是用Java定义的，而您使用的是Scala Long