Scala WindowFunction不编译
我一直在使用ApacheFlink编写一个原型应用程序。在这个过程中,我选择使用org.apache.flink.streaming.api.functions.windowing.WindowFunction作为特定用例。然而,在编写apply函数的主体时,我遇到了这个错误。下面的代码不是来自我正在编写的应用程序-我的数据类型不同-它来自Flink文档站点中提供的示例代码:Scala WindowFunction不编译,scala,apache-flink,flink-streaming,Scala,Apache Flink,Flink Streaming,我一直在使用ApacheFlink编写一个原型应用程序。在这个过程中,我选择使用org.apache.flink.streaming.api.functions.windowing.WindowFunction作为特定用例。然而,在编写apply函数的主体时,我遇到了这个错误。下面的代码不是来自我正在编写的应用程序-我的数据类型不同-它来自Flink文档站点中提供的示例代码: import scala.collection.Iterable import scala.collection.Map
import scala.collection.Iterable
import scala.collection.Map
import org.apache.flink.streaming.api.functions.windowing.WindowFunction
import org.apache.flink.streaming.api.windowing.windows.{TimeWindow}
import org.apache.flink.util.Collector
import scala.collection.JavaConversions._
class MyWindowFunction extends WindowFunction[(String, Long), String, String, TimeWindow] {
def apply(key: String, window: TimeWindow, input: Iterable[(String, Long)], out: Collector[String]): Unit = {
var count = 0L
for (in <- input) {
count = count + 1
}
out.collect(s"Window $window count: $count")
}
}
我已检查应用中参数的顺序;他们似乎是对的
由于某种原因,我未能找到错误的确切来源。有人能帮我找到解决办法吗?我找到了这个错误的原因 我不清楚的是,Apache Flink的API需要一个java.lang.Iterable,而不是它的Scala等价物:
class MyWindowFunction extends
WindowFunction[(String, Long), String, String, TimeWindow] {
override
def apply(
key: String,
w: TimeWindow,
iterable: Iterable[(String, Long)], // from java.lang.Iterable
collector: Collector[String]): Unit = {
// ....
}
}
因此,我必须适当地导入:
import java.lang.Iterable // From Java
import java.util.Map // From Java
import org.apache.flink.streaming.api.functions.windowing.WindowFunction
import org.apache.flink.streaming.api.windowing.windows.TimeWindow
import org.apache.flink.util.Collector
import scala.collection.JavaConversions._ // Implicit conversions
class MyWindowFunction
extends WindowFunction[(String, Long), String, String, TimeWindow] {
override
def apply(
key: String,
w: TimeWindow,
iterable: Iterable[(String, Long)],
collector: Collector[String]): Unit = {
// ....
}
}
一切都很好
import java.lang.Iterable // From Java
import java.util.Map // From Java
import org.apache.flink.streaming.api.functions.windowing.WindowFunction
import org.apache.flink.streaming.api.windowing.windows.TimeWindow
import org.apache.flink.util.Collector
import scala.collection.JavaConversions._ // Implicit conversions
class MyWindowFunction
extends WindowFunction[(String, Long), String, String, TimeWindow] {
override
def apply(
key: String,
w: TimeWindow,
iterable: Iterable[(String, Long)],
collector: Collector[String]): Unit = {
// ....
}
}