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Editor to share with you how to achieve stateful stateful calculation in flink, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Import org.apache.flink.api.common.functions.RichFlatMapFunctionimport org.apache.flink.api.common.state.ValueStateimport org.apache.flink.util.Collectorimport org.apache.flink.configuration.Configurationimport org.apache.flink.api.common.state.ValueStateDescriptorimport org.apache.flink.streaming.api.scala.StreamExecutionEnvironment class CountWindowAverage extends RichFlatMapFunction [(Long, Double), (Long, Double)] {private var sum: ValueState [(Long, Double)] = _ override def flatMap (input: (Long, Double), out: Collector [(Long) Double)]): Unit = {/ / access the state valueval tmpCurrentSum = sum.value / / If it hasn't been used before, it will be null val currentSum = if (tmpCurrentSum! = null) {tmpCurrentSum} else {(0L, 0d)} / / update the count val newSum = (currentSum._1 + 1, currentSum._2 + input._2) / / update the state sum.update (newSum) / / if the count reaches 2 Emit the average and clear the state if (newSum._1 > = 2) {out.collect ((input._1, newSum._2 / newSum._1)) / / clear the state / / sum.clear ()}} override def open (parameters: Configuration): Unit = {sum = getRuntimeContext.getState (new ValueStateDescriptor [(Long, Double)] ("average", classOf [(Long) Double)}} import org.apache.flink.streaming.api.scala.StreamExecutionEnvironmentimport org.apache.flink.api.scala._object ECountWindowAverage {def main (args: Array [String]): Unit = {val env = StreamExecutionEnvironment.getExecutionEnvironment env.fromCollection (List ((1L, 3D), (1L, 5d), (1L, 7d), (1L, 4d), (1L, 4d), (1L KeyBy (_. _ 1) .flatMap (new CountWindowAverage ()) .print () / * .keyBy (_. _ 1) .flatMap (new CountWindowAverage ()) .print () * / the printed output will be (1line 4) and (1jue 5) env.execute ("ExampleManagedState")} above are all the contents of the article "how to implement stateful stateful calculation in flink" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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