1.flatmap核心包含两部操作：

1.将数据切分

2.拍扁

 

 

示例：

输出结果：
import org.apache.flink.api.scala.createTypeInformation
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment

object flatMapTest {
  def main(args: Array[String]): Unit = {

    //create env
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    //create ds
    val ds = env.fromElements("hadoop is good", "spark is fast", "flink is better")

    val flatMapedDs = ds.flatMap(_.split(" "))

    flatMapedDs.print()

    env.execute()


  }

}

输出结果：

 

2.自定义flatmap方法

 

核心操作：

1.继承FlatMapFunction类

2.重写flatMap方法

示例：

import org.apache.flink.api.common.functions.FlatMapFunction
import org.apache.flink.api.scala.createTypeInformation
import org.apache.flink.streaming.api.scala.StreamExecutionEnvironment
import org.apache.flink.util.Collector

object myFlatMapTest {

  //defined my flatMap func

  //judge the word length,bigger than special length then split,else do nothing
  class myFlatMap(maxWordLength:Int) extends FlatMapFunction[String, String]{
    override def flatMap(t: String, collector: Collector[String]): Unit = {

      if (t.length>maxWordLength){
        t.split(" ").foreach(collector.collect)
      }
    }
  }

  def main(args: Array[String]): Unit = {

    //create env
    val env = StreamExecutionEnvironment.getExecutionEnvironment

    //create ds
    val ds = env.fromElements("this is a good morning, long long long and long", "that day is friday")

//use my flatMap func

    val flatMapedDs = ds.flatMap(new myFlatMap(25))

    flatMapedDs.print()

    env.execute()
 

  }

}



输出结果：