一、自定义DataSource

​ 自定义DataSource有两大类：单线程的DataSource和多线程的DataSource

• 单线程：继承 SourceFunction

• 多线程：继承 ParallelSourceFunction，继承 RichParallelSourceFunction（可以有其他的很多操作）

  import org.apache.flink.configuration.Configuration
  import org.apache.flink.streaming.api.functions.source.{ParallelSourceFunction, RichParallelSourceFunction, SourceFunction}
  
  //1. 单线程
  class MyNoParallelSource1 extends SourceFunction[Long] {
  
    var count = 1L;
    var isRunning = true
  
    override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
      while(isRunning) {
        ctx.collect(count)
        count += 1
        Thread.sleep(1000)
      }
    }
  
    override def cancel(): Unit = {
      isRunning = false
    }
  }
  
  //2. 多线程
  class MyNoParallelSource2 extends ParallelSourceFunction[Long] {
  
    var count = 1L
    var isRunning = true
  
    override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
      while(isRunning) {
        ctx.collect(count)
        count += 1
        Thread.sleep(1000)
      }
    }
  
    override def cancel(): Unit = {
      isRunning = false
    }
  }
  
  /**3. 多线程使用RichFunction的方式
   * 提供了open和close方法，可以用于打开和释放资源
   */
  class MyNoParallelSource3 extends RichParallelSourceFunction[Long] {
  
    var count = 1
    var isRunning = true
  
    override def run(ctx: SourceFunction.SourceContext[Long]): Unit = {
      while (isRunning) {
        ctx.collect(count)
        count += 1
        Thread.sleep(1000)
      }
    }
  
    override def cancel(): Unit = {
      isRunning = false
    }
  
    override def open(parameters: Configuration): Unit = super.open(parameters)
  
    override def close(): Unit = super.close()
    
  }