Package org.elasticsearch.action

Class StepListener<Response>

  • All Implemented Interfaces:
    ActionListener<Response>
    public final class StepListener<Response>
extends NotifyOnceListener<Response>
    A StepListener provides a simple way to write a flow consisting of multiple asynchronous steps without having nested callbacks. For example: 
    
  void asyncFlowMethod(... ActionListener<R> flowListener) {
    StepListener<R1> step1 = new StepListener<>();
    asyncStep1(..., step1);

    StepListener<R2> step2 = new StepListener<>();
    step1.whenComplete(r1 -> {
      asyncStep2(r1, ..., step2);
    }, flowListener::onFailure);

    step2.whenComplete(r2 -> {
      R1 r1 = step1.result();
      R r = combine(r1, r2);
     flowListener.onResponse(r);
    }, flowListener::onFailure);
  }

    • Constructor Detail

      • StepListener

        public StepListener()

    • Method Detail

      • whenComplete

        public void whenComplete​(CheckedConsumer<Response,​Exception> onResponse,
                         Consumer<Exception> onFailure)
        Registers the given actions which are called when this step is completed. If this step is completed successfully, the onResponse is called with the result; otherwise the onFailure is called with the failure.
        Parameters:
        onResponse - is called when this step is completed successfully
        onFailure - is called when this step is completed with a failure

      • result

        public Response result()
        Gets the result of this step. This method will throw IllegalStateException if this step is not completed yet.