Package org.elasticsearch.action

Class StepListener<Response>

java.lang.Object

org.elasticsearch.action.NotifyOnceListener<Response>

org.elasticsearch.action.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);
  }
 

Nested Class Summary

Nested classes/interfaces inherited from interface org.elasticsearch.action.ActionListener

ActionListener.Delegating<Response,DelegateResponse>, ActionListener.DelegatingActionListener<T>, ActionListener.DelegatingFailureActionListener<T,R>, ActionListener.MappedActionListener<Response,MappedResponse>, ActionListener.RunAfterActionListener<T>, ActionListener.RunBeforeActionListener<T>

Constructor Summary

Constructors

Constructor	Description
StepListener()

Method Summary

Modifier and Type	Method	Description
void	addListener(ActionListener<Response> listener)	Registers the given listener to be notified with the result of this step.
Future<Response>	asFuture()	Returns the future associated with the given step listener
protected void	innerOnFailure(Exception e)
protected void	innerOnResponse(Response response)
Response	result()	Gets the result of this step.
<OtherResponse, OuterResponse> StepListener<OuterResponse>	thenCombine(StepListener<OtherResponse> other, BiFunction<Response,OtherResponse,OuterResponse> fn)	Combines this listener with another one, waiting for both to successfully complete and combining their results.
void	whenComplete(org.elasticsearch.core.CheckedConsumer<Response,Exception> onResponse, Consumer<Exception> onFailure)	Registers the given actions which are called when this step is completed.

Methods inherited from class org.elasticsearch.action.NotifyOnceListener

onFailure, onResponse

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.elasticsearch.action.ActionListener

delegateFailure, delegateResponse, map

Constructor Details

StepListener

public StepListener()

Method Details

innerOnResponse

protected void innerOnResponse(Response response)

Specified by:

innerOnResponse in class NotifyOnceListener<Response>

innerOnFailure

protected void innerOnFailure(Exception e)

Specified by:

innerOnFailure in class NotifyOnceListener<Response>

whenComplete

public void whenComplete(org.elasticsearch.core.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

thenCombine

public <OtherResponse,
OuterResponse>
StepListener<OuterResponse> thenCombine(StepListener<OtherResponse> other,
 BiFunction<Response,OtherResponse,OuterResponse> fn)

Combines this listener with another one, waiting for both to successfully complete and combining their results.

Parameters:

other - the other step listener to combine with

fn - the function that combines the results

Returns:

the combined listener

asFuture

public Future<Response> asFuture()

Returns the future associated with the given step listener

result

public Response result()

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

addListener

public void addListener(ActionListener<Response> listener)

Registers the given listener to be notified with the result of this step.