akka.stream.stage

Class AbstractStage<In,Out,PushD extends Directive,PullD extends Directive,Ctx extends Context<Out>,LifeCtx extends LifecycleContext>

java.lang.Object

akka.stream.stage.AbstractStage<In,Out,PushD,PullD,Ctx,LifeCtx>

All Implemented Interfaces:

Stage<In,Out>

Direct Known Subclasses:

DetachedStage, PushPullStage

Deprecated.

Please use GraphStage instead. Since 2.4.2.

public abstract class AbstractStage<In,Out,PushD extends Directive,PullD extends Directive,Ctx extends Context<Out>,LifeCtx extends LifecycleContext>
extends java.lang.Object
implements Stage<In,Out>

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractStage.PushPullGraphStage<In,Out,Ext> Deprecated.
static class	AbstractStage.PushPullGraphStageWithMaterializedValue<In,Out,Ext,Mat> Deprecated.

Constructor Summary

Constructors

Constructor and Description
AbstractStage() Deprecated.

Method Summary

Modifier and Type	Method and Description
Supervision.Directive	decide(java.lang.Throwable t) Deprecated. If an exception is thrown from onPush(In, Ctx) this method is invoked to decide how to handle the exception.
boolean	isDetached() Deprecated. INTERNAL API
TerminationDirective	onDownstreamFinish(Ctx ctx) Deprecated. onDownstreamFinish is called when downstream has canceled.
abstract PullD	onPull(Ctx ctx) Deprecated. onPull is called when there is demand from downstream, i.e.
abstract PushD	onPush(In elem, Ctx ctx) Deprecated. onPush is called when an element from upstream is available and there is demand from downstream, i.e.
TerminationDirective	onUpstreamFailure(java.lang.Throwable cause, Ctx ctx) Deprecated. onUpstreamFailure is called when upstream has signaled that the stream is completed with failure.
TerminationDirective	onUpstreamFinish(Ctx ctx) Deprecated. onUpstreamFinish is called when upstream has signaled that the stream is successfully completed.
void	postStop() Deprecated. User overridable callback.
void	preStart(LifeCtx ctx) Deprecated. User overridable callback.
Stage<In,Out>	restart() Deprecated. Used to create a fresh instance of the stage after an error resulting in a Supervision.Restart directive.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractStage

public AbstractStage()

Deprecated.

Method Detail

isDetached

public boolean isDetached()

Deprecated.

INTERNAL API

Returns:

(undocumented)

preStart

public void preStart(LifeCtx ctx)
              throws java.lang.Exception

Deprecated.

User overridable callback.

It is called before any other method defined on the Stage. Empty default implementation.

Parameters:

ctx - (undocumented)

Throws:

java.lang.Exception

onPush

public abstract PushD onPush(In elem,
                             Ctx ctx)

Deprecated.

onPush is called when an element from upstream is available and there is demand from downstream, i.e. in onPush you are allowed to call Context.push(Out) to emit one element downstream, or you can absorb the element by calling Context.pull(). Note that you can only emit zero or one element downstream from onPull.

To emit more than one element you have to push the remaining elements from onPull(Ctx), one-by-one. onPush is not called again until onPull has requested more elements with Context.pull().

Parameters:

elem - (undocumented)

ctx - (undocumented)

Returns:

(undocumented)

onPull

public abstract PullD onPull(Ctx ctx)

Deprecated.

onPull is called when there is demand from downstream, i.e. you are allowed to push one element downstream with Context.push(Out), or request elements from upstreams with Context.pull()

Parameters:

ctx - (undocumented)

Returns:

(undocumented)

onUpstreamFinish

public TerminationDirective onUpstreamFinish(Ctx ctx)

Deprecated.

onUpstreamFinish is called when upstream has signaled that the stream is successfully completed. Here you cannot call Context.push(Out), because there might not be any demand from downstream. To emit additional elements before terminating you can use Context.absorbTermination() and push final elements from onPull(Ctx). The stage will then be in finishing state, which can be checked with Context.isFinishing().

By default the finish signal is immediately propagated with Context.finish().

*IMPORTANT NOTICE:* this signal is not back-pressured, it might arrive from upstream even though the last action by this stage was a &ldquo;push&rdquo;.

Parameters:

ctx - (undocumented)

Returns:

(undocumented)

onDownstreamFinish

public TerminationDirective onDownstreamFinish(Ctx ctx)

Deprecated.

onDownstreamFinish is called when downstream has canceled.

By default the cancel signal is immediately propagated with Context.finish().

Parameters:

ctx - (undocumented)

Returns:

(undocumented)

onUpstreamFailure

public TerminationDirective onUpstreamFailure(java.lang.Throwable cause,
                                              Ctx ctx)

Deprecated.

onUpstreamFailure is called when upstream has signaled that the stream is completed with failure. It is not called if onPull(Ctx) or onPush(In, Ctx) of the stage itself throws an exception.

Note that elements that were emitted by upstream before the failure happened might not have been received by this stage when onUpstreamFailure is called, i.e. failures are not backpressured and might be propagated as soon as possible.

Here you cannot call Context.push(Out), because there might not be any demand from downstream. To emit additional elements before terminating you can use Context.absorbTermination() and push final elements from onPull(Ctx). The stage will then be in finishing state, which can be checked with Context.isFinishing().

Parameters:

cause - (undocumented)

ctx - (undocumented)

Returns:

(undocumented)

postStop

public void postStop()
              throws java.lang.Exception

Deprecated.

User overridable callback.

Is called after the Stages final action is performed. // TODO need better wording here Empty default implementation.

Throws:

java.lang.Exception

decide

public Supervision.Directive decide(java.lang.Throwable t)

Deprecated.

If an exception is thrown from onPush(In, Ctx) this method is invoked to decide how to handle the exception. By default this method returns Supervision.Stop.

If an exception is thrown from onPull(Ctx) the stream will always be completed with failure, because it is not always possible to recover from that state. In concrete stages it is of course possible to use ordinary try-catch-recover inside onPull when it is know how to recover from such exceptions.

Parameters:

t - (undocumented)

Returns:

(undocumented)

restart

public Stage<In,Out> restart()

Deprecated.

Used to create a fresh instance of the stage after an error resulting in a Supervision.Restart directive. By default it will return the same instance untouched, so you must override it if there are any state that should be cleared before restarting, e.g. by returning a new instance.

Returns:

(undocumented)