java.lang.Object
- org.apache.pekko.stream.stage.GraphStageLogic

Direct Known Subclasses:

GraphStageLogicWithLogging, KillSwitches.KillableGraphStageLogic, TimerGraphStageLogic
```
public abstract class GraphStageLogic
extends java.lang.Object
```
Represents the processing logic behind a GraphStage. Roughly speaking, a subclass of GraphStageLogic is a collection of the following parts: * A set of InHandler and OutHandler instances and their assignments to the Inlets and Outlets of the enclosing GraphStage * Possible mutable state, accessible from the InHandler and OutHandler callbacks, but not from anywhere else (as such access would not be thread-safe) * The lifecycle hooks preStart() and postStop() * Methods for performing stream processing actions, like pulling or pushing elements
The operator logic is completed once all its input and output ports have been closed. This can be changed by setting setKeepGoing to true.
The postStop lifecycle hook on the logic itself is called once all ports are closed. This is the only tear down callback that is guaranteed to happen, if the actor system or the materializer is terminated the handlers may never see any callbacks to onUpstreamFailure, onUpstreamFinish or onDownstreamFinish. Therefore operator resource cleanup should always be done in postStop.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`GraphStageLogic.ConditionalTerminateInput`	Input handler that terminates the state upon receiving completion if the given condition holds at that time.
`static class`	`GraphStageLogic.ConditionalTerminateOutput`	Output handler that terminates the state upon receiving completion if the given condition holds at that time.
`static class`	`GraphStageLogic.EagerTerminateInput$`	Input handler that terminates the operator upon receiving completion.
`static class`	`GraphStageLogic.EagerTerminateOutput$`	Output handler that terminates the operator upon cancellation.
`static class`	`GraphStageLogic.IgnoreTerminateInput$`	Input handler that does not terminate the operator upon receiving completion.
`static class`	`GraphStageLogic.IgnoreTerminateOutput$`	Output handler that does not terminate the operator upon cancellation.
`static class`	`GraphStageLogic.StageActor`	Minimal actor to work with other actors and watch them in a synchronous ways
`static class`	`GraphStageLogic.StageActorRef$`
`static class`	`GraphStageLogic.StageActorRefNotInitializedException`
`static class`	`GraphStageLogic.StageActorRefNotInitializedException$`
`class`	`GraphStageLogic.SubSinkInlet<T>`	INTERNAL API
`class`	`GraphStageLogic.SubSourceOutlet<T>`	INTERNAL API
`static class`	`GraphStageLogic.TotallyIgnorantInput$`	Input handler that does not terminate the operator upon receiving completion nor failure.

Constructor Summary

Constructors
Constructor Description

GraphStageLogic(Shape shape)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`abortEmitting(Outlet<?> out)`	Abort outstanding (suspended) emissions for the given outlet, if there are any.
`protected void`	`abortReading(Inlet<?> in)`	Abort outstanding (suspended) reading for the given inlet, if there is any.
`protected void`	`afterPostStop()`	INTERNAL API
`protected void`	`beforePreStart()`	INTERNAL API
`protected <T> void`	`cancel(Inlet<T> in)`	Requests to stop receiving events from a given input port.
`protected <T> void`	`cancel(Inlet<T> in, java.lang.Throwable cause)`	Requests to stop receiving events from a given input port.
`void`	`cancelStage(java.lang.Throwable cause)`	Automatically invokes `<T>cancel(org.apache.pekko.stream.Inlet<T>)` or `<T>complete(org.apache.pekko.stream.Outlet<T>)` on all the input or output ports that have been called, then marks the stage as stopped.
`protected <T> void`	`complete(Outlet<T> out)`	Signals that there will be no more elements emitted on the given port.
`void`	`completeStage()`	Automatically invokes `<T>cancel(org.apache.pekko.stream.Inlet<T>)` or `<T>complete(org.apache.pekko.stream.Outlet<T>)` on all the input or output ports that have been called, then marks the operator as stopped.
`protected InHandler`	`conditionalTerminateInput(scala.Function0<java.lang.Object> predicate)`	Input handler that terminates the state upon receiving completion if the given condition holds at that time.
`protected OutHandler`	`conditionalTerminateOutput(scala.Function0<java.lang.Object> predicate)`	Output handler that terminates the state upon receiving completion if the given condition holds at that time.
`protected <T> AsyncCallback<T>`	`createAsyncCallback(Procedure<T> handler)`	Java API: Obtain a callback object that can be used asynchronously to re-enter the current `GraphStage` with an asynchronous notification.
`protected InHandler`	`eagerTerminateInput()`	Input handler that terminates the operator upon receiving completion.
`protected OutHandler`	`eagerTerminateOutput()`	Output handler that terminates the operator upon cancellation.
`protected <T> void`	`emit(Outlet<T> out, T elem)`	Emit an element through the given outlet, suspending execution if necessary.
`protected <T> void`	`emit(Outlet<T> out, T elem, Effect andThen)`
`protected <T> void`	`emit(Outlet<T> out, T elem, scala.Function0<scala.runtime.BoxedUnit> andThen)`	Emit an element through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
`protected <T> void`	`emitMultiple(Outlet<T> out, java.util.Iterator<T> elems)`	Java API
`protected <T> void`	`emitMultiple(Outlet<T> out, java.util.Iterator<T> elems, Effect andThen)`	Java API
`protected <T> void`	`emitMultiple(Outlet<T> out, scala.collection.immutable.Iterable<T> elems)`	Emit a sequence of elements through the given outlet, suspending execution if necessary.
`protected <T> void`	`emitMultiple(Outlet<T> out, scala.collection.immutable.Iterable<T> elems, scala.Function0<scala.runtime.BoxedUnit> andThen)`	Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
`protected <T> void`	`emitMultiple(Outlet<T> out, scala.collection.Iterator<T> elems)`	Emit a sequence of elements through the given outlet, suspending execution if necessary.
`protected <T> void`	`emitMultiple(Outlet<T> out, scala.collection.Iterator<T> elems, scala.Function0<scala.runtime.BoxedUnit> andThen)`	Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary.
`protected <T> void`	`fail(Outlet<T> out, java.lang.Throwable ex)`	Signals failure through the given port.
`void`	`failStage(java.lang.Throwable ex)`	Automatically invokes `<T>cancel(org.apache.pekko.stream.Inlet<T>)` or `<T>fail(org.apache.pekko.stream.Outlet<T>,java.lang.Throwable)` on all the input or output ports that have been called, then marks the operator as stopped.
`<T> AsyncCallback<T>`	`getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit> handler)`	Obtain a callback object that can be used asynchronously to re-enter the current `GraphStage` with an asynchronous notification.
`protected GraphStageLogic.StageActor`	`getEagerStageActor(Materializer eagerMaterializer, scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive)`	INTERNAL API
`protected InHandler`	`getHandler(Inlet<?> in)`	Retrieves the current callback for the events on the given `Inlet`
`protected OutHandler`	`getHandler(Outlet<?> out)`	Retrieves the current callback for the events on the given `Outlet`
`protected GraphStageLogic.StageActor`	`getStageActor(scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive)`	Initialize a `StageActorRef` which can be used to interact with from the outside world "as-if" an `Actor`.
`protected <T> T`	`grab(Inlet<T> in)`	Once the callback `InHandler.onPush` for an input port has been invoked, the element that has been pushed can be retrieved via this method.
`protected <T> boolean`	`hasBeenPulled(Inlet<T> in)`	Indicates whether there is already a pending pull for the given input port.
`protected InHandler`	`ignoreTerminateInput()`	Input handler that does not terminate the operator upon receiving completion.
`protected OutHandler`	`ignoreTerminateOutput()`	Output handler that does not terminate the operator upon cancellation.
`int`	`inCount()`
`protected <T> boolean`	`isAvailable(Inlet<T> in)`	Indicates whether there is an element waiting at the given input port.
`<T> boolean`	`isAvailable(Outlet<T> out)`	Return true if the given output port is ready to be pushed.
`protected <T> boolean`	`isClosed(Inlet<T> in)`	Indicates whether the port has been closed.
`protected <T> boolean`	`isClosed(Outlet<T> out)`	Indicates whether the port has been closed.
`protected Materializer`	`materializer()`	The `pekko.stream.Materializer` that has set this GraphStage in motion.
`int`	`outCount()`
`protected <Out,In extends Out> void`	`passAlong(Inlet<In> from, Outlet<Out> to, boolean doFinish, boolean doFail, boolean doPull)`	Install a handler on the given inlet that emits received elements on the given outlet before pulling for more data.
`protected <Out,In extends Out> boolean`	`passAlong$default$3()`
`protected <Out,In extends Out> boolean`	`passAlong$default$4()`
`protected <Out,In extends Out> boolean`	`passAlong$default$5()`
`void`	`postStop()`	Invoked after processing of external events stopped because the operator is about to stop or fail.
`void`	`preStart()`	Invoked before any external events are processed, at the startup of the operator.
`protected <T> void`	`pull(Inlet<T> in)`	Requests an element on the given port.
`protected <T> void`	`push(Outlet<T> out, T elem)`	Emits an element through the given output port.
`protected <T> void`	`read(Inlet<T> in, Procedure<T> andThen, Effect onClose)`	Java API: Read an element from the given inlet and continue with the given function, suspending execution if necessary.
`protected <T> void`	`read(Inlet<T> in, scala.Function1<T,scala.runtime.BoxedUnit> andThen, scala.Function0<scala.runtime.BoxedUnit> onClose)`	Read an element from the given inlet and continue with the given function, suspending execution if necessary.
`protected <T> void`	`readN(Inlet<T> in, int n, Procedure<java.util.List<T>> andThen, Procedure<java.util.List<T>> onClose)`	Java API: Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary.
`protected <T> void`	`readN(Inlet<T> in, int n, scala.Function1<scala.collection.immutable.Seq<T>,scala.runtime.BoxedUnit> andThen, scala.Function1<scala.collection.immutable.Seq<T>,scala.runtime.BoxedUnit> onClose)`	Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary.
`protected void`	`setHandler(Inlet<?> in, InHandler handler)`	Assigns callbacks for the events for an `Inlet`
`protected void`	`setHandler(Outlet<?> out, OutHandler handler)`	Assigns callbacks for the events for an `Outlet`
`protected void`	`setHandlers(Inlet<?> in, Outlet<?> out, InHandler handler)`	Assign callbacks for linear operator for both `Inlet` and `Outlet`
`protected void`	`setKeepGoing(boolean enabled)`	Controls whether this operator shall shut down when all its ports are closed, which is the default.
`GraphStageLogic.StageActor`	`stageActor()`
`protected java.lang.String`	`stageActorName()`	Override and return a name to be given to the StageActor of this operator.
`protected Materializer`	`subFusingMaterializer()`	An `pekko.stream.Materializer` that may run fusable parts of the graphs that it materializes within the same actor as the current GraphStage (if fusing is available).
`java.lang.String`	`toString()`
`protected InHandler`	`totallyIgnorantInput()`	Input handler that does not terminate the operator upon receiving completion nor failure.
`protected <T> void`	`tryPull(Inlet<T> in)`	Requests an element on the given port unless the port is already closed.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - GraphStageLogic
```
public GraphStageLogic(Shape shape)
```
- Method Detail
  - inCount
```
public int inCount()
```
  - outCount
```
public int outCount()
```
  - materializer
```
protected Materializer materializer()
```
    The pekko.stream.Materializer that has set this GraphStage in motion.
    Can not be used from a GraphStage constructor. Access to materializer is provided by the pekko.stream.scaladsl.Source.fromMaterializer, pekko.stream.scaladsl.Flow.fromMaterializer and pekko.stream.scaladsl.Sink.fromMaterializer and their corresponding Java API factories.
  - subFusingMaterializer
```
protected Materializer subFusingMaterializer()
```
    An pekko.stream.Materializer that may run fusable parts of the graphs that it materializes within the same actor as the current GraphStage (if fusing is available). This materializer must not be shared outside of the GraphStage.
  - eagerTerminateInput
```
protected final InHandler eagerTerminateInput()
```
    Input handler that terminates the operator upon receiving completion. The operator fails upon receiving a failure.
  - ignoreTerminateInput
```
protected final InHandler ignoreTerminateInput()
```
    Input handler that does not terminate the operator upon receiving completion. The operator fails upon receiving a failure.
  - conditionalTerminateInput
```
protected final InHandler conditionalTerminateInput(scala.Function0<java.lang.Object> predicate)
```
    Input handler that terminates the state upon receiving completion if the given condition holds at that time. The operator fails upon receiving a failure.
  - totallyIgnorantInput
```
protected final InHandler totallyIgnorantInput()
```
    Input handler that does not terminate the operator upon receiving completion nor failure.
  - eagerTerminateOutput
```
protected final OutHandler eagerTerminateOutput()
```
    Output handler that terminates the operator upon cancellation.
  - ignoreTerminateOutput
```
protected final OutHandler ignoreTerminateOutput()
```
    Output handler that does not terminate the operator upon cancellation.
  - conditionalTerminateOutput
```
protected final OutHandler conditionalTerminateOutput(scala.Function0<java.lang.Object> predicate)
```
    Output handler that terminates the state upon receiving completion if the given condition holds at that time. The operator fails upon receiving a failure.
  - setHandler
```
protected final void setHandler(Inlet<?> in,
                                InHandler handler)
```
    Assigns callbacks for the events for an Inlet
  - setHandlers
```
protected final void setHandlers(Inlet<?> in,
                                 Outlet<?> out,
                                 InHandler handler)
```
    Assign callbacks for linear operator for both Inlet and Outlet
  - getHandler
```
protected final InHandler getHandler(Inlet<?> in)
```
    Retrieves the current callback for the events on the given Inlet
  - setHandler
```
protected final void setHandler(Outlet<?> out,
                                OutHandler handler)
```
    Assigns callbacks for the events for an Outlet
  - getHandler
```
protected final OutHandler getHandler(Outlet<?> out)
```
    Retrieves the current callback for the events on the given Outlet
  - pull
```
protected final <T> void pull(Inlet<T> in)
```
    Requests an element on the given port. Calling this method twice before an element arrived will fail. There can only be one outstanding request at any given time. The method <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) can be used query whether pull is allowed to be called or not. This method will also fail if the port is already closed.
  - tryPull
```
protected final <T> void tryPull(Inlet<T> in)
```
    Requests an element on the given port unless the port is already closed. Calling this method twice before an element arrived will fail. There can only be one outstanding request at any given time. The method <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) can be used query whether pull is allowed to be called or not.
  - cancel
```
protected final <T> void cancel(Inlet<T> in)
```
    Requests to stop receiving events from a given input port. Cancelling clears any ungrabbed elements from the port.
    If cancellation is due to an error, use cancel(in, cause) instead to propagate that cause upstream. This overload is a shortcut for cancel(in, SubscriptionWithCancelException.NoMoreElementsNeeded)
  - cancel
```
protected final <T> void cancel(Inlet<T> in,
                                java.lang.Throwable cause)
```
    Requests to stop receiving events from a given input port. Cancelling clears any ungrabbed elements from the port.
  - grab
```
protected final <T> T grab(Inlet<T> in)
```
    Once the callback InHandler.onPush for an input port has been invoked, the element that has been pushed can be retrieved via this method. After <T>grab(org.apache.pekko.stream.Inlet<T>) has been called the port is considered to be empty, and further calls to <T>grab(org.apache.pekko.stream.Inlet<T>) will fail until the port is pulled again and a new element is pushed as a response.
    The method <T>isAvailable(org.apache.pekko.stream.Inlet<T>) can be used to query if the port has an element that can be grabbed or not.
  - hasBeenPulled
```
protected final <T> boolean hasBeenPulled(Inlet<T> in)
```
    Indicates whether there is already a pending pull for the given input port. If this method returns true then <T>isAvailable(org.apache.pekko.stream.Inlet<T>) must return false for that same port.
  - isAvailable
```
protected final <T> boolean isAvailable(Inlet<T> in)
```
    Indicates whether there is an element waiting at the given input port. <T>grab(org.apache.pekko.stream.Inlet<T>) can be used to retrieve the element. After calling <T>grab(org.apache.pekko.stream.Inlet<T>) this method will return false.
    If this method returns true then <T>hasBeenPulled(org.apache.pekko.stream.Inlet<T>) will return false for that same port.
  - isClosed
```
protected final <T> boolean isClosed(Inlet<T> in)
```
    Indicates whether the port has been closed. A closed port cannot be pulled.
  - push
```
protected final <T> void push(Outlet<T> out,
                              T elem)
```
    Emits an element through the given output port. Calling this method twice before a <T>pull(org.apache.pekko.stream.Inlet<T>) has been arrived will fail. There can be only one outstanding push request at any given time. The method <T>isAvailable(org.apache.pekko.stream.Inlet<T>) can be used to check if the port is ready to be pushed or not.
  - setKeepGoing
```
protected final void setKeepGoing(boolean enabled)
```
    Controls whether this operator shall shut down when all its ports are closed, which is the default. In order to have it keep going past that point this method needs to be called with a true argument before all ports are closed, and afterwards it will not be closed until this method is called with a false argument or the operator is terminated via completeStage() or failStage().
  - complete
```
protected final <T> void complete(Outlet<T> out)
```
    Signals that there will be no more elements emitted on the given port.
  - fail
```
protected final <T> void fail(Outlet<T> out,
                              java.lang.Throwable ex)
```
    Signals failure through the given port.
  - completeStage
```
public final void completeStage()
```
    Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>complete(org.apache.pekko.stream.Outlet<T>) on all the input or output ports that have been called, then marks the operator as stopped.
  - cancelStage
```
public final void cancelStage(java.lang.Throwable cause)
```
    Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>complete(org.apache.pekko.stream.Outlet<T>) on all the input or output ports that have been called, then marks the stage as stopped.
  - failStage
```
public final void failStage(java.lang.Throwable ex)
```
    Automatically invokes <T>cancel(org.apache.pekko.stream.Inlet<T>) or <T>fail(org.apache.pekko.stream.Outlet<T>,java.lang.Throwable) on all the input or output ports that have been called, then marks the operator as stopped.
  - isAvailable
```
public final <T> boolean isAvailable(Outlet<T> out)
```
    Return true if the given output port is ready to be pushed.
  - isClosed
```
protected final <T> boolean isClosed(Outlet<T> out)
```
    Indicates whether the port has been closed. A closed port cannot be pushed.
  - readN
```
protected final <T> void readN(Inlet<T> in,
                               int n,
                               scala.Function1<scala.collection.immutable.Seq<T>,scala.runtime.BoxedUnit> andThen,
                               scala.Function1<scala.collection.immutable.Seq<T>,scala.runtime.BoxedUnit> onClose)
```
    Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the last onPush() signal.
    If upstream closes before N elements have been read, the onClose function is invoked with the elements which were read.
  - readN
```
protected final <T> void readN(Inlet<T> in,
                               int n,
                               Procedure<java.util.List<T>> andThen,
                               Procedure<java.util.List<T>> onClose)
```
    Java API: Read a number of elements from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the last onPush() signal (before invoking the andThen function).
  - read
```
protected final <T> void read(Inlet<T> in,
                              scala.Function1<T,scala.runtime.BoxedUnit> andThen,
                              scala.Function0<scala.runtime.BoxedUnit> onClose)
```
    Read an element from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the onPush() signal (before invoking the andThen function).
  - read
```
protected final <T> void read(Inlet<T> in,
                              Procedure<T> andThen,
                              Effect onClose)
```
    Java API: Read an element from the given inlet and continue with the given function, suspending execution if necessary. This action replaces the InHandler for the given inlet if suspension is needed and reinstalls the current handler upon receiving the onPush() signal (before invoking the andThen function).
  - abortReading
```
protected final void abortReading(Inlet<?> in)
```
    Abort outstanding (suspended) reading for the given inlet, if there is any. This will reinstall the replaced handler that was in effect before the read call.
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.immutable.Iterable<T> elems,
                                      scala.Function0<scala.runtime.BoxedUnit> andThen)
```
    Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.immutable.Iterable<T> elems)
```
    Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      java.util.Iterator<T> elems)
```
    Java API
    Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the AbstractOutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      java.util.Iterator<T> elems,
                                      Effect andThen)
```
    Java API
    Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the AbstractOutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.Iterator<T> elems,
                                      scala.Function0<scala.runtime.BoxedUnit> andThen)
```
    Emit a sequence of elements through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).
  - emitMultiple
```
protected final <T> void emitMultiple(Outlet<T> out,
                                      scala.collection.Iterator<T> elems)
```
    Emit a sequence of elements through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.
  - emit
```
protected final <T> void emit(Outlet<T> out,
                              T elem,
                              scala.Function0<scala.runtime.BoxedUnit> andThen)
```
    Emit an element through the given outlet and continue with the given thunk afterwards, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal (before invoking the andThen function).
  - emit
```
protected final <T> void emit(Outlet<T> out,
                              T elem)
```
    Emit an element through the given outlet, suspending execution if necessary. This action replaces the OutHandler for the given outlet if suspension is needed and reinstalls the current handler upon receiving an onPull() signal.
  - emit
```
protected final <T> void emit(Outlet<T> out,
                              T elem,
                              Effect andThen)
```
  - abortEmitting
```
protected final void abortEmitting(Outlet<?> out)
```
    Abort outstanding (suspended) emissions for the given outlet, if there are any. This will reinstall the replaced handler that was in effect before the emit call.
  - passAlong
```
protected final <Out,In extends Out> void passAlong(Inlet<In> from,
                                                          Outlet<Out> to,
                                                          boolean doFinish,
                                                          boolean doFail,
                                                          boolean doPull)
```
    Install a handler on the given inlet that emits received elements on the given outlet before pulling for more data. doFinish and doFail control whether completion or failure of the given inlet shall lead to operator termination or not. doPull instructs to perform one initial pull on the from port.
  - passAlong$default$3
```
protected final <Out,In extends Out> boolean passAlong$default$3()
```
  - passAlong$default$4
```
protected final <Out,In extends Out> boolean passAlong$default$4()
```
  - passAlong$default$5
```
protected final <Out,In extends Out> boolean passAlong$default$5()
```
  - getAsyncCallback
```
public final <T> AsyncCallback<T> getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit> handler)
```
    Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification. The invoke method of the returned AsyncCallback is safe to be called from other threads. It will in the background thread-safely delegate to the passed callback function. I.e. invoke will be called by other thread and the passed handler will be invoked eventually in a thread-safe way by the execution environment.
    In case stream is not yet materialized AsyncCallback will buffer events until stream is available.
    AsyncCallback.invokeWithFeedback has an internal promise that will be failed if event cannot be processed due to stream completion.
    To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.
    This object can be cached and reused within the same GraphStageLogic.
  - createAsyncCallback
```
protected final <T> AsyncCallback<T> createAsyncCallback(Procedure<T> handler)
```
    Java API: Obtain a callback object that can be used asynchronously to re-enter the current GraphStage with an asynchronous notification. The invoke method of the returned AsyncCallback is safe to be called from other threads. It will in the background thread-safely delegate to the passed callback function. I.e. invoke will be called by other thread and the passed handler will be invoked eventually in a thread-safe way by the execution environment.
    AsyncCallback.invokeWithFeedback has an internal promise that will be failed if event cannot be processed due to stream completion.
    This object can be cached and reused within the same GraphStageLogic.
  - stageActor
```
public final GraphStageLogic.StageActor stageActor()
```
  - getStageActor
```
protected final GraphStageLogic.StageActor getStageActor(scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive)
```
    Initialize a StageActorRef which can be used to interact with from the outside world "as-if" an Actor. The messages are looped through the <T>getAsyncCallback(scala.Function1<T,scala.runtime.BoxedUnit>) mechanism of GraphStage so they are safe to modify internal state of this operator.
    This method must (the earliest) be called after the GraphStageLogic constructor has finished running, for example from the preStart() callback the graph operator logic provides.
    Created StageActorRef to get messages and watch other actors in synchronous way.
    The StageActorRef's lifecycle is bound to the operator, in other words when the operator is finished, the Actor will be terminated as well. The entity backing the StageActorRef is not a real Actor, but the GraphStageLogic itself, therefore it does not react to PoisonPill.
    To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.
    
    Parameters:
    
    receive - callback that will be called upon receiving of a message by this special Actor
    
    Returns:
    
    minimal actor with watch method
  - getEagerStageActor
```
protected GraphStageLogic.StageActor getEagerStageActor(Materializer eagerMaterializer,
                                                        scala.Function1<scala.Tuple2<ActorRef,java.lang.Object>,scala.runtime.BoxedUnit> receive)
```
    INTERNAL API
    To be thread safe this method must only be called from either the constructor of the graph operator during materialization or one of the methods invoked by the graph operator machinery, such as onPush and onPull.
  - stageActorName
```
protected java.lang.String stageActorName()
```
    Override and return a name to be given to the StageActor of this operator.
    This method will be only invoked and used once, during the first getStageActor(scala.Function1<scala.Tuple2<org.apache.pekko.actor.ActorRef,java.lang.Object>,scala.runtime.BoxedUnit>) invocation whichc reates the actor, since subsequent getStageActors calls function like become, rather than creating new actors.
    Returns an empty string by default, which means that the name will a unique generated String (e.g. "$$a").
  - beforePreStart
```
protected void beforePreStart()
```
    INTERNAL API
  - afterPostStop
```
protected void afterPostStop()
```
    INTERNAL API
  - preStart
```
public void preStart()
              throws java.lang.Exception
```
    Invoked before any external events are processed, at the startup of the operator.
    
    Throws:
    
    java.lang.Exception
  - postStop
```
public void postStop()
              throws java.lang.Exception
```
    Invoked after processing of external events stopped because the operator is about to stop or fail.
    
    Throws:
    
    java.lang.Exception
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object

Class GraphStageLogic

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

GraphStageLogic

Method Detail

inCount

outCount

materializer

subFusingMaterializer

eagerTerminateInput

ignoreTerminateInput

conditionalTerminateInput

totallyIgnorantInput

eagerTerminateOutput

ignoreTerminateOutput

conditionalTerminateOutput

setHandler

setHandlers

getHandler

setHandler

getHandler

pull

tryPull

cancel

cancel

grab

hasBeenPulled

isAvailable

isClosed

push

setKeepGoing

complete

fail

completeStage

cancelStage

failStage

isAvailable

isClosed

readN

readN

read

read

abortReading

emitMultiple

emitMultiple

emitMultiple

emitMultiple

emitMultiple

emitMultiple

emit

emit

emit

abortEmitting

passAlong

passAlong$default$3

passAlong$default$4

passAlong$default$5

getAsyncCallback

createAsyncCallback

stageActor

getStageActor

getEagerStageActor

stageActorName

beforePreStart

afterPostStop

preStart

postStop

toString