java.lang.Object
- org.apache.pekko.stream.javadsl.Flow$

public class Flow$
extends java.lang.Object

Field Summary

Fields
Modifier and Type Field Description

static Flow$ MODULE$
Static reference to the singleton instance of this Scala object.

Constructor Summary

Constructors
Constructor Description

Flow$()

Method Summary

All Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>>`	`completionStageFlow(java.util.concurrent.CompletionStage<Flow<I,O,M>> flow)`	Turn a `CompletionStage` into a flow that will consume the values of the source when the future completes successfully.
`<T> Flow<T,T,NotUsed>`	`create()`	Create a `Flow` which can process elements of type `T`.
`<Out,In extends java.util.Optional<Out>> Flow<In,Out,NotUsed>`	`flattenOptional()`	Collect the value of `Optional` from the elements passing through this flow, empty `Optional` is filtered out.
`<I,O> Flow<I,O,NotUsed>`	`fromFunction(Function<I,O> f)`	Creates a [Flow] which will use the given function to transform its inputs to outputs.
`<I,O,M> Flow<I,O,M>`	`fromGraph(Graph<FlowShape<I,O>,M> g)`	A graph with the shape of a flow logically is a flow, this method makes it so also in type.
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>>`	`fromMaterializer(java.util.function.BiFunction<Materializer,Attributes,Flow<I,O,M>> factory)`	Defers the creation of a `Flow` until materialization.
`<I,O> Flow<I,O,NotUsed>`	`fromProcessor(Creator<org.reactivestreams.Processor<I,O>> processorFactory)`
`<I,O,Mat> Flow<I,O,Mat>`	`fromProcessorMat(Creator<Pair<org.reactivestreams.Processor<I,O>,Mat>> processorFactory)`
`<I,O> Flow<I,O,NotUsed>`	`fromSinkAndSource(Graph<SinkShape<I>,?> sink, Graph<SourceShape<O>,?> source)`	Creates a `Flow` from a `Sink` and a `Source` where the Flow's input will be sent to the Sink and the Flow's output will come from the Source.
`<I,O> Flow<I,O,NotUsed>`	`fromSinkAndSourceCoupled(Graph<SinkShape<I>,?> sink, Graph<SourceShape<O>,?> source)`	Allows coupling termination (cancellation, completion, erroring) of Sinks and Sources while creating a Flow from them.
`<I,O,M1,M2,M> Flow<I,O,M>`	`fromSinkAndSourceCoupledMat(Graph<SinkShape<I>,M1> sink, Graph<SourceShape<O>,M2> source, Function2<M1,M2,M> combine)`	Allows coupling termination (cancellation, completion, erroring) of Sinks and Sources while creating a Flow from them.
`<I,O,M1,M2,M> Flow<I,O,M>`	`fromSinkAndSourceMat(Graph<SinkShape<I>,M1> sink, Graph<SourceShape<O>,M2> source, Function2<M1,M2,M> combine)`	Creates a `Flow` from a `Sink` and a `Source` where the Flow's input will be sent to the Sink and the Flow's output will come from the Source.
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>>`	`lazyCompletionStageFlow(Creator<java.util.concurrent.CompletionStage<Flow<I,O,M>>> create)`	Defers invoking the `create` function to create a future flow until there downstream demand has caused upstream to send a first element.
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>>`	`lazyFlow(Creator<Flow<I,O,M>> create)`	Defers invoking the `create` function to create a future flow until there is downstream demand and passing that downstream demand upstream triggers the first element.
`<I,O,M> Flow<I,O,M>`	`lazyInit(Function<I,java.util.concurrent.CompletionStage<Flow<I,O,M>>> flowFactory, Creator<M> fallback)`	Deprecated. Use 'Flow.completionStageFlow' in combination with prefixAndTail(1) instead, see `completionStageFlow` operator docs for details.
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<java.util.Optional<M>>>`	`lazyInitAsync(Creator<java.util.concurrent.CompletionStage<Flow<I,O,M>>> flowFactory)`	Deprecated. Use 'Flow.lazyCompletionStageFlow' instead.
`<T> Flow<T,T,NotUsed>`	`of(java.lang.Class<T> clazz)`	Create a `Flow` which can process elements of type `T`.
`<FIn,FOut,FViaOut,FMat,FViaMat,Mat> Flow<FIn,java.util.Optional<FViaOut>,Mat>`	`optionalVia(Flow<FIn,java.util.Optional<FOut>,FMat> flow, Flow<FOut,FViaOut,FViaMat> viaFlow, Function2<FMat,FViaMat,Mat> combine)`	Creates a Flow from an existing base Flow outputting an optional element and applying an additional viaFlow only if the element in the stream is defined.
`<I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>>`	`setup(java.util.function.BiFunction<ActorMaterializer,Attributes,Flow<I,O,M>> factory)`	Deprecated. Use 'fromMaterializer' instead.
`<In,SuperOut,Out extends SuperOut,M> Flow<In,SuperOut,M>`	`upcast(Flow<In,Out,M> flow)`	Upcast a stream of elements to a stream of supertypes of that element.

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

Field Detail
- MODULE$
```
public static final Flow$ MODULE$
```
  Static reference to the singleton instance of this Scala object.

Constructor Detail
- Flow$
```
public Flow$()
```

Method Detail

create
```
public <T> Flow<T,T,NotUsed> create()
```
Create a `Flow` which can process elements of type `T`.

fromProcessor

public <I,O> Flow<I,O,NotUsed> fromProcessor(Creator<org.reactivestreams.Processor<I,O>> processorFactory)

fromProcessorMat

public <I,O,Mat> Flow<I,O,Mat> fromProcessorMat(Creator<Pair<org.reactivestreams.Processor<I,O>,Mat>> processorFactory)

fromFunction
```
public <I,O> Flow<I,O,NotUsed> fromFunction(Function<I,O> f)
```
Creates a [Flow] which will use the given function to transform its inputs to outputs. It is equivalent to Flow.create[T].map(f)

optionalVia
```
public <FIn,FOut,FViaOut,FMat,FViaMat,Mat> Flow<FIn,java.util.Optional<FViaOut>,Mat> optionalVia(Flow<FIn,java.util.Optional<FOut>,FMat> flow,
                                                                                                                                           Flow<FOut,FViaOut,FViaMat> viaFlow,
                                                                                                                                           Function2<FMat,FViaMat,Mat> combine)
```
Creates a Flow from an existing base Flow outputting an optional element and applying an additional viaFlow only if the element in the stream is defined.
'''Emits when''' the provided viaFlow runs with defined elements
'''Backpressures when''' the viaFlow runs for the defined elements and downstream backpressures
'''Completes when''' upstream completes
'''Cancels when''' downstream cancels

Parameters:

flow - The base flow that outputs an optional element

viaFlow - The flow that gets used if the optional element in is defined.

combine - How to combine the materialized values of flow and viaFlow

Returns:

a Flow with the viaFlow applied onto defined elements of the flow. The output value is contained within an Optional which indicates whether the original flow's element had viaFlow applied.

Since:

1.1.0

of

public <T> Flow<T,T,NotUsed> of(java.lang.Class<T> clazz)

Create a `Flow` which can process elements of type `T`.

fromGraph
```
public <I,O,M> Flow<I,O,M> fromGraph(Graph<FlowShape<I,O>,M> g)
```
A graph with the shape of a flow logically is a flow, this method makes it so also in type.

fromMaterializer
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>> fromMaterializer(java.util.function.BiFunction<Materializer,Attributes,Flow<I,O,M>> factory)
```
Defers the creation of a Flow until materialization. The factory function exposes Materializer which is going to be used during materialization and Attributes of the Flow returned by this method.

setup
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>> setup(java.util.function.BiFunction<ActorMaterializer,Attributes,Flow<I,O,M>> factory)
```
Deprecated.
Use 'fromMaterializer' instead. Since Akka 2.6.0.

Defers the creation of a Flow until materialization. The factory function exposes ActorMaterializer which is going to be used during materialization and Attributes of the Flow returned by this method.

fromSinkAndSource
```
public <I,O> Flow<I,O,NotUsed> fromSinkAndSource(Graph<SinkShape<I>,?> sink,
                                                                   Graph<SourceShape<O>,?> source)
```
Creates a Flow from a Sink and a Source where the Flow's input will be sent to the Sink and the Flow's output will come from the Source.
The resulting flow can be visualized as:
```
     +----------------------------------------------+
     | Resulting Flow[I, O, NotUsed]                |
     |                                              |
     |  +---------+                  +-----------+  |
     |  |         |                  |           |  |
 I  ~~> | Sink[I] | [no-connection!] | Source[O] | ~~> O
     |  |         |                  |           |  |
     |  +---------+                  +-----------+  |
     +----------------------------------------------+
 
```
The completion of the Sink and Source sides of a Flow constructed using this method are independent. So if the Sink receives a completion signal, the Source side will remain unaware of that. If you are looking to couple the termination signals of the two sides use Flow.fromSinkAndSourceCoupled instead.
See also <I,O,M1,M2,M>fromSinkAndSourceMat(org.apache.pekko.stream.Graph<org.apache.pekko.stream.SinkShape<I>,M1>,org.apache.pekko.stream.Graph<org.apache.pekko.stream.SourceShape<O>,M2>,org.apache.pekko.japi.function.Function2<M1,M2,M>) when access to materialized values of the parameters is needed.

fromSinkAndSourceMat

public <I,O,M1,M2,M> Flow<I,O,M> fromSinkAndSourceMat(Graph<SinkShape<I>,M1> sink,
                                                                                          Graph<SourceShape<O>,M2> source,
                                                                                          Function2<M1,M2,M> combine)

Creates a Flow from a Sink and a Source where the Flow's input will be sent to the Sink and the Flow's output will come from the Source.

The resulting flow can be visualized as:


     +-------------------------------------------------------+
     | Resulting Flow[I, O, M]                              |
     |                                                      |
     |  +-------------+                  +---------------+  |
     |  |             |                  |               |  |
 I  ~~> | Sink[I, M1] | [no-connection!] | Source[O, M2] | ~~> O
     |  |             |                  |               |  |
     |  +-------------+                  +---------------+  |
     +------------------------------------------------------+

The completion of the Sink and Source sides of a Flow constructed using this method are independent. So if the Sink receives a completion signal, the Source side will remain unaware of that. If you are looking to couple the termination signals of the two sides use Flow.fromSinkAndSourceCoupledMat instead.

The combine function is used to compose the materialized values of the sink and source into the materialized value of the resulting Flow.

fromSinkAndSourceCoupled

public <I,O> Flow<I,O,NotUsed> fromSinkAndSourceCoupled(Graph<SinkShape<I>,?> sink,
                                                                          Graph<SourceShape<O>,?> source)

Allows coupling termination (cancellation, completion, erroring) of Sinks and Sources while creating a Flow from them. Similar to Flow.fromSinkAndSource however couples the termination of these two operators.

The resulting flow can be visualized as:


     +---------------------------------------------+
     | Resulting Flow[I, O, NotUsed]               |
     |                                             |
     |  +---------+                 +-----------+  |
     |  |         |                 |           |  |
 I  ~~> | Sink[I] | ~~~(coupled)~~~ | Source[O] | ~~> O
     |  |         |                 |           |  |
     |  +---------+                 +-----------+  |
     +---------------------------------------------+

E.g. if the emitted Flow gets a cancellation, the Source of course is cancelled, however the Sink will also be completed. The table below illustrates the effects in detail:

Returned Flow	Sink (`in`)	Source (`out`)
cause: upstream (sink-side) receives completion	effect: receives completion	effect: receives cancel
cause: upstream (sink-side) receives error	effect: receives error	effect: receives cancel
cause: downstream (source-side) receives cancel	effect: completes	effect: receives cancel
effect: cancels upstream, completes downstream	effect: completes	cause: signals complete
effect: cancels upstream, errors downstream	effect: receives error	cause: signals error or throws
effect: cancels upstream, completes downstream	cause: cancels	effect: receives cancel

fromSinkAndSourceCoupledMat

public <I,O,M1,M2,M> Flow<I,O,M> fromSinkAndSourceCoupledMat(Graph<SinkShape<I>,M1> sink,
                                                                                                 Graph<SourceShape<O>,M2> source,
                                                                                                 Function2<M1,M2,M> combine)

Allows coupling termination (cancellation, completion, erroring) of Sinks and Sources while creating a Flow from them. Similar to Flow.fromSinkAndSource however couples the termination of these two operators.

The resulting flow can be visualized as:


     +-----------------------------------------------------+
     | Resulting Flow[I, O, M]                             |
     |                                                     |
     |  +-------------+                 +---------------+  |
     |  |             |                 |               |  |
 I  ~~> | Sink[I, M1] | ~~~(coupled)~~~ | Source[O, M2] | ~~> O
     |  |             |                 |               |  |
     |  +-------------+                 +---------------+  |
     +-----------------------------------------------------+

E.g. if the emitted Flow gets a cancellation, the Source of course is cancelled, however the Sink will also be completed. The table on Flow.fromSinkAndSourceCoupled illustrates the effects in detail.

The combine function is used to compose the materialized values of the sink and source into the materialized value of the resulting Flow.

lazyInit
```
public <I,O,M> Flow<I,O,M> lazyInit(Function<I,java.util.concurrent.CompletionStage<Flow<I,O,M>>> flowFactory,
                                                            Creator<M> fallback)
```
Deprecated.
Use 'Flow.completionStageFlow' in combination with prefixAndTail(1) instead, see `completionStageFlow` operator docs for details. Since Akka 2.6.0.

Creates a real Flow upon receiving the first element. Internal Flow will not be created if there are no elements, because of completion, cancellation, or error.
The materialized value of the Flow is the value that is created by the fallback function.
'''Emits when''' the internal flow is successfully created and it emits
'''Backpressures when''' the internal flow is successfully created and it backpressures
'''Completes when''' upstream completes and all elements have been emitted from the internal flow
'''Cancels when''' downstream cancels

lazyInitAsync
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<java.util.Optional<M>>> lazyInitAsync(Creator<java.util.concurrent.CompletionStage<Flow<I,O,M>>> flowFactory)
```
Deprecated.
Use 'Flow.lazyCompletionStageFlow' instead. Since Akka 2.6.0.

Creates a real Flow upon receiving the first element. Internal Flow will not be created if there are no elements, because of completion, cancellation, or error.
The materialized value of the Flow is a Future[Option[M} that is completed with Some(mat) when the internal flow gets materialized or with None when there where no elements. If the flow materialization (including the call of the flowFactory) fails then the future is completed with a failure.
'''Emits when''' the internal flow is successfully created and it emits
'''Backpressures when''' the internal flow is successfully created and it backpressures
'''Completes when''' upstream completes and all elements have been emitted from the internal flow
'''Cancels when''' downstream cancels

completionStageFlow
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>> completionStageFlow(java.util.concurrent.CompletionStage<Flow<I,O,M>> flow)
```
Turn a CompletionStage into a flow that will consume the values of the source when the future completes successfully. If the Future is completed with a failure the stream is failed.
The materialized completion stage value is completed with the materialized value of the future flow or failed with a NeverMaterializedException if upstream fails or downstream cancels before the completion stage has completed.

lazyFlow
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>> lazyFlow(Creator<Flow<I,O,M>> create)
```
Defers invoking the create function to create a future flow until there is downstream demand and passing that downstream demand upstream triggers the first element.
Note that asynchronous boundaries (and other operators) in the stream may do pre-fetching which counter acts the laziness and can trigger the factory earlier than expected.
'''Emits when''' the internal flow is successfully created and it emits
'''Backpressures when''' the internal flow is successfully created and it backpressures or downstream backpressures
'''Completes when''' upstream completes and all elements have been emitted from the internal flow
'''Cancels when''' downstream cancels

lazyCompletionStageFlow
```
public <I,O,M> Flow<I,O,java.util.concurrent.CompletionStage<M>> lazyCompletionStageFlow(Creator<java.util.concurrent.CompletionStage<Flow<I,O,M>>> create)
```
Defers invoking the create function to create a future flow until there downstream demand has caused upstream to send a first element.
The materialized future value is completed with the materialized value of the created flow when that has successfully been materialized.
If the create function throws or returns a future that fails the stream is failed, in this case the materialized future value is failed with a NeverMaterializedException.
Note that asynchronous boundaries (and other operators) in the stream may do pre-fetching which counter acts the laziness and can trigger the factory earlier than expected.
'''Emits when''' the internal flow is successfully created and it emits
'''Backpressures when''' the internal flow is successfully created and it backpressures or downstream backpressures
'''Completes when''' upstream completes and all elements have been emitted from the internal flow
'''Cancels when''' downstream cancels

upcast
```
public <In,SuperOut,Out extends SuperOut,M> Flow<In,SuperOut,M> upcast(Flow<In,Out,M> flow)
```
Upcast a stream of elements to a stream of supertypes of that element. Useful in combination with fan-in operators where you do not want to pay the cost of casting each element in a map.

Returns:

A flow that accepts In and outputs elements of the super type

flattenOptional
```
public <Out,In extends java.util.Optional<Out>> Flow<In,Out,NotUsed> flattenOptional()
```
Collect the value of Optional from the elements passing through this flow, empty Optional is filtered out.
Adheres to the ActorAttributes.SupervisionStrategy attribute.
'''Emits when''' the current Optional's value is present.
'''Backpressures when''' the value of the current Optional is present and downstream backpressures
'''Completes when''' upstream completes
'''Cancels when''' downstream cancels *

Class Flow$

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MODULE$

Constructor Detail

Flow$

Method Detail

create

fromProcessor

fromProcessorMat

fromFunction

optionalVia

of

fromGraph

fromMaterializer

setup

fromSinkAndSource

fromSinkAndSourceMat

fromSinkAndSourceCoupled

fromSinkAndSourceCoupledMat

lazyInit

lazyInitAsync

completionStageFlow

lazyFlow

lazyCompletionStageFlow

upcast

flattenOptional