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!str #16168: Expose materialized value in the graph as a "source"

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Endre Sándor Varga 2015-03-30 14:22:12 +02:00
parent 37aa2cb886
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33 changed files with 601 additions and 173 deletions
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3
akka-docs-dev/rst/java/stream-flows-and-basics.rst
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@ -206,6 +206,9 @@ resulting values. Some examples of using these combiners are illustrated in the
.. includecode:: ../../../akka-samples/akka-docs-java-lambda/src/test/java/docs/stream/FlowDocTest.java#flow-mat-combine
.. note::
In Graphs it is possible to access the materialized value from inside the stream processing graph. For details see
:ref:`graph-matvalue-java`
Stream ordering
===============

18
akka-docs-dev/rst/java/stream-graphs.rst
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@ -194,6 +194,24 @@ together and also turned around with the ``.reversed()`` method. The test
simulates both parties of a network communication protocol without actually
having to open a network connection—the flows can just be connected directly.
.. _graph-matvalue-java:
Accessing the materialized value inside the Graph
-------------------------------------------------
In certain cases it might be necessary to feed back the materialized value of a Graph (partial, closed or backing a
Source, Sink, Flow or BidiFlow). This is possible by using ``builder.matValue`` which gives an ``Outlet`` that
can be used in the graph as an ordinary source or outlet, and which will eventually emit the materialized value.
If the materialized value is needed at more than one place, it is possible to call ``matValue`` any number of times
to acquire the necessary number of outlets.
.. includecode:: ../../../akka-samples/akka-docs-java-lambda/src/test/java/docs/stream/FlowGraphDocTest.java#flow-graph-matvalue
Be careful not to introduce a cycle where the materialized value actually contributes to the materialized value.
The following example demonstrates a case where the materialized ``Future`` of a fold is fed back to the fold itself.
.. includecode:: ../../../akka-samples/akka-docs-java-lambda/src/test/java/docs/stream/FlowGraphDocTest.java#flow-graph-matvalue-cycle
.. _graph-cycles-java:
Graph cycles, liveness and deadlocks