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+per #15279 FSM for PersistentActor

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leonidb 2014-11-09 14:12:36 +02:00
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akka-docs/rst/java/lambda-persistence.rst
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@ -488,6 +488,61 @@ not accept more messages and it will throw ``AtLeastOnceDelivery.MaxUnconfirmedM
The default value can be configured with the ``akka.persistence.at-least-once-delivery.max-unconfirmed-messages``
configuration key. The method can be overridden by implementation classes to return non-default values.
.. _persistent-fsm-java-lambda:
Persistent FSM
==============
``AbstractPersistentFSMActor`` handles the incoming messages in an FSM like fashion.
Its internal state is persisted as a sequence of changes, later referred to as domain events.
Relationship between incoming messages, FSM's states and transitions, persistence of domain events is defined by a DSL.
A Simple Example
----------------
To demonstrate the features of the ``AbstractPersistentFSMActor``, consider an actor which represents a Web store customer.
The contract of our "WebStoreCustomerFSMActor" is that it accepts the following commands:
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-commands
``AddItem`` sent when the customer adds an item to a shopping cart
``Buy`` - when the customer finishes the purchase
``Leave`` - when the customer leaves the store without purchasing anything
``GetCurrentCart`` allows to query the current state of customer's shopping cart
The customer can be in one of the following states:
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-states
``LookingAround`` customer is browsing the site, but hasn't added anything to the shopping cart
``Shopping`` customer has recently added items to the shopping cart
``Inactive`` customer has items in the shopping cart, but hasn't added anything recently,
``Paid`` customer has purchased the items
.. note::
``AbstractPersistentFSMActor`` states must inherit from ``PersistentFsmActor.FSMState`` and implement the
``String identifier()`` method. This is required in order to simplify the serialization of FSM states.
String identifiers should be unique!
Customer's actions are "recorded" as a sequence of "domain events", which are persisted. Those events are replayed on actor's
start in order to restore the latest customer's state:
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-domain-events
Customer state data represents the items in customer's shopping cart:
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-states-data
Here is how everything is wired together:
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-fsm-body
.. note::
State data can only be modified directly on initialization. Later it's modified only as a result of applying domain events.
Override the ``applyEvent`` method to define how state data is affected by domain events, see the example below
.. includecode:: ../../../akka-persistence/src/test/java/akka/persistence/fsm/AbstractPersistentFsmActorTest.java#customer-apply-event
Storage plugins
===============