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Java auction example (#29443)

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Christopher Batey 2020-07-30 17:03:46 +01:00
parent 742352caba
commit c945fbd7a1
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22
akka-docs/src/main/paradox/typed/replicated-eventsourcing-examples.md
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@ -18,11 +18,17 @@ We model those operations as commands to be sent to the auction actor:
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #commands }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #commands }
The events:
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #events }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #events }
The winner does not have to pay the highest bid but only enough to beat the second highest so the `highestCounterOffer` is in the `AuctionFinished` event.
Let's have a look at the auction entity that will handle incoming commands:
@ -30,6 +36,9 @@ Let's have a look at the auction entity that will handle incoming commands:
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #command-handler }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #command-handler }
There is nothing specific to Replicated Event Sourcing about the command handler. It is the same as a command handler for a standard `EventSourcedBehavior`.
For `OfferBid` and `AuctionFinished` we do nothing more than to emit
events corresponding to the command. For `GetHighestBid` we respond with details from the state. Note, that we overwrite the actual
@ -43,21 +52,29 @@ an `initialBid`.
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #setup }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #setup }
@@@ div { .group-scala }
The auction moves through the following phases:
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #phase }
@@@
The closing and closed states are to model waiting for all replicas to see the result of the auction before
actually closing the action.
Let's have a look at our state class, `AuctionState` which also represents the CRDT in our example.
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #state }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #state }
The state consists of a flag that keeps track of whether the auction is still active, the currently highest bid,
and the highest counter offer so far.
@ -97,6 +114,9 @@ In the event handler above, when recovery is not running, it calls `eventTrigger
Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedAuctionExampleSpec.scala) { #event-triggers }
Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedAuctionExampleTest.java) { #event-triggers }
The event trigger uses the `ReplicationContext` to decide when to trigger the Finish of the action.
When a replica saves the `AuctionFinished` event it checks whether it should close the auction.
For the close to happen the replica must be the one designated to close and all replicas must have