raboof/pekko
1
0
Fork 0
Code Issues Pull requests Projects Releases 6 Packages Wiki Activity Actions 11

Identical contents in scala/persistence-query.md and java/persistence-query.md

Browse source
This commit is contained in:
Richard Imaoka 2017-06-16 20:44:04 +09:00
parent 1d2748cad2
commit af3b3d3732
3 changed files with 214 additions and 56 deletions
Download patch file Download diff file Expand all files Collapse all files

138
akka-docs/src/main/paradox/java/persistence-query.md
View file

@ -14,15 +14,23 @@ recommend (in the spirit of CQRS) of splitting up the write/read sides into sepa
Akka persistence query is a separate jar file. Make sure that you have the following dependency in your project: Akka persistence query is a separate jar file. Make sure that you have the following dependency in your project:
@@@vars Scala
``` : @@@vars
<dependency> ```
<groupId>com.typesafe.akka</groupId> "com.typesafe.akka" %% "akka-persistence-query" % "$akka.version$"
<artifactId>akka-persistence-query_$scala.binary_version$</artifactId> ```
<version>$akka.version$</version> @@@
</dependency>
``` Java
@@@ : @@@vars
```
<dependency>
<groupId>com.typesafe.akka</groupId>
<artifactId>akka-persistence-query_$scala.binary_version$</artifactId>
<version>$akka.version$</version>
</dependency>
```
@@@
## Design overview ## Design overview
@ -44,10 +52,14 @@ Read journals are implemented as [Community plugins](http://akka.io/community/#p
databases). For example, given a library that provides a `akka.persistence.query.my-read-journal` obtaining the related databases). For example, given a library that provides a `akka.persistence.query.my-read-journal` obtaining the related
journal is as simple as: journal is as simple as:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #basic-usage } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #basic-usage }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #basic-usage }
Journal implementers are encouraged to put this identifier in a variable known to the user, such that one can access it via Journal implementers are encouraged to put this identifier in a variable known to the user, such that one can access it via
`getJournalFor(NoopJournal.class, NoopJournal.identifier)`, however this is not enforced. @scala[`readJournalFor[NoopJournal](NoopJournal.identifier)`]@java[`getJournalFor(NoopJournal.class, NoopJournal.identifier)`], however this is not enforced.
Read journal implementations are available as [Community plugins](http://akka.io/community/#plugins-to-akka-persistence-query). Read journal implementations are available as [Community plugins](http://akka.io/community/#plugins-to-akka-persistence-query).
@ -73,19 +85,31 @@ The predefined queries are:
By default this stream should be assumed to be a "live" stream, which means that the journal should keep emitting new By default this stream should be assumed to be a "live" stream, which means that the journal should keep emitting new
persistence ids as they come into the system: persistence ids as they come into the system:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-live } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-live }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-live }
If your usage does not require a live stream, you can use the `currentPersistenceIds` query: If your usage does not require a live stream, you can use the `currentPersistenceIds` query:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-snap } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-snap }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-snap }
#### EventsByPersistenceIdQuery and CurrentEventsByPersistenceIdQuery #### EventsByPersistenceIdQuery and CurrentEventsByPersistenceIdQuery
`eventsByPersistenceId` is a query equivalent to replaying a @ref:[PersistentActor](persistence.md#event-sourcing), `eventsByPersistenceId` is a query equivalent to replaying a @ref:[PersistentActor](persistence.md#event-sourcing),
however, since it is a stream it is possible to keep it alive and watch for additional incoming events persisted by the however, since it is a stream it is possible to keep it alive and watch for additional incoming events persisted by the
persistent actor identified by the given `persistenceId`. persistent actor identified by the given `persistenceId`.
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-persistent-id } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-persistent-id }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-persistent-id }
Most journals will have to revert to polling in order to achieve this, Most journals will have to revert to polling in order to achieve this,
which can typically be configured with a `refresh-interval` configuration property. which can typically be configured with a `refresh-interval` configuration property.
@ -104,7 +128,11 @@ Some journals may support tagging of events via an @ref:[Event Adapters](persist
`akka.persistence.journal.Tagged` with the given `tags`. The journal may support other ways of doing tagging - again, `akka.persistence.journal.Tagged` with the given `tags`. The journal may support other ways of doing tagging - again,
how exactly this is implemented depends on the used journal. Here is an example of such a tagging event adapter: how exactly this is implemented depends on the used journal. Here is an example of such a tagging event adapter:
@@snip [LeveldbPersistenceQueryDocTest.java]($code$/java/jdocs/persistence/query/LeveldbPersistenceQueryDocTest.java) { #tagger } Scala
: @@snip [LeveldbPersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/LeveldbPersistenceQueryDocSpec.scala) { #tagger }
Java
: @@snip [LeveldbPersistenceQueryDocTest.java]($code$/java/jdocs/persistence/query/LeveldbPersistenceQueryDocTest.java) { #tagger }
@@@ note @@@ note
@ -121,7 +149,11 @@ In the example below we query all events which have been tagged (we assume this
@ref:[EventAdapter](persistence.md#event-adapters), or that the journal is smart enough that it can figure out what we mean by this @ref:[EventAdapter](persistence.md#event-adapters), or that the journal is smart enough that it can figure out what we mean by this
tag - for example if the journal stored the events as json it may try to find those with the field `tag` set to this value etc.). tag - for example if the journal stored the events as json it may try to find those with the field `tag` set to this value etc.).
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-tag } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-tag }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-tag }
As you can see, we can use all the usual stream combinators available from @ref:[Streams](stream/index.md) on the resulting query stream, As you can see, we can use all the usual stream combinators available from @ref:[Streams](stream/index.md) on the resulting query stream,
including for example taking the first 10 and cancelling the stream. It is worth pointing out that the built-in `EventsByTag` including for example taking the first 10 and cancelling the stream. It is worth pointing out that the built-in `EventsByTag`
@ -141,11 +173,25 @@ stream, for example if it's finite or infinite, strictly ordered or not ordered
is defined as the second type parameter of the returned `Source`, which allows journals to provide users with their is defined as the second type parameter of the returned `Source`, which allows journals to provide users with their
specialised query object, as demonstrated in the sample below: specialised query object, as demonstrated in the sample below:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-types } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-types }
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-definition } Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-types }
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-usage }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-definition }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-definition }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-usage }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-usage }
## Performance and denormalization ## Performance and denormalization
@ -176,7 +222,11 @@ it may be more efficient or interesting to query it (instead of the source event
If the read datastore exposes a [Reactive Streams](http://reactive-streams.org) interface then implementing a simple projection If the read datastore exposes a [Reactive Streams](http://reactive-streams.org) interface then implementing a simple projection
is as simple as, using the read-journal and feeding it into the databases driver interface, for example like so: is as simple as, using the read-journal and feeding it into the databases driver interface, for example like so:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-rs } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-rs }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-rs }
### Materialize view using mapAsync ### Materialize view using mapAsync
@ -186,9 +236,18 @@ you may have to implement the write logic using plain functions or Actors instea
In case your write logic is state-less and you just need to convert the events from one data type to another In case your write logic is state-less and you just need to convert the events from one data type to another
before writing into the alternative datastore, then the projection is as simple as: before writing into the alternative datastore, then the projection is as simple as:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple-classes } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-simple-classes }
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple } Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple-classes }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-simple }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple }
### Resumable projections ### Resumable projections
@ -200,9 +259,18 @@ The example below additionally highlights how you would use Actors to implement
you need to do some complex logic that would be best handled inside an Actor before persisting the event you need to do some complex logic that would be best handled inside an Actor before persisting the event
into the other datastore: into the other datastore:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor-run } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor-run }
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor } Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor-run }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor }
<a id="read-journal-plugin-api"></a> <a id="read-journal-plugin-api"></a>
## Query plugins ## Query plugins
@ -227,18 +295,26 @@ their exposed semantics as well as handled query scenarios.
A read journal plugin must implement `akka.persistence.query.ReadJournalProvider` which A read journal plugin must implement `akka.persistence.query.ReadJournalProvider` which
creates instances of `akka.persistence.query.scaladsl.ReadJournal` and creates instances of `akka.persistence.query.scaladsl.ReadJournal` and
`akka.persistence.query.javaadsl.ReadJournal`. The plugin must implement both the `scaladsl` `akka.persistence.query.javaadsl.ReadJournal`. The plugin must implement both the `scaladsl`
and the `javadsl` interfaces because the `akka.stream.scaladsl.Source` and and the `javadsl` @scala[traits]@java[interfaces] because the `akka.stream.scaladsl.Source` and
`akka.stream.javadsl.Source` are different types and even though those types can easily be converted `akka.stream.javadsl.Source` are different types and even though those types can easily be converted
to each other it is most convenient for the end user to get access to the Java or Scala `Source` directly. to each other it is most convenient for the end user to get access to the Java or Scala `Source` directly.
As illustrated below one of the implementations can delegate to the other. As illustrated below one of the implementations can delegate to the other.
Below is a simple journal implementation: Below is a simple journal implementation:
@@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #my-read-journal } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #my-read-journal }
And the `EventsByTag` could be backed by such an Actor for example: Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #my-read-journal }
@@snip [MyEventsByTagJavaPublisher.java]($code$/java/jdocs/persistence/query/MyEventsByTagJavaPublisher.java) { #events-by-tag-publisher } And the `eventsByTag` could be backed by such an Actor for example:
Scala
: @@snip [MyEventsByTagPublisher.scala]($code$/scala/docs/persistence/query/MyEventsByTagPublisher.scala) { #events-by-tag-publisher }
Java
: @@snip [MyEventsByTagJavaPublisher.java]($code$/java/jdocs/persistence/query/MyEventsByTagJavaPublisher.java) { #events-by-tag-publisher }
The `ReadJournalProvider` class must have a constructor with one of these signatures: The `ReadJournalProvider` class must have a constructor with one of these signatures:
@ -254,7 +330,7 @@ If the underlying datastore only supports queries that are completed when they r
end of the "result set", the journal has to submit new queries after a while in order end of the "result set", the journal has to submit new queries after a while in order
to support "infinite" event streams that include events stored after the initial query to support "infinite" event streams that include events stored after the initial query
has completed. It is recommended that the plugin use a configuration property named has completed. It is recommended that the plugin use a configuration property named
`refresh-interval` for defining such a refresh interval. `refresh-interval` for defining such a refresh interval.
### Plugin TCK ### Plugin TCK

128
akka-docs/src/main/paradox/scala/persistence-query.md
View file

@ -14,11 +14,23 @@ recommend (in the spirit of CQRS) of splitting up the write/read sides into sepa
Akka persistence query is a separate jar file. Make sure that you have the following dependency in your project: Akka persistence query is a separate jar file. Make sure that you have the following dependency in your project:
@@@vars Scala
``` : @@@vars
"com.typesafe.akka" %% "akka-persistence-query" % "$akka.version$" ```
``` "com.typesafe.akka" %% "akka-persistence-query" % "$akka.version$"
@@@ ```
@@@
Java
: @@@vars
```
<dependency>
<groupId>com.typesafe.akka</groupId>
<artifactId>akka-persistence-query_$scala.binary_version$</artifactId>
<version>$akka.version$</version>
</dependency>
```
@@@
## Design overview ## Design overview
@ -40,10 +52,14 @@ Read journals are implemented as [Community plugins](http://akka.io/community/#p
databases). For example, given a library that provides a `akka.persistence.query.my-read-journal` obtaining the related databases). For example, given a library that provides a `akka.persistence.query.my-read-journal` obtaining the related
journal is as simple as: journal is as simple as:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #basic-usage } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #basic-usage }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #basic-usage }
Journal implementers are encouraged to put this identifier in a variable known to the user, such that one can access it via Journal implementers are encouraged to put this identifier in a variable known to the user, such that one can access it via
`readJournalFor[NoopJournal](NoopJournal.identifier)`, however this is not enforced. @scala[`readJournalFor[NoopJournal](NoopJournal.identifier)`]@java[`getJournalFor(NoopJournal.class, NoopJournal.identifier)`], however this is not enforced.
Read journal implementations are available as [Community plugins](http://akka.io/community/#plugins-to-akka-persistence-query). Read journal implementations are available as [Community plugins](http://akka.io/community/#plugins-to-akka-persistence-query).
@ -69,11 +85,19 @@ The predefined queries are:
By default this stream should be assumed to be a "live" stream, which means that the journal should keep emitting new By default this stream should be assumed to be a "live" stream, which means that the journal should keep emitting new
persistence ids as they come into the system: persistence ids as they come into the system:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-live } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-live }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-live }
If your usage does not require a live stream, you can use the `currentPersistenceIds` query: If your usage does not require a live stream, you can use the `currentPersistenceIds` query:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-snap } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #all-persistence-ids-snap }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #all-persistence-ids-snap }
#### EventsByPersistenceIdQuery and CurrentEventsByPersistenceIdQuery #### EventsByPersistenceIdQuery and CurrentEventsByPersistenceIdQuery
@ -81,7 +105,11 @@ If your usage does not require a live stream, you can use the `currentPersistenc
however, since it is a stream it is possible to keep it alive and watch for additional incoming events persisted by the however, since it is a stream it is possible to keep it alive and watch for additional incoming events persisted by the
persistent actor identified by the given `persistenceId`. persistent actor identified by the given `persistenceId`.
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-persistent-id } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-persistent-id }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-persistent-id }
Most journals will have to revert to polling in order to achieve this, Most journals will have to revert to polling in order to achieve this,
which can typically be configured with a `refresh-interval` configuration property. which can typically be configured with a `refresh-interval` configuration property.
@ -100,7 +128,11 @@ Some journals may support tagging of events via an @ref:[Event Adapters](persist
`akka.persistence.journal.Tagged` with the given `tags`. The journal may support other ways of doing tagging - again, `akka.persistence.journal.Tagged` with the given `tags`. The journal may support other ways of doing tagging - again,
how exactly this is implemented depends on the used journal. Here is an example of such a tagging event adapter: how exactly this is implemented depends on the used journal. Here is an example of such a tagging event adapter:
@@snip [LeveldbPersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/LeveldbPersistenceQueryDocSpec.scala) { #tagger } Scala
: @@snip [LeveldbPersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/LeveldbPersistenceQueryDocSpec.scala) { #tagger }
Java
: @@snip [LeveldbPersistenceQueryDocTest.java]($code$/java/jdocs/persistence/query/LeveldbPersistenceQueryDocTest.java) { #tagger }
@@@ note @@@ note
@ -117,7 +149,11 @@ In the example below we query all events which have been tagged (we assume this
@ref:[EventAdapter](persistence.md#event-adapters), or that the journal is smart enough that it can figure out what we mean by this @ref:[EventAdapter](persistence.md#event-adapters), or that the journal is smart enough that it can figure out what we mean by this
tag - for example if the journal stored the events as json it may try to find those with the field `tag` set to this value etc.). tag - for example if the journal stored the events as json it may try to find those with the field `tag` set to this value etc.).
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-tag } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #events-by-tag }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #events-by-tag }
As you can see, we can use all the usual stream combinators available from @ref:[Streams](stream/index.md) on the resulting query stream, As you can see, we can use all the usual stream combinators available from @ref:[Streams](stream/index.md) on the resulting query stream,
including for example taking the first 10 and cancelling the stream. It is worth pointing out that the built-in `EventsByTag` including for example taking the first 10 and cancelling the stream. It is worth pointing out that the built-in `EventsByTag`
@ -137,11 +173,25 @@ stream, for example if it's finite or infinite, strictly ordered or not ordered
is defined as the second type parameter of the returned `Source`, which allows journals to provide users with their is defined as the second type parameter of the returned `Source`, which allows journals to provide users with their
specialised query object, as demonstrated in the sample below: specialised query object, as demonstrated in the sample below:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-types } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-types }
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-definition } Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-types }
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-usage }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-definition }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-definition }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #advanced-journal-query-usage }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #advanced-journal-query-usage }
## Performance and denormalization ## Performance and denormalization
@ -172,7 +222,11 @@ it may be more efficient or interesting to query it (instead of the source event
If the read datastore exposes a [Reactive Streams](http://reactive-streams.org) interface then implementing a simple projection If the read datastore exposes a [Reactive Streams](http://reactive-streams.org) interface then implementing a simple projection
is as simple as, using the read-journal and feeding it into the databases driver interface, for example like so: is as simple as, using the read-journal and feeding it into the databases driver interface, for example like so:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-rs } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-rs }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-rs }
### Materialize view using mapAsync ### Materialize view using mapAsync
@ -182,7 +236,18 @@ you may have to implement the write logic using plain functions or Actors instea
In case your write logic is state-less and you just need to convert the events from one data type to another In case your write logic is state-less and you just need to convert the events from one data type to another
before writing into the alternative datastore, then the projection is as simple as: before writing into the alternative datastore, then the projection is as simple as:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-simple } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-simple-classes }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple-classes }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-simple }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-simple }
### Resumable projections ### Resumable projections
@ -194,9 +259,18 @@ The example below additionally highlights how you would use Actors to implement
you need to do some complex logic that would be best handled inside an Actor before persisting the event you need to do some complex logic that would be best handled inside an Actor before persisting the event
into the other datastore: into the other datastore:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor-run } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor-run }
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor } Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor-run }
Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #projection-into-different-store-actor }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #projection-into-different-store-actor }
<a id="read-journal-plugin-api"></a> <a id="read-journal-plugin-api"></a>
## Query plugins ## Query plugins
@ -221,18 +295,26 @@ their exposed semantics as well as handled query scenarios.
A read journal plugin must implement `akka.persistence.query.ReadJournalProvider` which A read journal plugin must implement `akka.persistence.query.ReadJournalProvider` which
creates instances of `akka.persistence.query.scaladsl.ReadJournal` and creates instances of `akka.persistence.query.scaladsl.ReadJournal` and
`akka.persistence.query.javaadsl.ReadJournal`. The plugin must implement both the `scaladsl` `akka.persistence.query.javaadsl.ReadJournal`. The plugin must implement both the `scaladsl`
and the `javadsl` traits because the `akka.stream.scaladsl.Source` and and the `javadsl` @scala[traits]@java[interfaces] because the `akka.stream.scaladsl.Source` and
`akka.stream.javadsl.Source` are different types and even though those types can easily be converted `akka.stream.javadsl.Source` are different types and even though those types can easily be converted
to each other it is most convenient for the end user to get access to the Java or Scala directly. to each other it is most convenient for the end user to get access to the Java or Scala `Source` directly.
As illustrated below one of the implementations can delegate to the other. As illustrated below one of the implementations can delegate to the other.
Below is a simple journal implementation: Below is a simple journal implementation:
@@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #my-read-journal } Scala
: @@snip [PersistenceQueryDocSpec.scala]($code$/scala/docs/persistence/query/PersistenceQueryDocSpec.scala) { #my-read-journal }
Java
: @@snip [PersistenceQueryDocTest.java]($code$/java/jdocs/persistence/PersistenceQueryDocTest.java) { #my-read-journal }
And the `eventsByTag` could be backed by such an Actor for example: And the `eventsByTag` could be backed by such an Actor for example:
@@snip [MyEventsByTagPublisher.scala]($code$/scala/docs/persistence/query/MyEventsByTagPublisher.scala) { #events-by-tag-publisher } Scala
: @@snip [MyEventsByTagPublisher.scala]($code$/scala/docs/persistence/query/MyEventsByTagPublisher.scala) { #events-by-tag-publisher }
Java
: @@snip [MyEventsByTagJavaPublisher.java]($code$/java/jdocs/persistence/query/MyEventsByTagJavaPublisher.java) { #events-by-tag-publisher }
The `ReadJournalProvider` class must have a constructor with one of these signatures: The `ReadJournalProvider` class must have a constructor with one of these signatures:

4
akka-docs/src/test/scala/docs/persistence/query/PersistenceQueryDocSpec.scala
View file

@ -308,11 +308,11 @@ class PersistenceQueryDocSpec(s: String) extends AkkaSpec(s) {
PersistenceQuery(system).readJournalFor[MyScaladslReadJournal]( PersistenceQuery(system).readJournalFor[MyScaladslReadJournal](
"akka.persistence.query.my-read-journal") "akka.persistence.query.my-read-journal")
//#projection-into-different-store-simple //#projection-into-different-store-simple-classes
trait ExampleStore { trait ExampleStore {
def save(event: Any): Future[Unit] def save(event: Any): Future[Unit]
} }
//#projection-into-different-store-simple //#projection-into-different-store-simple-classes
//#projection-into-different-store-simple //#projection-into-different-store-simple
val store: ExampleStore = ??? val store: ExampleStore = ???