com.lightbend.lagom.javadsl.persistence.cassandra

Class CassandraReadSideProcessor<Event extends AggregateEvent<Event>>

Object

com.lightbend.lagom.javadsl.persistence.cassandra.CassandraReadSideProcessor<Event>

public abstract class CassandraReadSideProcessor<Event extends AggregateEvent<Event>>
extends Object

Consume events produced by PersistentEntity instances and update one or more tables in Cassandra that are optimized for queries. The events belong to a AggregateEventTag, e.g. all persistent events of all Order entities.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	CassandraReadSideProcessor.EventHandlers
class	CassandraReadSideProcessor.EventHandlersBuilder Mutable builder for defining event handlers.

Constructor Summary

Constructors

Constructor and Description
CassandraReadSideProcessor()

Method Summary

Modifier and Type	Method and Description
abstract AggregateEventTag<Event>	aggregateTag() The processed events belong to a AggregateEventTag that is specified by this method, e.g.
java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>>	completedStatement(com.datastax.driver.core.BoundStatement stmt) Convenience method to create an already completed CompletionStage with one BoundStatement.
java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>>	completedStatements(java.util.List<com.datastax.driver.core.BoundStatement> stmts) Convenience method to create an already completed CompletionStage with several BoundStatement.
abstract CassandraReadSideProcessor.EventHandlers	defineEventHandlers(com.lightbend.lagom.javadsl.persistence.cassandra.CassandraReadSideProcessor.EventHandlersBuilder builder) Define the event handlers that are to be used.
java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>>	emptyStatements() Convenience method to create an already completed CompletionStage with zero BoundStatement.
java.util.concurrent.CompletionStage<java.util.Optional<java.util.UUID>>	noOffset()
abstract java.util.concurrent.CompletionStage<java.util.Optional<java.util.UUID>>	prepare(CassandraSession session) First you must tell where in the event stream the processing should start, i.e.

Methods inherited from class Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CassandraReadSideProcessor

public CassandraReadSideProcessor()

Method Detail

aggregateTag

public abstract AggregateEventTag<Event> aggregateTag()

The processed events belong to a AggregateEventTag that is specified by this method, e.g. all persistent events of all Order entities.

prepare

public abstract java.util.concurrent.CompletionStage<java.util.Optional<java.util.UUID>> prepare(CassandraSession session)

First you must tell where in the event stream the processing should start, i.e. return the offset. The current offset is a parameter to the event handler for each event and it should typically be stored so that it can be restored with a select statement here. Use the CassandraSession to get the stored offset.

Other things that is typically performed in this method is to create prepared statements that are later used when processing the events. Use CassandraSession.prepare(java.lang.String) to create the prepared statements.

Return noOffset() if you want to processes all events, e.g. when starting the first time or if the number of events are known to be small enough to processes all events.

defineEventHandlers

public abstract CassandraReadSideProcessor.EventHandlers defineEventHandlers(com.lightbend.lagom.javadsl.persistence.cassandra.CassandraReadSideProcessor.EventHandlersBuilder builder)

Define the event handlers that are to be used. Use the supplied builder to define the event handlers. One handler for each event class. A handler is a BiFunction that takes the event and the offset as parameters and returns zero or more bound statements that will be executed before processing next event.

completedStatement

public final java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>> completedStatement(com.datastax.driver.core.BoundStatement stmt)

Convenience method to create an already completed CompletionStage with one BoundStatement.

completedStatements

public final java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>> completedStatements(java.util.List<com.datastax.driver.core.BoundStatement> stmts)

Convenience method to create an already completed CompletionStage with several BoundStatement.

emptyStatements

public final java.util.concurrent.CompletionStage<java.util.List<com.datastax.driver.core.BoundStatement>> emptyStatements()

Convenience method to create an already completed CompletionStage with zero BoundStatement.

noOffset

public final java.util.concurrent.CompletionStage<java.util.Optional<java.util.UUID>> noOffset()