akka.projection.jdbc.scaladsl.JdbcHandler.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2020-2023 Lightbend Inc.
*/
package akka.projection.jdbc.scaladsl
import akka.projection.jdbc.JdbcHandlerLifecycle
import akka.projection.jdbc.JdbcSession
/**
* Implement this interface for the Envelope handler for Jdbc Projections.
*
* It can be stateful, with variables and mutable data structures.
* It is invoked by the `Projection` machinery one envelope at a time and visibility
* guarantees between the invocations are handled automatically, i.e. no volatile or
* other concurrency primitives are needed for managing the state.
*
* Supported error handling strategies for when processing an `Envelope` fails can be
* defined in configuration or using the `withRecoveryStrategy` method of a `Projection`
* implementation.
*/
trait JdbcHandler[Envelope, S <: JdbcSession] extends JdbcHandlerLifecycle {
/**
* The `process` method is invoked for each `Envelope`. Each time a new [[JdbcSession]] is passed with a new open transaction.
* It's allowed to run any blocking JDBC operation inside this method.
*
* One envelope is processed at a time. It will not be invoked with the next envelope until after this method returns.
*/
def process(session: S, envelope: Envelope): Unit
}
object JdbcHandler {
/** JdbcHandler that can be define from a simple function */
private class JdbcHandlerFunction[Envelope, S <: JdbcSession](handler: (S, Envelope) => Unit)
extends JdbcHandler[Envelope, S] {
override def process(session: S, envelope: Envelope): Unit = handler(session, envelope)
}
def apply[S <: JdbcSession, Envelope](handler: (S, Envelope) => Unit): JdbcHandler[Envelope, S] =
new JdbcHandlerFunction(handler)
}