Initial implementation of DurableStateStore and one test

akka-persistence/src/main/scala/akka/persistence/state/inmem/InmemDurableStateStoreProvider.scala

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+/*
+ * Copyright (C) 2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.state.inmem
+
+import akka.persistence.state.DurableStateStoreProvider
+import akka.persistence.state.scaladsl.DurableStateStore
+import akka.persistence.state.inmem.scaladsl.InmemDurableStateStore
+import akka.persistence.state.javadsl.{ DurableStateStore => JDurableStateStore }
+import akka.persistence.state.inmem.javadsl.{ InmemDurableStateStore => JInmemDurableStateStore }
+
+class InmemDurableStateStoreProvider extends DurableStateStoreProvider {
+  override def scaladslDurableStateStore(): DurableStateStore[Any] =
+    new InmemDurableStateStore[Any]
+
+  override def javadslDurableStateStore(): JDurableStateStore[AnyRef] =
+    new JInmemDurableStateStore[AnyRef]
+}

akka-persistence/src/main/scala/akka/persistence/state/inmem/javadsl/InmemDurableStateStore.scala

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+/*
+ * Copyright (C) 2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.state.inmem.javadsl
+
+import java.util.Optional
+import java.util.concurrent.{ CompletionStage, ConcurrentHashMap }
+
+import scala.concurrent.Future
+import scala.compat.java8.FutureConverters._
+
+import akka.Done
+
+import akka.persistence.state.javadsl.{ DurableStateUpdateStore, GetObjectResult }
+
+class InmemDurableStateStore[A] extends DurableStateUpdateStore[A] {
+  val store = new ConcurrentHashMap[String, A]()
+
+  def getObject(persistenceId: String): CompletionStage[GetObjectResult[A]] =
+    toJava(Future.successful(GetObjectResult(Optional.ofNullable(store.get(persistenceId)), 0)))
+
+  def upsertObject(persistenceId: String, seqNr: Long, value: A, tag: String): CompletionStage[Done] =
+    toJava(Future.successful(store.put(persistenceId, value) match {
+      case _ => Done
+    }))
+
+  def deleteObject(persistenceId: String): CompletionStage[Done] =
+    toJava(Future.successful(store.remove(persistenceId) match {
+      case _ => Done
+    }))
+}

akka-persistence/src/main/scala/akka/persistence/state/inmem/scaladsl/InmemDurableStateStore.scala

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+/*
+ * Copyright (C) 2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.state.inmem.scaladsl
+
+import scala.collection.concurrent.TrieMap
+import scala.concurrent.Future
+
+import akka.Done
+import akka.persistence.state.scaladsl.{ DurableStateUpdateStore, GetObjectResult }
+
+class InmemDurableStateStore[A] extends DurableStateUpdateStore[A] {
+  val store = new TrieMap[String, A]()
+
+  def getObject(persistenceId: String): Future[GetObjectResult[A]] =
+    Future.successful(GetObjectResult(store.get(persistenceId), 0))
+
+  def upsertObject(persistenceId: String, seqNr: Long, value: A, tag: String): Future[Done] =
+    Future.successful(store.put(persistenceId, value) match {
+      case _ => Done
+    })
+
+  def deleteObject(persistenceId: String): Future[Done] =
+    Future.successful(store.remove(persistenceId) match {
+      case _ => Done
+    })
+}