+per #3641 Storage plugin API

- Journal plugin API for storage backends with asynchronous client API (default impl: in-memory journal)
- Journal plugin API for storage backends with synchronous client API (default impl: LevelDB journal)
- Snapshot store plugin API (default impl: local filesystem snapshot store)

akka-persistence/src/main/scala/akka/persistence/journal/japi/SyncWriteJournal.scala

@@ -0,0 +1,48 @@
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.persistence.journal.japi
+
+import akka.persistence.journal.{ SyncWriteJournal ⇒ SSyncWriteJournal }
+import akka.persistence.PersistentImpl
+
+/**
+ * Java API.
+ *
+ * Abstract journal, optimized for synchronous writes.
+ */
+abstract class SyncWriteJournal extends AsyncReplay with SSyncWriteJournal {
+  final def write(persistent: PersistentImpl) =
+    doWrite(persistent)
+
+  final def delete(persistent: PersistentImpl) =
+    doDelete(persistent)
+
+  final def confirm(processorId: String, sequenceNr: Long, channelId: String) =
+    doConfirm(processorId, sequenceNr, channelId)
+
+  /**
+   * Plugin Java API.
+   *
+   * Synchronously writes a `persistent` message to the journal.
+   */
+  @throws(classOf[Exception])
+  def doWrite(persistent: PersistentImpl): Unit
+
+  /**
+   * Plugin Java API.
+   *
+   * Synchronously marks a `persistent` message as deleted.
+   */
+  @throws(classOf[Exception])
+  def doDelete(persistent: PersistentImpl): Unit
+
+  /**
+   * Plugin Java API.
+   *
+   * Synchronously writes a delivery confirmation to the journal.
+   */
+  @throws(classOf[Exception])
+  def doConfirm(processorId: String, sequenceNr: Long, channelId: String): Unit
+}