=per #18219 Find plugin constructor automatically

akka-docs/rst/java/lambda-persistence.rst

@@ -763,6 +763,9 @@ The journal plugin instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism. 
 
+The journal plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.
+
 Don't run journal tasks/futures on the system default dispatcher, since that might starve other tasks. 
 
 Snapshot store plugin API
@@ -783,6 +786,9 @@ The snapshot store instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism.
 
+The snapshot store plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.
+
 Don't run snapshot store tasks/futures on the system default dispatcher, since that might starve other tasks.
 
 Pre-packaged plugins

akka-docs/rst/java/persistence.rst

@@ -713,6 +713,9 @@ The journal plugin instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism. 
 
+The journal plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.  
+
 Don't run journal tasks/futures on the system default dispatcher, since that might starve other tasks.
 
 Snapshot store plugin API
@@ -733,6 +736,9 @@ The snapshot store instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism.
 
+The snapshot store plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.
+
 Don't run snapshot store tasks/futures on the system default dispatcher, since that might starve other tasks.
 
 Plugin TCK

akka-docs/rst/scala/code/docs/persistence/PersistenceMultiDocSpec.scala

@@ -29,8 +29,6 @@ object PersistenceMultiDocSpec {
     class = "akka.persistence.chronicle.ChronicleSyncJournal"
     # Custom setting specific for the journal `ChronicleSyncJournal`.
     folder = ${user.dir}/store/journal
-    # Standard persistence extension property: plugin actor uses config injection.
-    inject-config = true
   }
   # Configuration entry for the custom snapshot store plugin, see `snapshotPluginId`.
   akka.persistence.chronicle.snapshot-store {
@@ -38,8 +36,6 @@ object PersistenceMultiDocSpec {
     class = "akka.persistence.chronicle.ChronicleSnapshotStore"
     # Custom setting specific for the snapshot store `ChronicleSnapshotStore`.
     folder = ${user.dir}/store/snapshot
-    # Standard persistence extension property: plugin actor uses config injection.
-    inject-config = true
   }
   //#override-config
   """

akka-docs/rst/scala/persistence.rst

@@ -773,6 +773,9 @@ The journal plugin instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism. 
 
+The journal plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.
+
 Don't run journal tasks/futures on the system default dispatcher, since that might starve other tasks.
 
 Snapshot store plugin API
@@ -793,6 +796,9 @@ The snapshot store instance is an actor so the methods corresponding to requests
 are executed sequentially. It may delegate to asynchronous libraries, spawn futures, or delegate to other
 actors to achive parallelism.
 
+The snapshot store plugin class must have a constructor without parameters or constructor with one ``com.typesafe.config.Config``
+parameter. The plugin section of the actor system's config will be passed in the config constructor parameter.
+
 Don't run snapshot store tasks/futures on the system default dispatcher, since that might starve other tasks.
 
 Plugin TCK

akka-persistence/src/main/resources/reference.conf

@@ -6,13 +6,15 @@
 # Make your edits in your application.conf in order to override these settings.
 
 # Note that both journal and snapshot store plugin configuration entries require few fields:
-# `class` : Fully qualified class name providing journal-plugin-api or snapshot-store-plugin-api implementation.
-# `inject-config` : Plugin actor has a constructor which expects plugin configuration entry. This boolean field is optional.
+# `class` : Fully qualified class name providing journal-plugin-api or snapshot-store-plugin-api implementation,
+#           The class must have a constructor without parameters or constructor with 
+#           one `com.typesafe.config.Config` parameter.
 # `plugin-dispatcher` : Absolute configuration path to the akka dispatcher configuration entry. This string field is optional.  
 
 # Note that journal and snapshot store plugins included with the extension are suitable for testing purposes only.
 # You should change extension defaults or override `journalPluginId` and `snapshotPluginId` in the persistent actor or view.
-# Directory of persistence journal and snapshot store plugins is available at the Akka Community Projects page http://akka.io/community/
+# Directory of persistence journal and snapshot store plugins is available at the Akka Community Projects page 
+# http://akka.io/community/
 
 # Default persistence extension settings.
 akka.persistence {
@@ -89,10 +91,6 @@ akka.persistence {
       # Dispatcher for message replay.
       replay-dispatcher = "akka.persistence.dispatchers.default-replay-dispatcher"
       
-      # Set this to true if plugin actor has a constructor which expects plugin 
-      # configuration entry.
-      inject-config = false
-      
       # Maximum size of a persistent message batch written to the journal.
       max-message-batch-size = 200
       
@@ -130,8 +128,6 @@ akka.persistence {
       # Dispatcher for the plugin actor.
       plugin-dispatcher = "akka.persistence.dispatchers.default-plugin-dispatcher"
       
-      inject-config = false
-
       circuit-breaker {
         max-failures = 5
         call-timeout = 20s

akka-persistence/src/main/scala/akka/persistence/Persistence.scala

@@ -14,6 +14,8 @@ import com.typesafe.config.Config
 import scala.annotation.tailrec
 import scala.concurrent.duration._
 import java.util.Locale
+import akka.util.Reflect
+import scala.util.control.NonFatal
 
 /**
  * Persistence configuration.
@@ -254,9 +256,11 @@ class Persistence(val system: ExtendedActorSystem) extends Extension {
     val pluginClassName = pluginConfig.getString("class")
     log.debug(s"Create plugin: $pluginActorName $pluginClassName")
     val pluginClass = system.dynamicAccess.getClassFor[Any](pluginClassName).get
-    val pluginInjectConfig = pluginConfig.getBoolean("inject-config")
     val pluginDispatcherId = pluginConfig.getString("plugin-dispatcher")
-    val pluginActorArgs = if (pluginInjectConfig) List(pluginConfig) else Nil
+    val pluginActorArgs = try {
+      Reflect.findConstructor(pluginClass, List(pluginConfig)) // will throw if not found
+      List(pluginConfig)
+    } catch { case NonFatal(_) ⇒ Nil } // otherwise use empty constructor
     val pluginActorProps = Props(Deploy(dispatcher = pluginDispatcherId), pluginClass, pluginActorArgs)
     system.systemActorOf(pluginActorProps, pluginActorName)
   }

akka-persistence/src/test/scala/akka/persistence/LoadPluginSpec.scala

@@ -0,0 +1,38 @@
+/**
+ * Copyright (C) 2015 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.persistence
+
+import akka.persistence.journal.inmem.InmemJournal
+import com.typesafe.config.Config
+import akka.testkit.ImplicitSender
+import akka.actor.Actor
+
+object LoadJournalSpec {
+
+  case object GetConfig
+
+  class JournalWithConfig(val config: Config) extends InmemJournal {
+    override def receivePluginInternal: Actor.Receive = {
+      case GetConfig ⇒ sender() ! config
+    }
+  }
+}
+
+class LoadJournalSpec extends PersistenceSpec(PersistenceSpec.config("inmem", "LoadJournalSpec", extraConfig = Some(
+  """
+  akka.persistence.journal.inmem.class = "akka.persistence.LoadJournalSpec$JournalWithConfig"
+  akka.persistence.journal.inmem.extra-property = 17
+  """))) with ImplicitSender {
+  import LoadJournalSpec._
+
+  "A journal with config parameter" must {
+    "be created with plugin config" in {
+      val journalRef = Persistence(system).journalFor("akka.persistence.journal.inmem")
+      journalRef ! GetConfig
+      expectMsgType[Config].getInt("extra-property") should be(17)
+    }
+  }
+}
+