Handle null constructor parameters, see #3486

akka-actor-tests/src/test/java/akka/actor/JavaAPI.java

@@ -12,6 +12,7 @@ import akka.routing.FromConfig;
 import akka.routing.NoRouter;
 import akka.testkit.AkkaJUnitActorSystemResource;
 import akka.testkit.AkkaSpec;
+import akka.testkit.TestProbe;
 
 import org.junit.ClassRule;
 import org.junit.Test;
@@ -20,8 +21,8 @@ import static org.junit.Assert.*;
 public class JavaAPI {
 
   @ClassRule
-  public static AkkaJUnitActorSystemResource actorSystemResource =
-    new AkkaJUnitActorSystemResource("JAvaAPI", AkkaSpec.testConf());
+  public static AkkaJUnitActorSystemResource actorSystemResource = new AkkaJUnitActorSystemResource("JavaAPI",
+      AkkaSpec.testConf());
 
   private final ActorSystem system = actorSystemResource.getSystem();
 
@@ -57,4 +58,95 @@ public class JavaAPI {
     }));
     assertNotNull(ref);
   }
+
+  @Test
+  public void mustBeAbleToCreateActorWIthConstructorParams() {
+    ActorRef ref = system.actorOf(Props.create(ActorWithConstructorParams.class, "a", "b", new Integer(17), 18));
+    final TestProbe probe = new TestProbe(system);
+    probe.send(ref, "get");
+    probe.expectMsg("a-b-17-18");
+  }
+
+  @Test
+  public void mustBeAbleToCreateActorWIthBoxedAndUnBoxedConstructorParams() {
+    ActorRef ref = system.actorOf(Props.create(ActorWithConstructorParams.class, "a", "b", 17, new Integer(18)));
+    final TestProbe probe = new TestProbe(system);
+    probe.send(ref, "get");
+    probe.expectMsg("a-b-17-18");
+  }
+
+  @Test
+  public void mustBeAbleToCreateActorWIthNullConstructorParams() {
+    ActorRef ref = system.actorOf(Props.create(ActorWithConstructorParams.class, "a", null, null, 18));
+    final TestProbe probe = new TestProbe(system);
+    probe.send(ref, "get");
+    probe.expectMsg("a-null-null-18");
+  }
+
+  @Test
+  public void mustBeAbleToCreateActorWIthNullConstructorParams2() {
+    // without this Object array wrapper it will not compile: "reference to create is ambiguous"
+    ActorRef ref = system.actorOf(Props.create(ActorWithConstructorParams.class, new Object[] { null }));
+    final TestProbe probe = new TestProbe(system);
+    probe.send(ref, "get");
+    probe.expectMsg("null-undefined-0-0");
+  }
+
+  @Test
+  public void mustBeAbleToCreateActorWIthNullConstructorParams3() {
+    ActorRef ref = system.actorOf(Props.create(ActorWithConstructorParams.class, "a", null));
+    final TestProbe probe = new TestProbe(system);
+    probe.send(ref, "get");
+    probe.expectMsg("a-null-0-0");
+  }
+
+  public static class ActorWithConstructorParams extends UntypedActor {
+
+    private final String a;
+    private final String b;
+    private final Integer c;
+    private final int d;
+
+    public ActorWithConstructorParams(String a, String b, Integer c, int d) {
+      this.a = a;
+      this.b = b;
+      this.c = c;
+      this.d = d;
+    }
+
+    public ActorWithConstructorParams(String a, Object b) {
+      this.a = a;
+      this.b = String.valueOf(b);
+      this.c = 0;
+      this.d = 0;
+    }
+
+    public ActorWithConstructorParams(String a, int d) {
+      this.a = a;
+      this.b = "undefined";
+      this.c = 0;
+      this.d = d;
+    }
+
+    public ActorWithConstructorParams(Object a) {
+      this.a = String.valueOf(a);
+      this.b = "undefined";
+      this.c = 0;
+      this.d = 0;
+    }
+
+    public ActorWithConstructorParams(int d) {
+      this.a = "undefined";
+      this.b = "undefined";
+      this.c = 0;
+      this.d = d;
+    }
+
+    @Override
+    public void onReceive(Object msg) {
+      String reply = String.valueOf(a) + "-" + String.valueOf(b) + "-" + String.valueOf(c) + "-" + String.valueOf(d);
+      getSender().tell(reply, getSelf());
+    }
+  }
+
 }

akka-actor/src/main/scala/akka/util/Reflect.scala

@@ -65,7 +65,7 @@ private[akka] object Reflect {
     try constructor.newInstance(args.asInstanceOf[Seq[AnyRef]]: _*)
     catch {
       case e: IllegalArgumentException ⇒
-        val argString = args map (_.getClass) mkString ("[", ", ", "]")
+        val argString = args map safeGetClass mkString ("[", ", ", "]")
         throw new IllegalArgumentException(s"constructor $constructor is incompatible with arguments $argString", e)
     }
   }
@@ -77,20 +77,25 @@ private[akka] object Reflect {
    */
   private[akka] def findConstructor[T](clazz: Class[T], args: immutable.Seq[Any]): Constructor[T] = {
     def error(msg: String): Nothing = {
-      val argClasses = args map (_.getClass) mkString ", "
+      val argClasses = args map safeGetClass mkString ", "
       throw new IllegalArgumentException(s"$msg found on $clazz for arguments [$argClasses]")
     }
     val candidates =
       clazz.getDeclaredConstructors filter (c ⇒
         c.getParameterTypes.length == args.length &&
           (c.getParameterTypes zip args forall {
-            case (found, required) ⇒ found.isInstance(required) || BoxedType(found).isInstance(required)
+            case (found, required) ⇒
+              found.isInstance(required) || BoxedType(found).isInstance(required) ||
+                (required == null && !found.isPrimitive)
           }))
     if (candidates.size == 1) candidates.head.asInstanceOf[Constructor[T]]
     else if (candidates.size > 1) error("multiple matching constructors")
     else error("no matching constructor")
   }
 
+  private def safeGetClass(a: Any): Class[_] =
+    if (a == null) classOf[AnyRef] else a.getClass
+
   /**
    * INTERNAL API
    * @param clazz the class which to instantiate an instance of