!cdd #17770 Use self recursive type in AbstractReplicatedData (Java API)

* complete the TwoPhaseSet java sample with serialization

akka-docs/rst/scala/code/docs/ddata/DistributedDataDocSpec.scala

@@ -33,6 +33,17 @@ object DistributedDataDocSpec {
       }
     }
     #//#serializer-config
+
+    #//#japi-serializer-config
+    akka.actor {
+      serializers {
+        twophaseset = "docs.ddata.japi.protobuf.TwoPhaseSetSerializer"
+      }
+      serialization-bindings {
+        "docs.ddata.japi.TwoPhaseSet" = twophaseset
+      }
+    }
+    #//#japi-serializer-config
     """
 
   //#data-bot
@@ -391,4 +402,14 @@ class DistributedDataDocSpec extends AkkaSpec(DistributedDataDocSpec.config) {
     s1 should be(s1)
   }
 
+  "test japi.TwoPhaseSetSerializer" in {
+    import scala.collection.JavaConverters._
+    val s1 = japi.TwoPhaseSet.create().add("a").add("b").add("c").remove("b")
+    s1.getElements.asScala should be(Set("a", "c"))
+    val serializer = SerializationExtension(system).findSerializerFor(s1)
+    val blob = serializer.toBinary(s1)
+    val s2 = serializer.fromBinary(blob, None)
+    s1 should be(s1)
+  }
+
 }

akka-docs/rst/scala/code/docs/ddata/TwoPhaseSet.scala

@@ -23,7 +23,7 @@ case class TwoPhaseSet(
 
   override def merge(that: TwoPhaseSet): TwoPhaseSet =
     copy(
-      adds = GSet(this.adds.elements ++ that.adds.elements),
-      removals = GSet(this.removals.elements ++ that.removals.elements))
+      adds = this.adds.merge(that.adds),
+      removals = this.removals.merge(that.removals))
 }
 //#twophaseset