ActorContext.getParent for Java API #22413

akka-docs/rst/java/code/jdocs/cluster/TransformationBackend.java

@@ -0,0 +1,56 @@
+package jdocs.cluster;
+
+import static jdocs.cluster.TransformationMessages.BACKEND_REGISTRATION;
+import jdocs.cluster.TransformationMessages.TransformationJob;
+import jdocs.cluster.TransformationMessages.TransformationResult;
+import akka.actor.AbstractActor;
+import akka.cluster.Cluster;
+import akka.cluster.ClusterEvent.CurrentClusterState;
+import akka.cluster.ClusterEvent.MemberUp;
+import akka.cluster.Member;
+import akka.cluster.MemberStatus;
+
+//#backend
+public class TransformationBackend extends AbstractActor {
+
+  Cluster cluster = Cluster.get(getContext().getSystem());
+
+  //subscribe to cluster changes, MemberUp
+  @Override
+  public void preStart() {
+    cluster.subscribe(self(), MemberUp.class);
+  }
+
+  //re-subscribe when restart
+  @Override
+  public void postStop() {
+    cluster.unsubscribe(self());
+  }
+
+  @Override
+  public Receive createReceive() {
+    return receiveBuilder()
+      .match(TransformationJob.class, job -> {
+        getSender().tell(new TransformationResult(job.getText().toUpperCase()),
+         getSelf());
+      })
+      .match(CurrentClusterState.class, state -> {
+        for (Member member : state.getMembers()) {
+          if (member.status().equals(MemberStatus.up())) {
+            register(member);
+          }
+        }
+      })
+      .match(MemberUp.class, mUp -> {
+        register(mUp.member());
+      })
+      .build();
+  }
+
+  void register(Member member) {
+    if (member.hasRole("frontend"))
+      getContext().actorSelection(member.address() + "/user/frontend").tell(
+          BACKEND_REGISTRATION, getSelf());
+  }
+}
+//#backend