+per #16541 java docs for persistence query

akka-docs/rst/java/code/docs/persistence/PersistenceQueryDocTest.java

@@ -0,0 +1,75 @@
+/**
+ * Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package docs.persistence;
+
+import akka.actor.*;
+import akka.event.EventStreamSpec;
+import akka.japi.Function;
+import akka.japi.Procedure;
+import akka.pattern.BackoffSupervisor;
+import akka.persistence.*;
+import akka.persistence.query.*;
+import akka.persistence.query.javadsl.ReadJournal;
+import akka.stream.javadsl.Source;
+import akka.util.Timeout;
+import docs.persistence.query.MyEventsByTagPublisher;
+import scala.collection.Seq;
+import scala.concurrent.duration.Duration;
+import scala.concurrent.duration.FiniteDuration;
+import scala.runtime.BoxedUnit;
+
+import java.io.Serializable;
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+
+public class PersistenceQueryDocTest {
+
+  final Timeout timeout = Timeout.durationToTimeout(FiniteDuration.create(3, TimeUnit.SECONDS));
+
+  //#my-read-journal
+    class MyReadJournal implements ReadJournal {
+      private final ExtendedActorSystem system;
+
+    public MyReadJournal(ExtendedActorSystem system) {
+      this.system = system;
+    }
+
+      final FiniteDuration defaultRefreshInterval = FiniteDuration.create(3, TimeUnit.SECONDS);
+
+      @SuppressWarnings("unchecked")
+      public <T, M> Source<T, M> query(Query<T, M> q, Hint... hints) {
+        if (q instanceof EventsByTag) {
+          final EventsByTag eventsByTag = (EventsByTag) q;
+          final String tag = eventsByTag.tag();
+          long offset = eventsByTag.offset();
+
+          final Props props = MyEventsByTagPublisher.props(tag, offset, refreshInterval(hints));
+
+          return (Source<T, M>) Source.<EventEnvelope>actorPublisher(props)
+                       .mapMaterializedValue(noMaterializedValue());
+        } else {
+          // unsuported
+            return Source.<T>failed(
+              new UnsupportedOperationException(
+                "Query $unsupported not supported by " + getClass().getName()))
+              .mapMaterializedValue(noMaterializedValue());
+        }
+      }
+
+      private FiniteDuration refreshInterval(Hint[] hints) {
+        FiniteDuration ret = defaultRefreshInterval;
+        for (Hint hint : hints)
+          if (hint instanceof RefreshInterval)
+            ret = ((RefreshInterval) hint).interval();
+        return ret;
+      }
+
+        private <I, M> akka.japi.function.Function<I, M> noMaterializedValue () {
+          return param -> (M) null;
+        }
+
+  }
+    //#my-read-journal
+}