Getting Started tutorial improvements (#23210)

akka-docs/src/test/java/jdocs/tutorial_3/inprogress2/DeviceInProgress2.java

@@ -0,0 +1,71 @@
+package jdocs.tutorial_3.inprogress2;
+
+//#device-with-read
+
+import java.util.Optional;
+
+import akka.actor.AbstractActor;
+import akka.actor.Props;
+import akka.event.Logging;
+import akka.event.LoggingAdapter;
+
+class Device extends AbstractActor {
+  private final LoggingAdapter log = Logging.getLogger(getContext().getSystem(), this);
+
+  final String groupId;
+
+  final String deviceId;
+
+  public Device(String groupId, String deviceId) {
+    this.groupId = groupId;
+    this.deviceId = deviceId;
+  }
+
+  public static Props props(String groupId, String deviceId) {
+    return Props.create(Device.class, groupId, deviceId);
+  }
+
+  //#read-protocol-2
+  public static final class ReadTemperature {
+    long requestId;
+
+    public ReadTemperature(long requestId) {
+      this.requestId = requestId;
+    }
+  }
+
+  public static final class RespondTemperature {
+    long requestId;
+    Optional<Double> value;
+
+    public RespondTemperature(long requestId, Optional<Double> value) {
+      this.requestId = requestId;
+      this.value = value;
+    }
+  }
+  //#read-protocol-2
+
+  Optional<Double> lastTemperatureReading = Optional.empty();
+
+  @Override
+  public void preStart() {
+    log.info("Device actor {}-{} started", groupId, deviceId);
+  }
+
+  @Override
+  public void postStop() {
+    log.info("Device actor {}-{} stopped", groupId, deviceId);
+  }
+
+  @Override
+  public Receive createReceive() {
+    return receiveBuilder()
+            .match(ReadTemperature.class, r -> {
+              getSender().tell(new RespondTemperature(r.requestId, lastTemperatureReading), getSelf());
+            })
+            .build();
+  }
+
+}
+
+//#device-with-read