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The following commit(s) were added to refs/heads/main by this push:
new 0e6b505 refactor: replace deprecated `extends App` with explicit main
method (#178)
0e6b505 is described below
commit 0e6b5055d1540c49cd8b55ebb049fd71c7d4ff0a
Author: He-Pin(kerr) <[email protected]>
AuthorDate: Mon Jul 6 16:24:18 2026 +0800
refactor: replace deprecated `extends App` with explicit main method (#178)
Motivation:
`extends App` is deprecated in Scala 3. Replace with explicit `def main`
method for forward compatibility.
Modification:
Replace `object X extends App { ... }` with
`object X { def main(args: Array[String]): Unit = { ... } }`
in 5 sample application files.
Result:
No more usage of deprecated `scala.App` trait. Code is compatible with
Scala 3.
Tests:
Not run - docs only
References:
None - Scala 3 compatibility
---
.../src/main/scala/com/example/ClusteringApp.scala | 10 +--
.../pekko/sample/cluster/kubernetes/DemoApp.scala | 38 ++++++-----
.../client/src/main/scala/client/ClientApp.scala | 36 +++++-----
.../sharding/embeddedkafka/KafkaBroker.scala | 24 ++++---
.../kafka/producer/UserEventProducer.scala | 78 +++++++++++-----------
5 files changed, 98 insertions(+), 88 deletions(-)
diff --git
a/pekko-sample-cluster-docker-compose-scala/src/main/scala/com/example/ClusteringApp.scala
b/pekko-sample-cluster-docker-compose-scala/src/main/scala/com/example/ClusteringApp.scala
index 915d382..ab91685 100644
---
a/pekko-sample-cluster-docker-compose-scala/src/main/scala/com/example/ClusteringApp.scala
+++
b/pekko-sample-cluster-docker-compose-scala/src/main/scala/com/example/ClusteringApp.scala
@@ -3,9 +3,11 @@ package com.example
import org.apache.pekko.actor.typed.ActorSystem
import com.typesafe.config.ConfigFactory
-object ClusteringApp extends App {
- val config = ConfigFactory.load()
- val clusterName = config.getString("clustering.cluster.name")
+object ClusteringApp {
+ def main(args: Array[String]): Unit = {
+ val config = ConfigFactory.load()
+ val clusterName = config.getString("clustering.cluster.name")
- ActorSystem(ClusterListener(), clusterName)
+ ActorSystem(ClusterListener(), clusterName)
+ }
}
diff --git
a/pekko-sample-cluster-kubernetes-scala/src/main/scala/pekko/sample/cluster/kubernetes/DemoApp.scala
b/pekko-sample-cluster-kubernetes-scala/src/main/scala/pekko/sample/cluster/kubernetes/DemoApp.scala
index 928209c..bae234d 100644
---
a/pekko-sample-cluster-kubernetes-scala/src/main/scala/pekko/sample/cluster/kubernetes/DemoApp.scala
+++
b/pekko-sample-cluster-kubernetes-scala/src/main/scala/pekko/sample/cluster/kubernetes/DemoApp.scala
@@ -12,28 +12,30 @@ import org.apache.pekko.{ actor => classic }
import scala.concurrent.ExecutionContext
-object DemoApp extends App {
+object DemoApp {
+ def main(args: Array[String]): Unit = {
- ActorSystem[Nothing](Behaviors.setup[Nothing] { context =>
- import org.apache.pekko.actor.typed.scaladsl.adapter._
- implicit val classicSystem: classic.ActorSystem =
context.system.toClassic
- implicit val ec: ExecutionContext = context.system.executionContext
+ ActorSystem[Nothing](Behaviors.setup[Nothing] { context =>
+ import org.apache.pekko.actor.typed.scaladsl.adapter._
+ implicit val classicSystem: classic.ActorSystem =
context.system.toClassic
+ implicit val ec: ExecutionContext = context.system.executionContext
- val cluster = Cluster(context.system)
- context.log.info("Started [" + context.system + "], cluster.selfAddress
= " + cluster.selfMember.address + ")")
+ val cluster = Cluster(context.system)
+ context.log.info("Started [" + context.system + "],
cluster.selfAddress = " + cluster.selfMember.address + ")")
- Http().newServerAt("0.0.0.0", 8080).bind(complete("Hello world"))
+ Http().newServerAt("0.0.0.0", 8080).bind(complete("Hello world"))
- // Create an actor that handles cluster domain events
- val listener =
context.spawn(Behaviors.receive[ClusterEvent.MemberEvent]((ctx, event) => {
- ctx.log.info("MemberEvent: {}", event)
- Behaviors.same
- }), "listener")
+ // Create an actor that handles cluster domain events
+ val listener =
context.spawn(Behaviors.receive[ClusterEvent.MemberEvent]((ctx, event) => {
+ ctx.log.info("MemberEvent: {}", event)
+ Behaviors.same
+ }), "listener")
- Cluster(context.system).subscriptions ! Subscribe(listener,
classOf[ClusterEvent.MemberEvent])
+ Cluster(context.system).subscriptions ! Subscribe(listener,
classOf[ClusterEvent.MemberEvent])
- PekkoManagement.get(classicSystem).start()
- ClusterBootstrap.get(classicSystem).start()
- Behaviors.empty
- }, "appka")
+ PekkoManagement.get(classicSystem).start()
+ ClusterBootstrap.get(classicSystem).start()
+ Behaviors.empty
+ }, "appka")
+ }
}
diff --git
a/pekko-sample-kafka-to-sharding-scala/client/src/main/scala/client/ClientApp.scala
b/pekko-sample-kafka-to-sharding-scala/client/src/main/scala/client/ClientApp.scala
index 8049506..2b99b26 100644
---
a/pekko-sample-kafka-to-sharding-scala/client/src/main/scala/client/ClientApp.scala
+++
b/pekko-sample-kafka-to-sharding-scala/client/src/main/scala/client/ClientApp.scala
@@ -11,24 +11,26 @@ import scala.concurrent.ExecutionContextExecutor
import scala.concurrent.duration.Duration
import scala.io.StdIn
-object ClientApp extends App {
- implicit val system: ActorSystem = ActorSystem("UserClient")
- implicit val mat: Materializer = Materializer.createMaterializer(system)
- implicit val ec: ExecutionContextExecutor = system.dispatcher
- val clientSettings = GrpcClientSettings.connectToServiceAt("127.0.0.1",
8081).withTls(false)
- val client = UserServiceClient(clientSettings)
+object ClientApp {
+ def main(args: Array[String]): Unit = {
+ implicit val system: ActorSystem = ActorSystem("UserClient")
+ implicit val mat: Materializer = Materializer.createMaterializer(system)
+ implicit val ec: ExecutionContextExecutor = system.dispatcher
+ val clientSettings = GrpcClientSettings.connectToServiceAt("127.0.0.1",
8081).withTls(false)
+ val client = UserServiceClient(clientSettings)
- var userId = ""
- while (userId != ":q") {
- println("Enter user id or :q to quit")
- userId = StdIn.readLine()
- if (userId != ":q") {
- val runningTotal =
Await.result(client.userStats(UserStatsRequest(userId)), Duration.Inf)
- println(
- s"User ${userId} has made ${runningTotal.totalPurchases} purchases for
a total of ${runningTotal.amountSpent}p")
- }
+ var userId = ""
+ while (userId != ":q") {
+ println("Enter user id or :q to quit")
+ userId = StdIn.readLine()
+ if (userId != ":q") {
+ val runningTotal =
Await.result(client.userStats(UserStatsRequest(userId)), Duration.Inf)
+ println(
+ s"User ${userId} has made ${runningTotal.totalPurchases} purchases
for a total of ${runningTotal.amountSpent}p")
+ }
+ }
+ println("Exiting")
+ system.terminate()
}
- println("Exiting")
- system.terminate()
}
diff --git
a/pekko-sample-kafka-to-sharding-scala/kafka/src/main/scala/sample/sharding/embeddedkafka/KafkaBroker.scala
b/pekko-sample-kafka-to-sharding-scala/kafka/src/main/scala/sample/sharding/embeddedkafka/KafkaBroker.scala
index f1eb3b9..0753d19 100644
---
a/pekko-sample-kafka-to-sharding-scala/kafka/src/main/scala/sample/sharding/embeddedkafka/KafkaBroker.scala
+++
b/pekko-sample-kafka-to-sharding-scala/kafka/src/main/scala/sample/sharding/embeddedkafka/KafkaBroker.scala
@@ -3,20 +3,22 @@ package sample.sharding.embeddedkafka
import net.manub.embeddedkafka.{ EmbeddedKafka, EmbeddedKafkaConfig }
import org.slf4j.LoggerFactory
-object KafkaBroker extends App with EmbeddedKafka {
- val log = LoggerFactory.getLogger(this.getClass)
+object KafkaBroker extends EmbeddedKafka {
+ def main(args: Array[String]): Unit = {
+ val log = LoggerFactory.getLogger(this.getClass)
- val port = 9092
- val topic = "user-events"
- val partitions = 128
+ val port = 9092
+ val topic = "user-events"
+ val partitions = 128
- implicit val config: EmbeddedKafkaConfig = EmbeddedKafkaConfig(kafkaPort =
port)
- val server = EmbeddedKafka.start()
+ implicit val config: EmbeddedKafkaConfig = EmbeddedKafkaConfig(kafkaPort =
port)
+ val server = EmbeddedKafka.start()
- createCustomTopic(topic = topic, partitions = partitions)
+ createCustomTopic(topic = topic, partitions = partitions)
- log.info(s"Kafka running: localhost:$port")
- log.info(s"Topic '$topic' with $partitions partitions created")
+ log.info(s"Kafka running: localhost:$port")
+ log.info(s"Topic '$topic' with $partitions partitions created")
- server.broker.awaitShutdown()
+ server.broker.awaitShutdown()
+ }
}
diff --git
a/pekko-sample-kafka-to-sharding-scala/producer/src/main/scala/sharding/kafka/producer/UserEventProducer.scala
b/pekko-sample-kafka-to-sharding-scala/producer/src/main/scala/sharding/kafka/producer/UserEventProducer.scala
index 74621c4..f8a32a4 100644
---
a/pekko-sample-kafka-to-sharding-scala/producer/src/main/scala/sharding/kafka/producer/UserEventProducer.scala
+++
b/pekko-sample-kafka-to-sharding-scala/producer/src/main/scala/sharding/kafka/producer/UserEventProducer.scala
@@ -15,42 +15,44 @@ import scala.concurrent.Future
import scala.concurrent.duration._
import scala.util.Random
-object UserEventProducer extends App {
-
- implicit val system: ActorSystem = ActorSystem(
- "UserEventProducer",
- ConfigFactory.parseString("""
- pekko.actor.provider = "local"
- """.stripMargin).withFallback(ConfigFactory.load()).resolve())
-
- val log = Logging(system, "UserEventProducer")
-
- val config = system.settings.config.getConfig("pekko.kafka.producer")
-
- val producerConfig =
ProducerConfig(system.settings.config.getConfig("kafka-to-sharding-producer"))
-
- val producerSettings: ProducerSettings[String, Array[Byte]] =
- ProducerSettings(config, new StringSerializer, new ByteArraySerializer)
- .withBootstrapServers(producerConfig.bootstrapServers)
-
- val nrUsers = 200
- val maxPrice = 10000
- val maxQuantity = 5
- val products = List("cat t-shirt", "pekko t-shirt", "skis", "climbing
shoes", "rope")
-
- val done: Future[Done] =
- Source
- .tick(1.second, 1.second, "tick")
- .map(_ => {
- val randomEntityId = Random.nextInt(nrUsers).toString
- val price = Random.nextInt(maxPrice)
- val quantity = Random.nextInt(maxQuantity)
- val product = products(Random.nextInt(products.size))
- val message = UserPurchaseProto(randomEntityId, product, quantity,
price).toByteArray
- log.info("Sending message to user {}", randomEntityId)
- // rely on the default kafka partitioner to hash the key and
distribute among shards
- // the logic of the default partitioner must be replicated in
MessageExtractor entityId -> shardId function
- new ProducerRecord[String, Array[Byte]](producerConfig.topic,
randomEntityId, message)
- })
- .runWith(Producer.plainSink(producerSettings))
+object UserEventProducer {
+ def main(args: Array[String]): Unit = {
+
+ implicit val system: ActorSystem = ActorSystem(
+ "UserEventProducer",
+ ConfigFactory.parseString("""
+ pekko.actor.provider = "local"
+ """.stripMargin).withFallback(ConfigFactory.load()).resolve())
+
+ val log = Logging(system, "UserEventProducer")
+
+ val config = system.settings.config.getConfig("pekko.kafka.producer")
+
+ val producerConfig =
ProducerConfig(system.settings.config.getConfig("kafka-to-sharding-producer"))
+
+ val producerSettings: ProducerSettings[String, Array[Byte]] =
+ ProducerSettings(config, new StringSerializer, new ByteArraySerializer)
+ .withBootstrapServers(producerConfig.bootstrapServers)
+
+ val nrUsers = 200
+ val maxPrice = 10000
+ val maxQuantity = 5
+ val products = List("cat t-shirt", "pekko t-shirt", "skis", "climbing
shoes", "rope")
+
+ val done: Future[Done] =
+ Source
+ .tick(1.second, 1.second, "tick")
+ .map(_ => {
+ val randomEntityId = Random.nextInt(nrUsers).toString
+ val price = Random.nextInt(maxPrice)
+ val quantity = Random.nextInt(maxQuantity)
+ val product = products(Random.nextInt(products.size))
+ val message = UserPurchaseProto(randomEntityId, product, quantity,
price).toByteArray
+ log.info("Sending message to user {}", randomEntityId)
+ // rely on the default kafka partitioner to hash the key and
distribute among shards
+ // the logic of the default partitioner must be replicated in
MessageExtractor entityId -> shardId function
+ new ProducerRecord[String, Array[Byte]](producerConfig.topic,
randomEntityId, message)
+ })
+ .runWith(Producer.plainSink(producerSettings))
+ }
}
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