#23 Create a utils class that will help users manage their properties

examples/src/main/resources/reference.conf

@@ -0,0 +1,18 @@
+{
+  topicName = "MyStandardTopic"
+
+  writer {
+    bootstrap.servers = "my.lab.kafka.cluster.com:9092"
+    key.serializer = "org.apache.kafka.common.serialization.StringSerializer"
+    value.serializer = "org.apache.kafka.common.serialization.StringSerializer"
+  }
+
+  reader {
+    bootstrap.servers = "my.lab.kafka.cluster.com:9092"
+    key.deserializer = "org.apache.kafka.common.serialization.StringDeserializer"
+    value.deserializer = "org.apache.kafka.common.serialization.StringDeserializer"
+    client.id = "DebugConsumer_007"
+    group.id = "DebugGroup_007"
+    auto.offset.reset = "earliest"
+  }
+}

examples/src/main/scala-2/za/co/absa/kafkacase/examples/reader/ReaderUsingsResourceHandling.scala

@@ -16,11 +16,11 @@
 
 package za.co.absa.kafkacase.examples.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
-import java.util.Properties
 
 object ReaderUsingsResourceHandling {
-  def apply[T: Decoder](readerProps: Properties, topicName: String): Unit = {
+  def apply[T: Decoder](readerConf: Config, topicName: String): Unit = {
     println("Scala 3 feature")
   }
 }

examples/src/main/scala-2/za/co/absa/kafkacase/examples/writer/WriterUsingsResourceHandling.scala

@@ -16,11 +16,11 @@
 
 package za.co.absa.kafkacase.examples.writer
 
+import com.typesafe.config.Config
 import io.circe.Encoder
-import java.util.Properties
 
 object WriterUsingsResourceHandling {
-  def apply[T: Encoder](writerProps: Properties, topicName: String, sampleMessageToWrite: T): Unit = {
+  def apply[T: Encoder](writerConf: Config, topicName: String, sampleMessageToWrite: T): Unit = {
     println("Scala 3 feature")
   }
 }

examples/src/main/scala-3/za/co/absa/kafkacase/examples/reader/ReaderUsingsResourceHandling.scala

@@ -19,12 +19,11 @@ package za.co.absa.kafkacase.examples.reader
 import io.circe.Decoder
 import za.co.absa.kafkacase.reader.ReaderImpl
 
-import java.util.Properties
 import scala.util.Using
 
 object ReaderUsingsResourceHandling {
-  def apply[T: Decoder](readerProps: Properties, topicName: String): Unit = {
-    Using(new ReaderImpl[T](readerProps, topicName, neverEnding = false)) { reader =>
+  def apply[T: Decoder](readerConf: Config, topicName: String): Unit = {
+    Using(new ReaderImpl[T](readerConf, topicName, neverEnding = false)) { reader =>
       for (item <- reader)
         println(item)
     }

examples/src/main/scala-3/za/co/absa/kafkacase/examples/writer/WriterUsingsResourceHandling.scala

@@ -19,12 +19,11 @@ package za.co.absa.kafkacase.examples.writer
 import io.circe.Encoder
 import za.co.absa.kafkacase.writer.WriterImpl
 
-import java.util.Properties
 import scala.util.Using
 
 object WriterUsingsResourceHandling {
-  def apply[T: Encoder](writerProps: Properties, topicName: String, sampleMessageToWrite: T): Unit = {
-    Using(new WriterImpl[T](writerProps, topicName)) { writer =>
+  def apply[T: Encoder](writerConf: Config, topicName: String, sampleMessageToWrite: T): Unit = {
+    Using(new WriterImpl[T](writerConf, topicName)) { writer =>
       writer.write("sampleMessageKey1", sampleMessageToWrite)
       writer.write("sampleMessageKey2", sampleMessageToWrite)
     }

examples/src/main/scala/za/co/absa/kafkacase/examples/KafkaCase.scala

@@ -16,15 +16,14 @@
 
 package za.co.absa.kafkacase.examples
 
-import org.apache.kafka.clients.consumer.ConsumerConfig
-import org.apache.kafka.clients.producer.ProducerConfig
+import com.typesafe.config.ConfigFactory
 import za.co.absa.kafkacase.examples.reader.{ReaderCustomResourceHandling, ReaderManualResourceHandling, ReaderReadOnce, ReaderUsingsResourceHandling}
 import za.co.absa.kafkacase.examples.writer.{WriterCustomResourceHandling, WriterManualResourceHandling, WriterUsingsResourceHandling, WriterWriteOnce}
 import za.co.absa.kafkacase.models.topics.EdlaChange
 
-import java.util.{Properties, UUID}
-
 object KafkaCase {
+  private val config = ConfigFactory.load()
+
   // This goes from your application logic
   private val sampleMessageToWrite = EdlaChange(
     app_id_snow = "N/A",
@@ -39,33 +38,25 @@ object KafkaCase {
     timestamp_event = 12345
   )
 
-  // This goes from your config / domain knowledge
-  private val topicName = "KillMePleaseTopic"
-
-  // This goes from your writer configs
-  private val writerProps = new Properties()
-  writerProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "ZADALNRAPP00009.corp.dsarena.com:9092")
-  writerProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer")
-  writerProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer")
-
-  // This goes from your reader configs
-  private val readerProps = new Properties()
-  readerProps.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "ZADALNRAPP00009.corp.dsarena.com:9092")
-  readerProps.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
-  readerProps.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringDeserializer")
-  readerProps.put(ConsumerConfig.CLIENT_ID_CONFIG, s"DebugConsumer_${UUID.randomUUID()}")
-  readerProps.put(ConsumerConfig.GROUP_ID_CONFIG, s"DebugGroup_${UUID.randomUUID()}")
-  readerProps.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest")
-
-
   def main(args: Array[String]): Unit = {
-    WriterManualResourceHandling(writerProps, topicName, sampleMessageToWrite)
-    WriterCustomResourceHandling(writerProps, topicName, sampleMessageToWrite)
-    WriterUsingsResourceHandling(writerProps, topicName, sampleMessageToWrite)
-    WriterWriteOnce(writerProps, topicName, sampleMessageToWrite)
-    ReaderManualResourceHandling[EdlaChange](readerProps, topicName)
-    ReaderCustomResourceHandling[EdlaChange](readerProps, topicName)
-    ReaderUsingsResourceHandling[EdlaChange](readerProps, topicName)
-    ReaderReadOnce[EdlaChange](readerProps, topicName)
+    val writerConfig = config.getConfig("writer")
+    val readerConfig = config.getConfig("reader")
+    val topicName = config.getString("topicName")
+    println("Sample how to use writer with manual resource handling")
+    WriterManualResourceHandling(writerConfig, topicName, sampleMessageToWrite)
+    println("Sample how to use writer with custom resource handling")
+    WriterCustomResourceHandling(writerConfig, topicName, sampleMessageToWrite)
+    println("Sample how to use writer with Usings in scala 3")
+    WriterUsingsResourceHandling(writerConfig, topicName, sampleMessageToWrite)
+    println("Sample how to use writer write-once fashion")
+    WriterWriteOnce(writerConfig, topicName, sampleMessageToWrite)
+    println("Sample how to use reader with manual resource handling")
+    ReaderManualResourceHandling[EdlaChange](readerConfig, topicName)
+    println("Sample how to use reader with custom resource handling")
+    ReaderCustomResourceHandling[EdlaChange](readerConfig, topicName)
+    println("Sample how to use reader with Usings in scala 3")
+    ReaderUsingsResourceHandling[EdlaChange](readerConfig, topicName)
+    println("Sample how to use reader read-once fashion")
+    ReaderReadOnce[EdlaChange](readerConfig, topicName)
   }
 }

examples/src/main/scala/za/co/absa/kafkacase/examples/reader/ReaderCustomResourceHandling.scala

@@ -16,15 +16,14 @@
 
 package za.co.absa.kafkacase.examples.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
 import za.co.absa.kafkacase.models.utils.ResourceHandler.withResource
 import za.co.absa.kafkacase.reader.ReaderImpl
 
-import java.util.Properties
-
 object ReaderCustomResourceHandling {
-  def apply[T: Decoder](readerProps: Properties, topicName: String): Unit = {
-    withResource(new ReaderImpl[T](readerProps, topicName, neverEnding = false))(reader => {
+  def apply[T: Decoder](readerConf: Config, topicName: String): Unit = {
+    withResource(ReaderImpl[T](readerConf, topicName))(reader => {
       for (item <- reader)
         println(item)
     })

examples/src/main/scala/za/co/absa/kafkacase/examples/reader/ReaderManualResourceHandling.scala

@@ -16,14 +16,13 @@
 
 package za.co.absa.kafkacase.examples.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
 import za.co.absa.kafkacase.reader.ReaderImpl
 
-import java.util.Properties
-
 object ReaderManualResourceHandling {
-  def apply[T: Decoder](readerProps: Properties, topicName: String): Unit = {
-    val reader = new ReaderImpl[T](readerProps, topicName, neverEnding = false)
+  def apply[T: Decoder](readerConf: Config, topicName: String): Unit = {
+    val reader = ReaderImpl[T](readerConf, topicName)
     try {
       for (item <- reader)
         println(item)

examples/src/main/scala/za/co/absa/kafkacase/examples/reader/ReaderReadOnce.scala

@@ -16,12 +16,11 @@
 
 package za.co.absa.kafkacase.examples.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
 import za.co.absa.kafkacase.reader.Reader
 
-import java.util.Properties
-
 object ReaderReadOnce {
-  def apply[T: Decoder](readerProps: Properties, topicName: String): Unit =
-    Reader.readOnce[T](readerProps, topicName, println)
+  def apply[T: Decoder](readerConf: Config, topicName: String): Unit =
+    Reader.readOnce[T](readerConf, topicName, (item: (String, Either[String, T])) => println(item))
 }

examples/src/main/scala/za/co/absa/kafkacase/examples/writer/WriterCustomResourceHandling.scala

@@ -16,15 +16,16 @@
 
 package za.co.absa.kafkacase.examples.writer
 
+import com.typesafe.config.Config
 import io.circe.Encoder
 import za.co.absa.kafkacase.models.utils.ResourceHandler.withResource
 import za.co.absa.kafkacase.writer.WriterImpl
 
 import java.util.Properties
 
 object WriterCustomResourceHandling {
-  def apply[T: Encoder](writerProps: Properties, topicName: String, sampleMessageToWrite: T): Unit = {
-    withResource(new WriterImpl[T](writerProps, topicName))(writer => {
+  def apply[T: Encoder](writerConf: Config, topicName: String, sampleMessageToWrite: T): Unit = {
+    withResource(new WriterImpl[T](writerConf, topicName))(writer => {
       writer.write("sampleMessageKey1", sampleMessageToWrite)
       writer.write("sampleMessageKey2", sampleMessageToWrite)
     })

examples/src/main/scala/za/co/absa/kafkacase/examples/writer/WriterManualResourceHandling.scala

@@ -16,14 +16,13 @@
 
 package za.co.absa.kafkacase.examples.writer
 
+import com.typesafe.config.Config
 import io.circe.Encoder
 import za.co.absa.kafkacase.writer.WriterImpl
 
-import java.util.Properties
-
 object WriterManualResourceHandling {
-  def apply[T: Encoder](writerProps: Properties, topicName: String, sampleMessageToWrite: T): Unit = {
-    val writer = new WriterImpl[T](writerProps, topicName)
+  def apply[T: Encoder](writerConf: Config, topicName: String, sampleMessageToWrite: T): Unit = {
+    val writer = new WriterImpl[T](writerConf, topicName)
     try {
       writer.write("sampleMessageKey1", sampleMessageToWrite)
       writer.write("sampleMessageKey2", sampleMessageToWrite)

examples/src/main/scala/za/co/absa/kafkacase/examples/writer/WriterWriteOnce.scala

@@ -16,12 +16,11 @@
 
 package za.co.absa.kafkacase.examples.writer
 
+import com.typesafe.config.Config
 import io.circe.Encoder
 import za.co.absa.kafkacase.writer.Writer
 
-import java.util.Properties
-
 object WriterWriteOnce {
-  def apply[T: Encoder](writerProps: Properties, topicName: String, sampleMessageToWrite: T): Unit =
-    Writer.writeOnce(writerProps, topicName, "sampleKey", sampleMessageToWrite)
+  def apply[T: Encoder](writerConf: Config, topicName: String, sampleMessageToWrite: T): Unit =
+    Writer.writeOnce(writerConf, topicName, "sampleKey", sampleMessageToWrite)
 }

project/Dependencies.scala

@@ -13,12 +13,14 @@ object Dependencies {
 
   def readerDependencies: Seq[ModuleID] = Seq(
     "io.circe" %% "circe-parser" % "0.14.9",
-    "org.apache.kafka" % "kafka-clients" % "3.8.0"
+    "org.apache.kafka" % "kafka-clients" % "3.8.0",
+    "com.typesafe" % "config" % "1.4.3"
   )
 
   def writerDependencies: Seq[ModuleID] = Seq(
     "io.circe" %% "circe-parser" % "0.14.9",
-    "org.apache.kafka" % "kafka-clients" % "3.8.0"
+    "org.apache.kafka" % "kafka-clients" % "3.8.0",
+    "com.typesafe" % "config" % "1.4.3"
   )
 
   def examplesDependencies: Seq[ModuleID] = Seq.empty[ModuleID]

reader/src/main/scala/za/co/absa/kafkacase/reader/Reader.scala

@@ -16,6 +16,7 @@
 
 package za.co.absa.kafkacase.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
 
 import java.util.Properties
@@ -24,7 +25,17 @@ trait Reader[TType] extends Iterator[(String, Either[String, TType])] with AutoC
 
 object Reader {
   def readOnce[T: Decoder](readerProps: Properties, topicName: String, work: ((String, Either[String, T])) => Unit): Unit = {
-    val reader = new ReaderImpl[T](readerProps, topicName, neverEnding = false)
+    val reader = ReaderImpl[T](readerProps, topicName)
+    try {
+      for (item <- reader)
+        work(item)
+    } finally {
+      reader.close()
+    }
+  }
+
+  def readOnce[T: Decoder](readerConf: Config, topicName: String, work: ((String, Either[String, T])) => Unit): Unit = {
+    val reader = ReaderImpl[T](readerConf, topicName)
     try {
       for (item <- reader)
         work(item)

reader/src/main/scala/za/co/absa/kafkacase/reader/ReaderImpl.scala

@@ -16,17 +16,18 @@
 
 package za.co.absa.kafkacase.reader
 
+import com.typesafe.config.Config
 import io.circe.Decoder
 import io.circe.jawn.decode
 import org.slf4j.LoggerFactory
 import org.apache.kafka.clients.consumer.{ConsumerRecord, KafkaConsumer}
-import za.co.absa.kafkacase.reader.ReaderImpl.{DEFAULT_TIMEOUT, log}
+import za.co.absa.kafkacase.reader.ReaderImpl.{DEFAULT_TIMEOUT, convertConfigToProperties, log}
 
 import java.time.Duration
 import java.util
 import java.util.Properties
 
-class ReaderImpl[TType: Decoder](props: Properties, topic: String, timeout: Duration = DEFAULT_TIMEOUT, neverEnding: Boolean = true) extends Reader[TType] {
+class ReaderImpl[TType: Decoder](props: Properties, topic: String, timeout: Duration, neverEnding: Boolean) extends Reader[TType] {
   private val consumer = new KafkaConsumer[String, String](props)
   consumer.subscribe(util.Arrays.asList(topic))
   private var singlePollIterator = fetchNextBatch()
@@ -60,5 +61,41 @@ class ReaderImpl[TType: Decoder](props: Properties, topic: String, timeout: Dura
 
 object ReaderImpl {
   private val DEFAULT_TIMEOUT: Duration = Duration.ofSeconds(3)
+  private val DEFAULT_NEVER_ENDING: Boolean = true
   private val log = LoggerFactory.getLogger(this.getClass)
+
+  // note: scala can't handle default parameters together with overloading.... hence slightly exponential number of auxiliary apply methods
+  // Primary method that contains default arguments
+  def apply[TType: Decoder](props: Properties, topic: String, timeout: Duration = DEFAULT_TIMEOUT, neverEnding: Boolean = DEFAULT_NEVER_ENDING): ReaderImpl[TType] = {
+    new ReaderImpl[TType](props, topic, timeout, neverEnding)
+  }
+
+  // Overloaded method with Config and all optional arguments
+  def apply[TType: Decoder](config: Config, topic: String, timeout: Duration, neverEnding: Boolean): ReaderImpl[TType] = {
+    val props = convertConfigToProperties(config)
+    apply[TType](props, topic, timeout, neverEnding)
+  }
+
+  // Overloaded method with Config and neverEnding optional argument
+  def apply[TType: Decoder](config: Config, topic: String, neverEnding: Boolean): ReaderImpl[TType] = {
+    apply[TType](config, topic, DEFAULT_TIMEOUT, neverEnding)
+  }
+
+  // Overloaded method with Config and timeout optional argument
+  def apply[TType: Decoder](config: Config, topic: String, timeout: Duration): ReaderImpl[TType] = {
+    apply[TType](config, topic, timeout, DEFAULT_NEVER_ENDING)
+  }
+
+  // Overloaded method with Config and none of optional arguments
+  def apply[TType: Decoder](config: Config, topic: String): ReaderImpl[TType] = {
+    apply[TType](config, topic, DEFAULT_TIMEOUT, DEFAULT_NEVER_ENDING)
+  }
+
+  private def convertConfigToProperties(config: Config): Properties = {
+    val properties = new Properties()
+    config.entrySet().forEach { entry =>
+      properties.put(entry.getKey, config.getString(entry.getKey))
+    }
+    properties
+  }
 }

writer/src/main/scala/za/co/absa/kafkacase/writer/Writer.scala

@@ -16,6 +16,7 @@
 
 package za.co.absa.kafkacase.writer
 
+import com.typesafe.config.Config
 import io.circe.Encoder
 
 import java.util.Properties
@@ -39,4 +40,13 @@ object Writer {
       writer.close()
     }
   }
+
+  def writeOnce[T: Encoder](writerConf: Config, topicName: String, messageKey: String, sampleMessageToWrite: T): Unit = {
+    val writer = new WriterImpl[T](writerConf, topicName)
+    try {
+      writer.write(messageKey, sampleMessageToWrite)
+    } finally {
+      writer.close()
+    }
+  }
 }