Reading, Processing and Writing... sounds batch

	package batch
	import scala.xml.Elem
	trait ItemReader[A] {
	def read: Option[A]
	def hasNext: Boolean
	}
	trait ItemProcessor[A,B] {
	def process(x: A): B
	}
	trait ItemWriter[B] {
	def write(items: List[B]): Unit
	}
	trait BatchProcessor[S,T] {
	val itemReader: ItemReader[S]
	val itemProcessor: ItemProcessor[S,T]
	val itemWriter: ItemWriter[T]
	def execute: Unit = {
	while(itemReader.hasNext) {
	for (item <- itemReader.read){
	itemWriter.write(List(itemProcessor.process(item)))
	}
	}
	}
	}
	class ListReader[A](list: List[A]) extends ItemReader[A] {
	val iterator:Iterator[A] = list.iterator
	override def read: Option[A] = {
	new Some(iterator.next)
	}
	override def hasNext: Boolean = {
	iterator.hasNext
	}
	}
	/**
	* Our simple batchprogram will
	* - read cities one by one from a list of cities
	* - process them (transform from scala to xml)
	* - write each list containing 1 city to the console
	*
	* I left out chunking for simplicity
	*/
	object BatchProgram {
	case class City(name: String, population: Long) {
	def marshal: Elem = {
	<city>
	<name>{name}</name>
	<population>{population}</population>
	</city>
	}
	}
	val cities = List(City("Paris", 2234000000L), City("London", 8174000000L))
	val cityReader: ListReader[City] = new ListReader(cities)
	val cityProcessor:ItemProcessor[City,Elem] = new ItemProcessor[City,Elem]() {
	override def process(city: City): Elem = {
	city.marshal
	}
	}
	val cityWriter: ItemWriter[Elem] = new ItemWriter[Elem]() {
	override def write(items: List[Elem]): Unit = {
	println("*****************BATCH START*************")
	for (item <- items) println(item)
	println("*****************BATCH END***************")
	}
	}
	val batchProcessor: BatchProcessor[City, Elem] = new {
	val itemReader = cityReader
	val itemProcessor = cityProcessor
	val itemWriter = cityWriter
	} with BatchProcessor[City, Elem]
	def main(args: Array[String]) {
	batchProcessor.execute
	}
	}
	/**
	This will print the following to the console:
	*****************BATCH START*************
	<city>
	<name>Paris</name>
	<population>2234000000</population>
	</city>
	*****************BATCH END***************
	*****************BATCH START*************
	<city>
	<name>London</name>
	<population>8174000000</population>
	</city>
	*****************BATCH END***************
	**/

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