config.scala

// Provided by AmazingMongoFramework

case class MongoConfig(hostname: String, port: Int)

case class MongoConfigBuilder(hostname: Option[String] = Some("localhost"), port: Option[Int] = Some(27017)) {
  def withHostname(hostname: String) = copy(hostname = Some(hostname))
  def withPort(port: Int) = copy(port = Some(port))

  def build() = {
    // do some validation here..
    MongoConfig(hostname.get, port.get)
  }
}

class AmazingMongoFramework(config: MongoConfig)

// My application (example usage)
class MyApplication(config: Properties) {

  val framework = new AmazingMongoFramework(
    MongoConfigBuilder()
      .withHostname(config.getProperty("mongo.host"))
      .withPort(config.getProperty("mongo.port").toInt)
      .build())
}