AOPを使わなくても処理の始まりと終わりにログを出力するtrait

gistfile1.scala

import scala.util.DynamicVariable
import scala.collection.immutable
import grizzled.slf4j.Logging

trait LoggingEx extends Logging {

  private val msgs = new DynamicVariable[Seq[String]](immutable.Queue.empty)

  private def withScope[T](msg: String, logger: (=> Any, => Throwable) => Unit, f: => T): T = {
    val newMsgs = msgs.value :+ msg
    val str = newMsgs.mkString(" : ")
    logger("%s : start".format(str), null)
    val r = msgs.withValue(newMsgs) {
      f
    }
    logger("%s : end".format(str), null)
    r
  }

  private def scoped[T](msg: String, logger: (=> Any, => Throwable) => Unit) {
    val newMsgs = msgs.value :+ msg
    val str = newMsgs.mkString(" : ")
    logger(str, null)
  }

  def withInfoScope[T](msg: String)(f: => T): T = if (isInfoEnabled) withScope(msg, info _, f) else f

  def withWarnScope[T](msg: String)(f: => T): T = if (isWarnEnabled) withScope(msg, warn _, f) else f

  def withErrorScope[T](msg: String)(f: => T): T = if (isErrorEnabled) withScope(msg, error _, f) else f

  def withDebugScope[T](msg: String)(f: => T): T = if (isDebugEnabled) withScope(msg, debug _, f) else f

  def scopedInfo(msg: String) {
    if (isInfoEnabled) scoped(msg, info _)
  }

  def scopedWarn(msg: String) {
    if (isWarnEnabled) scoped(msg, warn _)
  }

  def scopedError(msg: String) {
    if (isErrorEnabled) scoped(msg, error _)
  }

  def scopedDebug(msg: String) {
    if (isDebugEnabled) scoped(msg, debug _)
  }

}

// --

def printWord(msg:String):String = withDebugScope("printWord"){ // printWord : start
  scopedDebug("msg = " + msg) // printWord : msg = XXX
  println(msg)
  msg
} // printWord : end