run command line program within play 2.0 environment

CommandRunner.scala

package commands

import scala.sys._
import play.api._
import java.io.File

/**
 * Run command in play environment.
 *
 * Assume, that we have in play 'app' directory subdirectory 'commands'
 * and in commands we have 'commands implementations' : scala objects or java
 * classes with run(args:String*) method. Also Assume, that this implementation
 * use play configuration, plugins api, etc ... - i. e. must run in play environment.
 *
 *This runner accept calls like CommandRunner.run("cmd",args), determinate implementation
 *for "cmd" (i.e. object or class "commands.Cmd") and call run method of found implementation
 *in play application environment (initializing one if needed) 
 */
object CommandRunner
{

  def insideApp[A](f: =>A):A =
  {
   if (Play.maybeApplication.isEmpty) {
       val app = new Application(new File("."),this.getClass.getClassLoader, None, Mode.Test);
       Play.start(app);
       //  play.stop will be called on jvm shutdown. Does not call one,
       //  immediatly after f, becouse we want to call command multiple times 
       //  from sbt console.
       try {
           Runtime.getRuntime.addShutdownHook(ShutdownHookThread{ Play.stop() });
       } catch {
           case ex: IllegalArgumentException =>
                // this hook was already registered (?) - may-be, skipping.
       }
   }
   f;
  }

  def run(cmdname:String, args: String*):Unit =
  {
    val cmd = findCommandObject(cmdname);
    try {
      insideApp {
         cmd.asInstanceOf[{ def run(args:String*):Unit }].run(args:_*)
      }
    } catch {
      case ex: ClassCastException =>
         throw new IllegalArgumentException(cmd.getClass.getName+" is not command: it does not define run");
    }
  }

  def findCommandObject(cmdname:String):AnyRef =
  {
   if (cmdname.length==0) {
     throw new IllegalArgumentException("invalid empty name for command");
   }
   try {
     val candidateClassName = "commands"+"."+upcase(cmdname)+"$";
     val candidateClass = Class.forName(candidateClassName);
     val singletonField = candidateClass.getField("MODULE$");
     singletonField.get(null);
   }catch{
     case ex: ClassNotFoundException => findJavaCommandClass(cmdname);
     case ex: NoSuchFieldException =>  throw new IllegalArgumentException(cmdname+" is not a scala object ");
   }
  }

  def findJavaCommandClass(cmdname:String):AnyRef =
  try {
     val candidateClassName = "commands"+"."+upcase(cmdname);
     val candidateClass = Class.forName(candidateClassName);
     candidateClass.newInstance().asInstanceOf[AnyRef]
  } catch {
     case ex: ClassNotFoundException => throw new IllegalStateException("Can't find class or object for command "+cmdname);
  }

  def upcase(s:String):String = s.patch(0,Seq(s.charAt(0).toUpper),1);

}