Play Framework/Scala example source code file (Action.scala)

This example Play Framework source code file (Action.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Play Framework (and Scala) source code examples by using tags.

All credit for the original source code belongs to Play Framework; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Play Framework tags/keywords

a, action, actionfunction, api, bodyparser, concurrent, either, executioncontext, future, lib, library, p, play, play framework, r, requestheader

The Action.scala Play Framework example source code

/*
 * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
 */
package play.api.mvc

import play.api.libs.iteratee._
import play.api._
import play.core.Router.{ HandlerInvoker, HandlerInvokerFactory }
import scala.concurrent._
import scala.language.higherKinds

/**
 * An Handler handles a request. Play understands several types of handlers,
 * for example `EssentialAction`s and `WebSocket`s.
 *
 * The `Handler` used to handle the request is controlled by `GlobalSetting`s's
 * `onRequestReceived` method. The default implementation of
 * `onRequestReceived` delegates to `onRouteRequest` which calls the default
 * `Router`.
 */
trait Handler

/**
 * A handler that is able to tag requests. Usually mixed in to other handlers.
 */
trait RequestTaggingHandler extends Handler {
  def tagRequest(request: RequestHeader): RequestHeader
}

/**
 * Reference to a Handler, useful for contructing handlers from Java code.
 */
class HandlerRef[T](call: => T, handlerDef: play.core.Router.HandlerDef)(implicit hif: play.core.Router.HandlerInvokerFactory[T]) extends play.mvc.HandlerRef {

  lazy val invoker: HandlerInvoker[T] = hif.createInvoker(call, handlerDef)

  /**
   * Retrieve a real handler behind this ref.
   */
  def handler: play.api.mvc.Handler = {
    invoker.call(call)
  }

  /**
   * String representation of this Handler.
   */
  lazy val sym = {
    handlerDef.controller + "." + handlerDef.method + "(" + handlerDef.parameterTypes.map(_.getName).mkString(", ") + ")"
  }

  override def toString = {
    "HandlerRef[" + sym + ")]"
  }

}

/**
 * An `EssentialAction` underlies every `Action`. Given a `RequestHeader`, an
 * `EssentialAction` consumes the request body (an `Array[Byte]`) and returns
 * a `Result`.
 *
 * An `EssentialAction` is a `Handler`, which means it is one of the objects
 * that Play uses to handle requests.
 */
trait EssentialAction extends (RequestHeader => Iteratee[Array[Byte], Result]) with Handler {

  /**
   * Returns itself, for better support in the routes file.
   *
   * @return itself
   */
  def apply() = this

}

/**
 * Helper for creating `EssentialAction`s.
 */
object EssentialAction {

  def apply(f: RequestHeader => Iteratee[Array[Byte], Result]): EssentialAction = new EssentialAction {
    def apply(rh: RequestHeader) = f(rh)
  }
}

/**
 * An action is essentially a (Request[A] => Result) function that
 * handles a request and generates a result to be sent to the client.
 *
 * For example,
 * {{{
 * val echo = Action { request =>
 *   Ok("Got request [" + request + "]")
 * }
 * }}}
 *
 * @tparam A the type of the request body
 */
trait Action[A] extends EssentialAction {

  /**
   * Type of the request body.
   */
  type BODY_CONTENT = A

  /**
   * Body parser associated with this action.
   *
   * @see BodyParser
   */
  def parser: BodyParser[A]

  /**
   * Invokes this action.
   *
   * @param request the incoming HTTP request
   * @return the result to be sent to the client
   */
  def apply(request: Request[A]): Future[Result]

  def apply(rh: RequestHeader): Iteratee[Array[Byte], Result] = parser(rh).mapM {
    case Left(r) =>
      Play.logger.trace("Got direct result from the BodyParser: " + r)
      Future.successful(r)
    case Right(a) =>
      val request = Request(rh, a)
      Play.logger.trace("Invoking action with request: " + request)
      Play.maybeApplication.map { app =>
        play.utils.Threads.withContextClassLoader(app.classloader) {
          apply(request)
        }
      }.getOrElse {
        apply(request)
      }
  }(executionContext)

  /**
   * The execution context to run this action in
   *
   * @return The execution context to run the action in
   */
  def executionContext: ExecutionContext = play.api.libs.concurrent.Execution.defaultContext

  /**
   * Returns itself, for better support in the routes file.
   *
   * @return itself
   */
  override def apply(): Action[A] = this

  override def toString = {
    "Action(parser=" + parser + ")"
  }

}

/**
 * A body parser parses the HTTP request body content.
 *
 * @tparam A the body content type
 */
trait BodyParser[+A] extends Function1[RequestHeader, Iteratee[Array[Byte], Either[Result, A]]] {
  self =>

  /**
   * Uses the provided function to transform the BodyParser's computed result
   * when the request body has been parsed.
   *
   * @param f a function for transforming the computed result
   * @param ec The context to execute the supplied function with.
   *        The context is prepared on the calling thread.
   * @return the transformed body parser
   * @see [[play.api.libs.iteratee.Iteratee#map]]
   */
  def map[B](f: A => B)(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) =
        self(request).map { _.right.map(f) }(pec)
      override def toString = self.toString
    }
  }

  /**
   * Like map but allows the map function to execute asynchronously.
   *
   * @param f the async function to map the result of the body parser
   * @param ec The context to execute the supplied function with.
   *        The context prepared on the calling thread.
   * @return the transformed body parser
   * @see [[map]]
   * @see [[play.api.libs.iteratee.Iteratee#mapM]]
   */
  def mapM[B](f: A => Future[B])(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) = self(request).mapM {
        case Right(a) =>
          // safe to execute `Right.apply` in same thread
          f(a).map(Right.apply)(Execution.trampoline)
        case left =>
          Future.successful(left.asInstanceOf[Either[Result, B]])
      }(pec)
      override def toString = self.toString
    }
  }

  /**
   * Uses the provided function to transform the BodyParser’s computed result
   * into another BodyParser to continue with.
   *
   * On Done of the Iteratee produced by this BodyParser, the result is passed
   * to the provided function, and the resulting BodyParser is given the same
   * RequestHeader and the Iteratee produced is used to continue consuming
   * input.
   *
   * @param f the function to produce a new body parser from the result of this body parser
   * @param ec The context to execute the supplied function with.
   *        The context is prepared on the calling thread.
   * @return the transformed body parser
   * @see [[play.api.libs.iteratee.Iteratee#flatMap]]
   */
  def flatMap[B](f: A => BodyParser[B])(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) = self(request).flatMap {
        case Left(e) => Done(Left(e))
        case Right(a) => f(a)(request)
      }(pec)
      override def toString = self.toString
    }
  }

  /**
   * Like flatMap but allows the flatMap function to execute asynchronously.
   *
   * @param f the async function to produce a new body parser from the result of this body parser
   * @param ec The context to execute the supplied function with.
   *        The context is prepared on the calling thread.
   * @return the transformed body parser
   * @see [[flatMap]]
   * @see [[play.api.libs.iteratee.Iteratee#flatMapM]]
   */
  def flatMapM[B](f: A => Future[BodyParser[B]])(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) = self(request).flatMapM {
        case Right(a) =>
          f(a).map { _.apply(request) }(pec)
        case left =>
          Future.successful {
            Done[Array[Byte], Either[Result, B]](left.asInstanceOf[Either[Result, B]])
          }
      }(pec)
      override def toString = self.toString
    }
  }

  /**
   * Uses the provided function to validate the BodyParser's computed result
   * when the request body has been parsed.
   *
   * The provided function can produce either a direct result, which will short
   * circuit any further Action, or a value of type B.
   *
   * Example:
   * {{{
   *   def validateJson[A : Reads] = parse.json.validate(
   *     _.validate[A].asEither.left.map(e => BadRequest(JsError.toFlatJson(e)))
   *   )
   * }}}
   *
   * @param f the function to validate the computed result of this body parser
   * @param ec The context to execute the supplied function with.
   *        The context is prepared on the calling thread.
   * @return the transformed body parser
   */
  def validate[B](f: A => Either[Result, B])(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) = self(request).flatMap {
        case Left(e) => Done(Left(e), Input.Empty)
        case Right(a) => Done(f(a), Input.Empty)
      }(pec)
      override def toString = self.toString
    }
  }

  /**
   * Like validate but allows the validate function to execute asynchronously.
   *
   * @param f the async function to validate the computed result of this body parser
   * @param ec The context to execute the supplied function with.
   *        The context is prepared on the calling thread.
   * @return the transformed body parser
   * @see [[validate]]
   */
  def validateM[B](f: A => Future[Either[Result, B]])(implicit ec: ExecutionContext): BodyParser[B] = {
    // prepare execution context as body parser object may cross thread boundary
    implicit val pec = ec.prepare()
    new BodyParser[B] {
      def apply(request: RequestHeader) = self(request).flatMapM {
        case Right(a) =>
          // safe to execute `Done.apply` in same thread
          f(a).map(Done.apply[Array[Byte], Either[Result, B]](_))(Execution.trampoline)
        case left =>
          Future.successful {
            Done[Array[Byte], Either[Result, B]](left.asInstanceOf[Either[Result, B]])
          }
      }(pec)
      override def toString = self.toString
    }
  }
}

/**
 * Helper object to construct `BodyParser` values.
 */
object BodyParser {

  /**
   * Create an anonymous BodyParser
   *
   * Example:
   * {{{
   * val bodySize = BodyParser { request =>
   *   Iteratee.fold(0) { (state, chunk) => state + chunk.size } map(size => Right(size))
   * }
   * }}}
   */
  def apply[T](f: RequestHeader => Iteratee[Array[Byte], Either[Result, T]]): BodyParser[T] = {
    apply("(no name)")(f)
  }

  /**
   * Create a BodyParser
   *
   * Example:
   * {{{
   * val bodySize = BodyParser("Body size") { request =>
   *   Iteratee.fold(0) { (state, chunk) => state + chunk.size } map(size => Right(size))
   * }
   * }}}
   */
  def apply[T](debugName: String)(f: RequestHeader => Iteratee[Array[Byte], Either[Result, T]]): BodyParser[T] = new BodyParser[T] {
    def apply(rh: RequestHeader) = f(rh)
    override def toString = "BodyParser(" + debugName + ")"
  }

}

/**
 * A builder for generic Actions that generalizes over the type of requests.
 * An ActionFunction[R,P] may be chained onto an existing ActionBuilder[R] to produce a new ActionBuilder[P] using andThen.
 * The critical (abstract) function is invokeBlock.
 * Most users will want to use ActionBuilder instead.
 *
 * @tparam R the type of the request on which this is invoked (input)
 * @tparam P the parameter type which blocks executed by this builder take (output)
 */
trait ActionFunction[-R[_], +P[_]] {
  self =>

  /**
   * Invoke the block.  This is the main method that an ActionBuilder has to implement, at this stage it can wrap it in
   * any other actions, modify the request object or potentially use a different class to represent the request.
   *
   * @param request The request
   * @param block The block of code to invoke
   * @return A future of the result
   */
  def invokeBlock[A](request: R[A], block: P[A] => Future[Result]): Future[Result]

  /**
   * Get the execution context to run the request in.  Override this if you want a custom execution context
   *
   * @return The execution context
   */
  protected def executionContext: ExecutionContext = play.api.libs.concurrent.Execution.defaultContext

  /**
   * Compose this ActionFunction with another, with this one applied first.
   *
   * @param other ActionFunction with which to compose
   * @return The new ActionFunction
   */
  def andThen[Q[_]](other: ActionFunction[P, Q]): ActionFunction[R, Q] = new ActionFunction[R, Q] {
    def invokeBlock[A](request: R[A], block: Q[A] => Future[Result]) =
      self.invokeBlock[A](request, other.invokeBlock[A](_, block))
  }

  /**
   * Compose another ActionFunction with this one, with this one applied last.
   *
   * @param other ActionFunction with which to compose
   * @return The new ActionFunction
   */
  def compose[Q[_]](other: ActionFunction[Q, R]): ActionFunction[Q, P] =
    other.andThen(this)

  def compose(other: ActionBuilder[R]): ActionBuilder[P] =
    other.andThen(this)

}

/**
 * Provides helpers for creating `Action` values.
 */
trait ActionBuilder[+R[_]] extends ActionFunction[Request, R] {
  self =>

  /**
   * Constructs an `Action`.
   *
   * For example:
   * {{{
   * val echo = Action(parse.anyContent) { request =>
   *   Ok("Got request [" + request + "]")
   * }
   * }}}
   *
   * @tparam A the type of the request body
   * @param bodyParser the `BodyParser` to use to parse the request body
   * @param block the action code
   * @return an action
   */
  final def apply[A](bodyParser: BodyParser[A])(block: R[A] => Result): Action[A] = async(bodyParser) { req: R[A] =>
    Future.successful(block(req))
  }

  /**
   * Constructs an `Action` with default content.
   *
   * For example:
   * {{{
   * val echo = Action { request =>
   *   Ok("Got request [" + request + "]")
   * }
   * }}}
   *
   * @param block the action code
   * @return an action
   */
  final def apply(block: R[AnyContent] => Result): Action[AnyContent] = apply(BodyParsers.parse.anyContent)(block)

  /**
   * Constructs an `Action` with default content, and no request parameter.
   *
   * For example:
   * {{{
   * val hello = Action {
   *   Ok("Hello!")
   * }
   * }}}
   *
   * @param block the action code
   * @return an action
   */
  final def apply(block: => Result): Action[AnyContent] = apply(_ => block)

  /**
   * Constructs an `Action` that returns a future of a result, with default content, and no request parameter.
   *
   * For example:
   * {{{
   * val hello = Action.async {
   *   WS.url("http://www.playframework.com").get().map { r =>
   *     if (r.status == 200) Ok("The website is up") else NotFound("The website is down")
   *   }
   * }
   * }}}
   *
   * @param block the action code
   * @return an action
   */
  final def async(block: => Future[Result]): Action[AnyContent] = async(_ => block)

  /**
   * Constructs an `Action` that returns a future of a result, with default content.
   *
   * For example:
   * {{{
   * val hello = Action.async { request =>
   *   WS.url(request.getQueryString("url").get).get().map { r =>
   *     if (r.status == 200) Ok("The website is up") else NotFound("The website is down")
   *   }
   * }
   * }}}
   *
   * @param block the action code
   * @return an action
   */
  final def async(block: R[AnyContent] => Future[Result]): Action[AnyContent] = async(BodyParsers.parse.anyContent)(block)

  /**
   * Constructs an `Action` that returns a future of a result, with default content.
   *
   * For example:
   * {{{
   * val hello = Action.async { request =>
   *   WS.url(request.getQueryString("url").get).get().map { r =>
   *     if (r.status == 200) Ok("The website is up") else NotFound("The website is down")
   *   }
   * }
   * }}}
   *
   * @param block the action code
   * @return an action
   */
  final def async[A](bodyParser: BodyParser[A])(block: R[A] => Future[Result]): Action[A] = composeAction(new Action[A] {
    def parser = composeParser(bodyParser)
    def apply(request: Request[A]) = try {
      invokeBlock(request, block)
    } catch {
      // NotImplementedError is not caught by NonFatal, wrap it
      case e: NotImplementedError => throw new RuntimeException(e)
      // LinkageError is similarly harmless in Play Framework, since automatic reloading could easily trigger it
      case e: LinkageError => throw new RuntimeException(e)
    }
    override def executionContext = ActionBuilder.this.executionContext
  })

  /**
   * Compose the parser.  This allows the action builder to potentially intercept requests before they are parsed.
   *
   * @param bodyParser The body parser to compose
   * @return The composed body parser
   */
  protected def composeParser[A](bodyParser: BodyParser[A]): BodyParser[A] = bodyParser

  /**
   * Compose the action with other actions.  This allows mixing in of various actions together.
   *
   * @param action The action to compose
   * @return The composed action
   */
  protected def composeAction[A](action: Action[A]): Action[A] = action

  override def andThen[Q[_]](other: ActionFunction[R, Q]): ActionBuilder[Q] = new ActionBuilder[Q] {
    def invokeBlock[A](request: Request[A], block: Q[A] => Future[Result]) =
      self.invokeBlock[A](request, other.invokeBlock[A](_, block))
    override protected def composeParser[A](bodyParser: BodyParser[A]): BodyParser[A] = self.composeParser(bodyParser)
    override protected def composeAction[A](action: Action[A]): Action[A] = self.composeAction(action)
  }
}

/**
 * Helper object to create `Action` values.
 */
object Action extends ActionBuilder[Request] {
  def invokeBlock[A](request: Request[A], block: (Request[A]) => Future[Result]) = block(request)
}

/* NOTE: the following are all example uses of ActionFunction, each subtly
 * different but useful in different ways. They may not all be necessary. */

/**
 * A simple kind of ActionFunction which, given a request (of type R), may
 * either immediately produce a Result (for example, an error), or call
 * its Action block with a parameter (of type P).
 * The critical (abstract) function is refine.
 */
trait ActionRefiner[-R[_], +P[_]] extends ActionFunction[R, P] {
  /**
   * Determine how to process a request.  This is the main method than an ActionRefiner has to implement.
   * It can decide to immediately intercept the request and return a Result (Left), or continue processing with a new parameter of type P (Right).
   *
   * @param request the input request
   * @return Either a result or a new parameter to pass to the Action block
   */
  protected def refine[A](request: R[A]): Future[Either[Result, P[A]]]

  final def invokeBlock[A](request: R[A], block: P[A] => Future[Result]) =
    refine(request).flatMap(_.fold(Future.successful _, block))(executionContext)
}

/**
 * A simple kind of ActionRefiner which, given a request (of type R),
 * unconditionally transforms it to a new parameter type (P) to be passed to
 * its Action block.  The critical (abstract) function is transform.
 */
trait ActionTransformer[-R[_], +P[_]] extends ActionRefiner[R, P] {
  /**
   * Augment or transform an existing request.  This is the main method that an ActionTransformer has to implement.
   *
   * @param request the input request
   * @return The new parameter to pass to the Action block
   */
  protected def transform[A](request: R[A]): Future[P[A]]

  final def refine[A](request: R[A]) =
    transform(request).map(Right(_))(executionContext)
}

/**
 * A simple kind of ActionRefiner which, given a request (of type R), may
 * either immediately produce a Result (for example, an error), or
 * continue its Action block with the same request.
 * The critical (abstract) function is filter.
 */
trait ActionFilter[R[_]] extends ActionRefiner[R, R] {
  /**
   * Determine whether to process a request.  This is the main method than an ActionFilter has to implement.
   * It can decide to immediately intercept the request and return a Result (Some), or continue processing (None).
   *
   * @param request the input request
   * @return An optional Result with which to abort the request
   */
  protected def filter[A](request: R[A]): Future[Option[Result]]

  final protected def refine[A](request: R[A]) =
    filter(request).map(_.toLeft(request))(executionContext)
}