Documentation

You are viewing the documentation for the 2.2.2 release in the 2.2.x series of releases. The latest stable release series is 3.0.x.

§Intercepting requests

§Using Filters

The filter component allows you to intercept requests coming to the application, transform request and responses. Filters provide a nice ability to implement cross-cutting concerns of your application. You can create a filter by extending the Filter trait and then add the filter to Global object. The following example creates an access log filter that logs the result of all the actions:

import play.api.mvc._

object AccessLog extends Filter {
  def apply(next: (RequestHeader) => Future[SimpleResult])(request: RequestHeader): Future[SimpleResult] = {
    val result = next(request)
    play.Logger.info(request + "\n\t => " + result)
    result
  }
}

object Global extends WithFilters(AccessLog)

The Global object extends the WithFilters class that allows you to pass one more filters to form a filter chain.

Note WithFilters now extends the GlobalSettings trait

Here is another example where filter is very useful, check authorization before invoking certain actions:

object AuthorizedFilter {
  def apply(actionNames: String*) = new AuthorizedFilter(actionNames)
}

class AuthorizedFilter(actionNames: Seq[String]) extends Filter {

  def apply(next: (RequestHeader) => Future[SimpleResult])(request: RequestHeader): Future[SimpleResult] = {
    if(authorizationRequired(request)) {
      /* do the auth stuff here */
      println("auth required")
      next(request)
    }
    else next(request)
  }

  private def authorizationRequired(request: RequestHeader) = {
    val actionInvoked: String = request.tags.getOrElse(play.api.Routes.ROUTE_ACTION_METHOD, "")
    actionNames.contains(actionInvoked)
  }


}


object Global extends WithFilters(AuthorizedFilter("editProfile", "buy", "sell")) with GlobalSettings {}

Tip RequestHeader.tags provides lots of useful information about the route used to invoke the action.

§Overriding onRouteRequest

One another important aspect of the Global object is that it provides a way to intercept requests and execute business logic before a request is dispatched to an Action.

Tip This hook can be also used for hijacking requests, allowing developers to plug-in their own request routing mechanism.

Let’s see how this works in practice:

import play.api._
import play.api.mvc._

// Note: this is in the default package.
object Global extends GlobalSettings {

  override def onRouteRequest(request: RequestHeader): Option[Handler] = {
    println("executed before every request:" + request.toString)
    super.onRouteRequest(request)
  }

}

It’s also possible to intercept a specific Action method, using Action composition .

Next: Testing your application