The CRAP Stack, Part 3 – Front-End Routes with a Play server

As I continue to develop my React app that is hosted on a Play backend

, I’ve come across the need to support “front-end routes”; that is, URLs that look like this:

http://myapp.com/foo/bar

Where there is no explicit entry for GET /foo/bar
in Play’s routes
and nor is there a physical asset located in /public/foo/bar
for the Assets controller to return to the client, as we set up in the last instalment

:

# Last of all, fall through to the React app
  GET /       controllers.Assets.at(path="/public",file="index.html")
  GET /*file  controllers.Assets.at(path="/public",file)

As it stands, the last line of routes
will
match, the Assets controller will fail
to find the resource, and your configured “client error handler” will be called to deal with the 404. This is not
what we want for a “front-end route”!

What we want
, is for requests that don’t correspond to a physical asset to be considered a request for a virtual asset – and hence given to the React app. And after a bit of fiddling around, I’ve come up with a FrontEndServingController
that gives me the most efficient possible way of dealing with this. The Gist is available
for your copy-paste-and-improve pleasure, but the key points are:

The fall-through cases at the bottom of routes

become:

GET /       controllers.FrontEndServingController.index
  GET /*file  controllers.FrontEndServingController.frontEndPath(file)

Those methods in FrontEndServingController

just being:

val index = serve(indexFile)

  def frontEndPath(path: String) = serve(path)

  private def serve(path: String) = {
    if (physicalAssets.contains(path)) {
      logger.debug(s"Serving physical resource: '$path'")
      assets.at(publicDirectory, path, true)
    } else {
      logger.debug(s"Serving virtual resource: '$path'")
      // It's some kind of "virtual resource" -
      // a front-end "route" most likely
      assets.at(publicDirectory, indexFile, true)
    }
  }

And the “clever” bit being a recursive scan of the /public
directory when we start up, assembling a definitive (and immutable!) Set[String]

of what’s actually a physical asset path:

lazy val physicalAssets:Set[String] = {
    val startingDirectory = new File(physicalPublicDirectory)
    deepList(startingDirectory)
  }

  private def deepList(f: File): Set[String] = {
    val these = f.listFiles.toSet
    val inHere = these.filter(_.isFile).map { f =>
      f.getPath.replace(physicalPublicDirectory, "")
    }
    val belowHere = these.filter(_.isDirectory).flatMap(deepList)
    inHere ++ belowHere
  }
稿源:The Millhouse Group Blog (源链) | 关于 | 阅读提示

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