Just Kitting

Unfiltered gives you many extractors to facilitate pattern matching, and it might be helpful to create some extractors specific to an application, but often you want to factor-out broader functionality. That’s where kits come in.

The GZip Kit

We first had the idea for kits when considering how best to support GZip response encodings. An extractor to match an Accept-Encoding header for gzip would help, and a ResponseFunction to compress the response stream, but these would have to be repeated for every case expression.

The GZip kit is a higher level abstraction that can be applied at once to full intent function. The kit will examine the request first, and if appropriate, prepends a compressing function to the response function chain provided by the intent.

GZip Kit Definition

This part is already done for you in unfiltered-libary, but in case you are curious this is how the GZip kit is defined.

copysourceobject GZip extends unfiltered.kit.Prepend {
  def intent = unfiltered.Cycle.Intent[Any,Any] {
    case Decodes.GZip(req) =>
      ContentEncoding.GZip ~> ResponseFilter.GZip
  }
}

Unlike a plan’s intent function, this one defines the conditions for which its response function is prepended another intent’s. It sets a header and a FilterOutputStream for the response.

GZip Usage

This is a very simple plan that will compress its responses if the user-agent supports it:

copysourceobject EchoPlan extends unfiltered.filter.Plan {
  def intent = unfiltered.kit.GZip {
    case Path(path) => ResponseString(path)
  }
}

Do Kit Yourself

The higher level abstraction provided by kits can be applied to problems specific to an application just as well as for general problems. Don’t be afraid to experiment, and if you happen to make something that does solve a general problem, please share it!