Spray routing - Notes from Scala meet up

gistfile1.md

Spray routing (@agemooij)

• Spray should be run standalone in spray-can, since you don't want to encapsulate high-performant actor inside a low-performant container
• Spray natively supports Futures:

def getEmployees: Future[List[Employees]] = ???
route = get { complete(OK, getEmployees)}

• Spray runs within one actor. The canonical way to write Spray directives is to write non-blocking directives rather than using more actors.
• Spray has a long-list of built-in directives. Check them out.
• Directives can be chained with &. For example

(decompressRequest() & compressResponseIfRequested()) {...}

• Spray 1.* has a confusing behaviour. Running the following:

val route: Route = get { 
	println("Hello"); 
	complete("world!")
}

will print Hello at the beginning of the program, instead of at each get request. This is because the inner code is a function which will be creating at start:

val inner = { 
	println("Hello"); 
	complete("world!")
}
val route: Route = get inner

Will be fixed in Spray 2.0

• Dealing with failures:

  • If a directive is not matched, it returns a Rejection. If all directives returns a Rejection, the most concrete rejection is returned
  • Error message can be customized by providing your own RejectionHandler
  • Rejections can be tested against, you can check on the rejection object within the unit tests
  • similarly, there is a default ExceptionHandler and you can write custom rejection handler

• Spray is integrated with spray-json:

  • Error in json unmarshalling throws an Exception. Spray engine turns it into Rejection