Config3
This is small configuration library for Scala utilizing Typesafe Config.
Design
- use typesafe config as backend
- ability to fail when provided config key is unknown/misspelled
- ability to print help on available parameters
- ability to define required and optional parameters
- ability to load parameters from: cmd line arguments, env, java props, files (typesafe)
- ability to print loaded parameters with origins on startup
Example output
Help on available parameters
This is myapp project
Parameters:
Name Value Description
myapp.env environment to use. Try "dev" or "prod"
if no env specified, things will go horribly wrong!
myapp.list [1,2,3] the list
myapp.listmap [a=1,a=2,b=3] the listmap
myapp.map.value required map parameter
myapp.storage_root "./files" file storage root
myapp.web.dev true enable development mode
myapp.web.password application password
Loaded parameters with origins
myapp.env "dev" system properties: 1
myapp.list [1,2,3] reference.conf @ file:/opt/app/conf/reference.conf: 30
myapp.listmap [{"a":1},{"a":2},{"b":3}]reference.conf @ file:/opt/app/conf/reference.conf: 33
myapp.map.value {"x":1,"y":2,"z":3} system properties: 2
myapp.storage_root "./files" reference.conf @ file:/opt/app/conf/reference.conf: 10
myapp.web.dev true reference.conf @ file:/opt/app/conf/reference.conf: 20
myapp.web.password ****** system properties: 3
Usage
Update build.sbt
libraryDependencies += "me.scf37" %% "config3" % "1.0.6"
Define reference.conf
reference.conf contains known configuration keys along with defaults and descriptions.
Example:
#application description
#it will be shown on help screen
myapp {
#application port with default value 8080
port = 8080
#environment name, required parameter, must be provided
env = null
}
Write some code
import com.typesafe.config.ConfigFactory
import me.scf37.config3.Config3
object Main {
def main(args: Array[String]): Unit = {
// load reference configuration
// ConfigFactory.defaultReference() includes system properties and therefore unwanted
val reference = ConfigFactory.parseResources("reference.conf")
// there can be many reference.conf classpath-wise so we process keys for our application only
def isAppConfigKey(key: String) = key.startsWith("myapp.")
// print help if --help requested
if (args.sameElements(Seq("--help"))) {
println(Config3.help(reference, isAppConfigKey))
System.exit(1)
}
// parse command line args -<arg name> <arg value>
val cmdlineConfig = Config3.parse(args) match {
case Left(error) =>
println(error)
System.exit(2)
???
case Right(config) => config
}
// load config, falling back to system properties, environment, myapp.conf and reference config
val config =
cmdlineConfig
.withFallback(ConfigFactory.systemProperties())
.withFallback(ConfigFactory.systemEnvironment())
.withFallback(ConfigFactory.load("myapp.conf"))
.withFallback(reference)
// ensure all required parameters are set and we have no unknown/misspelled keys starting with myapp.
val errors = Config3.validate(reference, config, isAppConfigKey)
if (errors.nonEmpty) {
errors.foreach(println)
System.exit(2)
}
// print resolved configuration
println(Config3.printConfig(reference, config, isAppConfigKey, _.contains("password")))
}
}
Also see me.scf37.config3.Config3Main
