Fig
You probably don't need another data format, right?
Fig is a very small Scala library which makes it easy to read data out of JSON-based configuration files, with full support for Javascript-style comments. (We're not barbarians here.)
Requirements
- Scala 2.8.1 or 2.9.0-1 or 2.9.1
- Jerkson 0.4.1
Why JSON?
- enough structure for most purposes
- fairly human-readable
- very well supported
- easy to use with configuration management systems like Chef or Puppet
How To Use
First, specify Fig as a dependency:
<repositories>
<repository>
<id>repo.codahale.com</id>
<url>http://repo.codahale.com</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>com.codahale</groupId>
<artifactId>fig_${scala.version}</artifactId>
<version>1.1.7</version>
</dependency>
</dependencies>
Second, write your config file:
{
/* Config allows you to use C-style comments.
* This, for example, is a block comment.
*/
"parent": { // Comments can terminate a line, too.
"child": {
"url": "http://example.com",
// We don't care about comments inside string literals.
"splody-string": "An-a one an-a two an-a // /*wah*/ YAY",
"count": 100,
"names": ["One", "Two", "Three"],
"mapped": {
"1": 1,
"2": 2,
"3": 3
},
"doubly-mapped": {
"1": [1, 2, 3],
"2": [2, 3, 4],
"3": [3, 4, 5]
}
}
}
}
Third, load your config file:
import com.codahale.fig.Configuration
val config = new Configuration("myapp/config.json")
You can also create a new Configuration
instance from a Source
or an
InputStream
.
Fourth, read values from it:
// Load a value directly.
val port = config("http.port").as[Int]
// Load a value as an option.
val uri = config("http.uri").asOption[Int]
// Load a value or a default value.
var server = config("http.server").or("Fig-Powered")
// Load a list of values.
val numbers = config("http.numbers").asList[Int]
// Or a map of values (key are required to be strings)
val properties = config("http.resource").asMap[String]
// Hell, even load a case class.
case class ResourceConfig(name: String, uri: String)
val resource = config("http.resource").as[ResourceConfig]
// Defy type erasure for lists!
val numbers = config("http.more-numbers").asMap[List[Int]]
License
Copyright (c) 2010-2011 Coda Hale
with contributions from
- Bryan J Swift
Published under The MIT License, see LICENSE