May 5, 2014

Groovy Goodness: Extend ConfigSlurper with Custom Environments Sections

Groovy contains the useful ConfigSlurper for reading in configuration files where settings can be different for different environments. We only have to include an environments block and define values for configuration properties per environment. Since Groovy 2.3 we can add our own conditional configuration blocks and therefore don't have to put everything in an environments block.

In the following sample we define our own configuration block servers and use two environments local and prod. We given the property mail.host different values per environment:

// Configuration script.
def config = '''
// Custom block with setting
// conditional per environment.
servers {
    local {
        mail.host = 'greenmail'

    prod {
        mail.host = 'mail.server'

environments {
    local {
        appName = 'local'
    prod {
        appName = 'production'

// Helper closure to create a new
// ConfigSlurper for the given environment and
// register servers as section with configuration
// per environment.
def createConfig = { env ->
    def configSlurper = new ConfigSlurper(env)
    configSlurper.registerConditionalBlock('servers', env)

// Create configuration slurper and
// set environment to prod.
def configuration = createConfig('prod').parse(config)

assert configuration.mail.host == 'mail.server'
assert configuration.appName == 'production'

// Create configuration slurper and
// set environment to local.
configuration = createConfig('local').parse(config)

assert configuration.mail.host == 'greenmail'
assert configuration.appName == 'local'

Code written with Groovy 2.3.