Loading runtime config from JSON in Grails

Config.groovy

// ... rest of Config.groovy content goes above this line to ensure that
// the JSON overrides existing settings.

ConfigLoader.addEntries(loadJson(fetchJson()), this)
def fetchJson() { return System.getenv("GRAILS_APP_CONFIG") }
def loadJson(content) { return content ? grails.converters.JSON.parse(content) : [:] }

ConfigLoader.groovy

// e.g. in grails-app/utils/ConfigLoader.groovy

class ConfigLoader {

    static void addEntries(Map data, obj = null) {
        data?.each { key, value ->
            if (value instanceof Map) {
                addEntries(value, obj.getProperty(key))
            }
            else obj.setProperty(key, value)
        }
    }
}

With this code, you can add an environment variable containing JSON data that overrides the settings in Config.groovy:

export GRAILS_APP_CONFIG='{"dummy": {"test": 1, "str": "Stuff", "l": [2, 3, 6]}}'

This is useful for environments (such as clouds) in which you can't add a config file to the local file system.