How to access Grails configuration in Grails 2.0?

I have obtained the latest Grails 2.0 milestone, and I am seeing a deprecation warning for the ConfigurationHolder class:

org.codehaus.groovy.grails.commons.ConfigurationHolder

The deprecation message simply says "Use dependency injection instead" which is not very helpful to me. I understand dependency injection, but how can I wire up a bean with the proper Grails configuration so I can access it at runtime? I need to access the configuration from places other than my Controllers and Tags (such as BootStrap).

Solution

If you need it in an artifact that supports dependency injection, simply inject grailsApplication

class MyController {
    def grailsApplication

    def myAction = {
        def bar = grailsApplication.config.my.property
    }
}

If you need it in a bean in, say, src/groovy or src/java, wire it up using conf/spring/resources.groovy

// src/groovy/com/example/MyBean.groovy
class MyBean {
    def grailsApplication

    def foo() {
        def bar = grailsApplication.config.my.property
    }
}

// resources.groovy
beans = {
    myBean(com.example.MyBean) {
        grailsApplication = ref('grailsApplication')
        // or use 'autowire'
    }
}

Anywhere else, it's probably easiest to either pass the configuration object to the class that needs it, or pass the specific properties that are needed.

// src/groovy/com/example/NotABean.groovy
class NotABean {
    def foo(def bar) {
       ...
    }
}

// called from a DI-supporting artifact
class MyController {
    def grailsApplication
    def myAction = {
        def f = new NotABean()
        f.foo(grailsApplication.config.my.property)
    }
}

Update:

Burt Beckwith recently wrote a couple of blog posts on this. One discusses using getDomainClass() from within domain classes, while the other offers the option of creating your own holder class (if none of the solutions above are appropriate).