Inject grails application configuration into service

Question

I\'m creating a grails service that will interact with a 3rd party REST API via a Java library. The Java library requires credentials for the REST API by means of a url, use

Answer 1

For contexts where you can't inject the grailsApplication bean (service is not one of those, as described by Jon Cram), for example a helper class located in src/groovy, you can access it using the Holders class:

def MyController {
   def myAction() {
      render grailsApplication == grails.util.Holders.grailsApplication
   }
}

Answer 2

Even though grailsApplication can be injected in services, I think services should not have to deal with configuration because it's harder to test and breaks the Single Responsibility principle. Spring, on the other side, can handle configuration and instantiation in a more robust way. Grails have a dedicated section in its docs.

To make your example work using Spring, you should register your service as a bean in resources.groovy

// Resources.groovy
import com.example.ExampleApiClient

beans {
    // Defines your bean, with constructor params
    exampleApiClient ExampleApiClient, 'baseUrl', 'username', 'password'
}

Then you will be able to inject the dependency into your service

class ExampleService {
    def exampleApiClient

    def relevantMethod(){
        exampleApiClient.action()
    }
}

In addition, in your Config.groovyfile, you can override any bean property using the Grails convention over configuration syntax: beans.<beanName>.<property>:

// Config.groovy
...
beans.exampleApiClient.baseUrl = 'http://example.org'

Both Config.groovy and resources.groovy supports different environment configuration.

Answer 3

The grailsApplication object is available within services, allowing this:

package example

import com.example.ExampleApiClient;

class ExampleService {

    def grailsApplication

    def relevantMethod() {

        def client = new ExampleApiClient(
            grailsApplication.config.apiCredentials.baseUrl
            grailsApplication.config.apiCredentials.username,
            grailsApplication.config.apiCredentials.password
        )

        return client.action();
    }
}