NullPointerException when calling service methode in a domain class methode - grails

Question

According to Grails it should be possible to use a service within a domain class. But when I run the following simple example, the grails run-app fails with a NullPointerException: "Cannot invoke method test() on null object"
To reproduce use the following code pieces:
Bootstrap.groovy:
class BootStrap {
def init = { servletContext ->
new Test().test()
}
def destroy = {
}
}
with the service:
#Transactional
class TestService {
def test() {
}
}
and the domain class:
class Test {
def testService
def test() {
testService.test()
}
}
This happens with Grails 3.2.9 and 3.3.0. Is this a Grails error or a GORM failure, not auto injecting the service into domain classes ?
SOLUTION:
For all wondering what the solution is (see answer from erichelgeson) using "static mapping = { autowire true }". But testing both solutions, I found that "static mapping ..." works in Grails 3.3.0 and in 3.2.9, hence setting it globally in application.yml did only work for Grails 3.2.9 but not in Grails 3.3.0 thou.

Answer 1

Recent versions of Grails (3.2.9+) have disabled autowire by default on domain classes for performance reasons. You can re-enable it:
per domain:
static mapping = {
autowire true
}
or globally in application.yml/groovy
grails.gorm.autowire = true
See more # http://gorm.grails.org/6.1.x/hibernate/manual/index.html
Section 1.2.9

Answer 2

You could reenable autowiring per the previous suggestion, but there are performance implications to your whole application for that. It may be worth it, if this is a common situation.
If this is a rare situation for you, you can also access a service as so, in a domain class:
Holders.applicationContext.serviceName.methodName()