Groovy Trait with Annotation

gistfile1.groovy

import java.lang.annotation.Retention
import java.lang.annotation.RetentionPolicy

@Retention(RetentionPolicy.RUNTIME)
@interface T {
  Class formatter
}

trait A {
  @T(formatter = {})
  String foo
}

trait B {
  def bar() {
    this.class.declaredFields.collectEntries { field ->
      [(field): field.getAnnotation(T)]
    }.findAll { field, annotation ->
      annotation != null
    }
  }
}

class C implements A, B {
  @T()
  String baz
}

def c = new C(foo: 'FOO')
c.bar()
​