Retrieve Annotation from AnnotationReference and create dispatch methods

Question

Is it possible to create dispatch methods over Annotations. I'm trying to create the following scenario:

def generateField(FieldDeclaration field, ClassDeclaration clazz) {
    '''
        «field.annotations.map[it.generateAnnotation(field)].join»
        '''
}

def dispatch generateAnnotation(Password annotation, FieldDeclaration field){
    '''//Password field'''
}

def dispatch generateAnnotation(Boolean annotation, FieldDeclaration field){
    '''//Boolean field'''
}

the defined annotations:

annotation Boolean {

}

annotation Password {

}

How can I access the annotation over the AnnotationDeclaration class?

Answer 1

AnnotationReference represents an instance of annotation. It provides an API to access values of an instance as well as a type:

val passwordAnnotation = Password.findTypeGlobally
val booleanAnnotation = Boolean.findTypeGlobally

val AnnotationReference annotation = field.annotations.head
// get a type
val annotationType = annotation.annotationTypeDeclaration
// check whether the type is Password
if (passwordAnnotation.isAssignableFrom(annotationType)) {
    // get a value of 'myValue' field as integer
    val int value = annotation.getIntValue('myValue')
    …
} else if (booleanAnnotation.isAssignableFrom(annotationType)) {
    …
} else if (…) {
    …
}