What is the difference between Groovy's AnnotationNode and Java's annotation?

Question

I've written a library in which I do some introspection on Java fields to have their annotation list (and more specifically to see if they have one or more specific annotations (like - say, @Id , @Child , @Parent ). Here is an example of the kind of code I use :

    @Override
    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
        return mapped.getAnnotation(annotationClass);
    }

Where mapped is a Java Field (and as a consequence has a getAnnotation(Annotation) method). I want to port this method to Groovy.

I've already have understood that using Groovy, I have to replace my Fields (or bean properties) by MetaProperties . however, I face an issue considering the use of these annotations, as it seems that groovy handles them very differently from Java.

So, is it possible to consider a migration path from Java annotations to Groovy AnnotationNode, or will i have to create an abstraction over those concepts ?

Answer 1

I'm not sure about AnnotationNode. Based on the package it's in, I'd assume it has to do with AST Transformations .

In any case, your code should work in Groovy the same as Java. I use JPA in Groovy and have accessed the annotations via Java reflection. If you're having a specific problem, please provide more detail.

You seem confused about "fields" vs "metaProperties". You don't change your fields into metaProperties. Your fields become metaProperties. In other words, a field on a Groovy class is a bean property by default ( you get the getter/setter for free). You can access the properties dynamically using Groovy but they are still Field's in the bytecode.

Below is a little Groovy script demonstrating accessing a bean property and getting it's annotation.

import java.lang.reflect.*

class Person {

  @Deprecated
  String name

}

def me = new Person(name:'dave')

assert me.name == 'dave'
assert me.'name' == 'dave'
assert me.getName() == 'dave'

assert Person.class.getDeclaredField('name') instanceof Field
assert Person.class.getDeclaredField('name').getAnnotations()
assert Person.class.getDeclaredField('name').getAnnotation(Deprecated.class)