Question

i’m learning groovy and I have a question concerning its metaprogramming facilities. From what I understand every object in groovy implements the groovy.lang.GroovyObject interface (implicitly added by groovy compiler). The latter interface contains the method getMetaClass() so I can do the following:

class MyGroovyClass{
}
def myGroovyClass = new MyGroovyClass();
println myGroovyClass.metaClass.name

The thing that I don’t understand is how objects compiled by a java compiler like java.lang.String get the metaClass property. Is this property defined in the actually MetaClass object that gets associated with java classes through the MetaClassRegistry?

Answer 1

In addition to methods added through the meta-object protocol, Groovy also augments classes in the JDK with additional methods defined in the groovy.runtime.DefaultGroovyMethods class. List and other collections get methods like each and collect. The same mechanism adds a getMetaClass method to java.lang.Object.