Question

Using Groovy’s package name convention, I can intercept Groovy method calls to a Java method like so:

package groovy.runtime.metaclass.org.myGang.myPackage  class FooMetaClass extends groovy.lang.DelegatingMetaClass {     FooMetaClass(MetaClass delegate)     {         super(delegate);     }      public Object getProperty(Object a, String key)     {         return a.someMethod(key)     } } 

This works fine if I really create an object of class Foo:

def myFoo = new Foo() def fooProperty = myFoo.bar // metaclass invokes myFoo.someMethod('bar') 

However what if Foo is an interface, and I want to intercept method calls to any implementation of it?

def myFoo = FooFactory.create()   // I don't know what class this will be fooProperty = myFoo.bar 

Is there a way to achieve this without having a DelegatingMetaClass for every known implementation of the Interface?

Answer 1

You can create a class named ‘groovy.runtime.metaclass.CustomMetaClassCreationHandle’ to globally handle metaclass creation process.

Inside this class, you can override this method:

protected MetaClass createNormalMetaClass(Class theClass, MetaClassRegistry registry) {   // if theClass instanceof Foo, return your special metaclass   // else return super.createNormalMetaClass(theClass, registry) }