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javalambdajava-8invokedynamiclambda-metafactory

How to instantiate an object using LambdaMetaFactory?


I have an interface Action:

package action;

public interface Action {
    public String act();
}

Class SimpleAction:


package action;

public class SimpleAction implements Action {

    String action;
    public SimpleAction() {}

    public SimpleAction(String x) {
        this.action = x;
    }

    @Override
    public String act() {
        return "Act method from -" + this.action;
    }
}

Class ComplexAction:



    package action;

    public class ComplexAction implements Action{

        String action;
        public ComplexAction() {}
        public ComplexAction(String x) {
            this.action = x;
        }
        @Override
        public String act() {
            return "Act method from -" + this.action;
        }
    }

I want to create a function which takes the name of class and returns an object of that class. This is what I have so far in my function -

 

    public static Action resultOfActMethod(String objclass){   
        Class clazz = Class.forName(objclass);
        MethodHandles.Lookup lookup = MethodHandles.lookup();
        MethodHandle mh = lookup.findConstructor(clazz,MethodType.methodType(void.class, String.class));
    }


Solution

  • Figured it out.

    public static Action resultOfActMethod(String objclass){    
        Class clazz = Class.forName(objclass);
        MethodHandles.Lookup lookup = MethodHandles.lookup();
        MethodHandle mh = lookup.findConstructor(clazz, MethodType.methodType(void.class, String.class));
        Function<String, Action> constructor = (Function<String, Action>)LambdaMetafactory.metafactory(lookup, "apply",MethodType.methodType(Function.class),
                            mh.type().generic(), mh, mh.type()).getTarget().invokeExact();
        Action action = constructor.apply(objclass);
        return action;
    }