Mocker.java

package com.talios.xted;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class Mocker implements InvocationHandler {

    private Object wrapper;

    private Mocker(Object wrapper) {
        this.wrapper = wrapper;
    }

    public static <T> T mocker(Class<T> iface, Object wrapper) {
        return (T) Proxy.newProxyInstance(wrapper.getClass().getClassLoader(),
                new Class[] {iface}, new Mocker(wrapper));
    }

    @Override
    public Object invoke(Object o, Method method, Object[] objects) throws Throwable {

        Method wrappedMethod = wrapper.getClass().getDeclaredMethod(method.getName(), method.getParameterTypes());

        return wrappedMethod.invoke(wrapper, objects);
    }
}

SomeInterface.java

package com.talios.xted;

public interface SomeInterface {

    String name();
    Integer age();

}

TestMock.java

    @Test
    public void testApp() {
        SomeInterface someInterface = Mocker.mocker(SomeInterface.class, new Object() {
            String name() {
                return "My Name is mock!";
            }
        });

        System.out.println(someInterface.name());
    }