Set a beacon active.

BeaconActivator.java

    public static class ReflectionUtils {
        public static String getVersion() {
            return Bukkit.getServer().getClass().getPackage().getName().replace(".", ",").split(",")[3];
        }

        public static Class<?> getNMSClass(String name) {
            Class<?> clazz = null;
            try {
                clazz = Class.forName("net.minecraft.server." + getVersion() + "." + name);
            } catch (ClassNotFoundException e) { e.printStackTrace(); }
            return clazz;
        }

        public static Field getField(Class<?> clazz, String name) {
            Field field = null;
            try {
                field = clazz.getField(name);
            } catch (Exception e) { }
            if (field == null) {
                try {
                    field = clazz.getDeclaredField(name);
                } catch (Exception e) { }
            }
            if (field != null) field.setAccessible(true);
            return field;
        }

        public static Method getMethod(Class<?> clazz, String name, Class<?>... params) {
            Method method = null;
            try {
                method = clazz.getMethod(name, params);
            } catch (Exception e) {}
            if (method == null) {
                try {
                    method = clazz.getMethod(name, params);
                } catch (Exception e) {}
            }
            if (method != null) method.setAccessible(true);
            return method;
        }
    }
    
    public static class WorldUtils {
        public static void setBeaconActive(Block block, boolean state) {
            if (block == null || !(block.getState() instanceof Beacon)) return;
            try {
                Class beaconClass = ReflectionUtils.getNMSClass("TileEntityBeacon");
                Class worldClass = block.getWorld().getClass();
                Object nmsWorld = ReflectionUtils.getMethod(worldClass, "getHandle").invoke(block.getWorld());
                Method tileEntityMethod = ReflectionUtils.getMethod(nmsWorld.getClass(), "getTileEntityAt", Integer.class, Integer.class, Integer.class);
                if (tileEntityMethod != null) {
                    Object beacon = tileEntityMethod.invoke(nmsWorld, block.getX(), block.getY(), block.getZ());
                    Field active;
                    try {
                        ReflectionUtils.getField(beaconClass, "i").set(beacon, state);
                    } catch (Exception ex) {
                        throw ex;
                    }
                }
            } catch (Exception ex) {
                ex.printStackTrace();
                block.getState().update();
            }
        }
    }