I am attempting to detect when a mob hits something and then check to see if the Entity is listed in an external file.I am wondering how I would do this. This is what I have currently got,
Detect Entity attacking:
 

//Mob attacking
	@SubscribeEvent
	public static void testEntityEvent(LivingHurtEvent event)
	{
		DamageSource damageSource = event.getSource();
		if (damageSource.getTrueSource() instanceof MobEntity)
        { 
			Item air = Item.getItemByID(0);
          	LivingEntity livingEntity = (LivingEntity) damageSource.getTrueSource();
			ItemStack stack = livingEntity.getHeldItemMainhand();
			Item item = stack.getItem();
			if (item != air) 
			{
				System.out.println(DamageType.getFromItem(item));
			}
			
			else
			{
				EntityType<?> entity = damageSource.getTrueSource().getEntity();
				System.out.println(DamageType.getFromEntity(entity));
			}
		}

This is how I check DamageType:
 

@Nonnull
	public static DamageType getFromEntity(EntityType<?> entity)
	{
		if (slashingDamageEntities.contains(entity))
		{
			return SLASHING;
		}
		else if (piercingDamageEntities.contains(entity))
		{
			return PIERCING;
		}
		
		return BLUDGEONING;
	}

And this is how I register the Resource Location:
 

public static final EntityTypeTags.Wrapper slashingDamageEntities = new EntityTypeTags.Wrapper(new ResourceLocation(dungeoncraft.MOD_ID, "slashing_damage_mobs"));
public static final EntityTypeTags.Wrapper piercingDamageEntities = new EntityTypeTags.Wrapper(new ResourceLocation(dungeoncraft.MOD_ID, "piercing_damage_mobs"));

Now I am aware that I am checking the Tags for EntityType<?> instead of Entity but I am wondering how to do it using an Entity instead. Or a better way to do it using EntityType<?> by modifying the first file.

For reference this is my Tags file and the other is very similar.
 

{
	"replace": false,
	"values": [
		"minecraft:chicken",
		"minecraft:fox",
		"minecraft:parrot",
		"minecraft:pufferfish",
		"minecraft:turtle",
		"minecraft:bee",
		"minecraft:wolf",
		"minecraft:cave_spider",
		"minecraft:spider",
		"minecraft:elder_guardian",
		"minecraft:endermite",
		"minecraft:guardian",
		"minecraft:phantom",
		"minecraft:shulker",
		"minecraft:silverfish"
	]
}

 

Search for class EntityTypeTags. This should help you. Also, it should (disclaimer: i didn't bother to try) work the same way as how this docs tell you how to use tags: https://mcforge.readthedocs.io/en/latest/utilities/tags/