How does one make vanilla mobs attack your modded one?

I would also like an answer to this

months later but try this 

https://imgur.com/jzAffOd 

used this code 
((MobEntity)entity).targetSelector.addGoal(1, new NearestAttackableTargetGoal((MobEntity)entity, JakethedogEntity.CustomEntity.class, false, false));

replace the "JakethedogEntity" with your entity public class name. for some reason this doesn't work for indicators when I was testing it, I'm not sure why

use this link instead since the other one messed up 

"https://imgur.com/jzAffOd"

but where do i put it

i followed minotheboy's tutorial but it gives me some errors

ill only put the important parts here
but it seems like it doesnt know what MobEntity and CustomEntity mean

error: cannot find symbol
((MobEntity) entity).targetSelector.addGoal(1, new NearestAttackableTargetGoal((MobEntity) entity, GlungusEntity.CustomEntity.class, false, false));                                      ^
      ^

Can you explain each part like entity public class name, because my dumb brain doesn't know how to use it

Say i have an entity in my mod called "Mouse", and i want it to be attacked by vanilla Cats, then would i replace "JakethedogEntity" with "MouseEntity", and ((MobEntity)entity) with ((CatEntity)entity)?

would that change the code to ((CatEntity)entity).targetSelector.addGoal(1, new NearestAttackableTargetGoal((CatEntity)entity, MouseEntity.CustomEntity.class, false, false));