other dogs keep trying to hump mine

my dog is so chilled out that whenever we are at the dog exercise area all the other dogs try humping him and alfie either stands there or laids down

Ask the owners of the other dogs to stop their dogs doing it! It's very impolite & could cause a rucus!

They are trying to dominate him. I would as Caryll says ask the owners to stop their dogs.

Definitely, tell the owners!

Zeus has got the opposite problem, he always wants to hump other dogs. I always give him the benefit of the doubt and let him play with other dogs, but as soon as he goes to hump, I immediately tell him off and take him away from the dogs. The owners should be telling their dogs off too.