Transit in Xiamen. Do I need visa for transit in Xiame?

I am a permanent resident in the United States, I hold a green card, but my passport is from the Philippines. I am going to Korea for vacation for 2 weeks and I have a Korean visa for this travel. From United States, my transit is Xiamen to go to Korea and leaving Korea, my transit is Xiamen again to go back to United States. These connecting flights are all under 24 hours.