You can use L7 policy for this purpose "Local Traffic ›› Policies : Policy List".
You need to create L7 policy with 3 rules with different ASM policy each and assign this L7 policy to your VS via "Policies" in "Resources" tab for VS.
AFAIU, in your case you need to use next rules:
HTTP URI pass start with "appserver/app1" -> Enable asm policy1
HTTP URI pass start with "appserver/app2" -> Enable asm policy2
HTTP URI pass start with "appserver/app3" -> Enable asm policy3
I want create 3 VS for 3 apps. Normally, i will setup 3 VS and 3 nodes. But now i dont know how to setup nodes when these 3 application running on 1 IP. The difference is only uri. App1 backend is on appserver/app1. App2 backend is on appserver/app2. Only URI has change, but in node i can put fqdn or ip address. I cant setup node like appserver/app1. I hope now its more clear:)
Yes, node is related to IP or FQDN. So, you need to have different IP or FQDN, or create one node and assign it to 3 VS.
In second case, after assigning the same node to each VS, you can create appropriate L7 policy for each VS to allow only traffic with appropriate appserver/app* (is it URL?) pass to backend through appropriate VS.
