custom response per uri with jason code

You can do this in an iRule triggered on

when ASM_REQUEST_VIOLATION {
   ...
   if {[HTTP::uri starts_with "/blabla"} {
      HTTP::respond 500 content {{"error":"invalid character", errorCode: "1231231"} } Header {Content-Type} {application/json}
   }
   ...
}

Otherwise, you need to create a new ASM policy that sets the Violation response to an HTTP 500 response as required. Use a Local Traffic Policy to select between the two ASM policies based on the HTTP::uri.

> if I want to give this response to *all* violations on said uri, then would it be better to set this with a traffic policy?

I'm not sure I understand what you are getting asking here.

> Do I need to create three Virtual servers for this? i.e., one with the real vip and two that have a placeholder vip just for the sake of holding the policy?

You don't need to attach the ASM policies to a virtual server. You just create the ASM policies, and then assign them via a manually configured Local Traffic Policy.

Hi,

Using ASM_REQUEST_BLOCKING (https://clouddocs.f5.com/api/irules/ASM_REQUEST_BLOCKING.html) is also a good alternative.

you could also validate in the user request that it is an api request to adapt the answer (json or default web response).

regards