You typically work the other way around and select an AP first and an external antenna after that from the Ordering Guides that are on the website.
From the datasheet of the AP-ANT-25A, you can find that the use case is 'AP-ANT-25A is a dual polarized antenna with nominal 90° H x 90° V beamwidths. This antenna is well suited for 2.4 and 5 GHz sector coverage for access.' and the connectors are 2 pigtails '75 cm (30”) RP-SMA', so it can be used on an AP that is 2x2 MIMO (or 1x1). The AP-304 or AP-504 can be used with this antenna.
If you check the AP-500 series Ordering Guide (get that here), you can see indeed the AP-ANT-25A is stated as a compatible accessory.
From your question I cannot really understand what you are trying to achieve or what your requirements are. It may be good to work with your local Aruba partner or Aruba sales team to find the optimal AP-antenna combination for your deployment. As a general rule-of-thumb, try to stick to APs with built-in antennas. Only use external antennas if there is a very good reason for it (aesthetics indoor, or very specific antenna patterns required indoor or outdoor).