Change HTTP method of request in-flight

I have a use-case for redirecting POST requests to /login to a static resource (the inescapable HTML Form of Doom) served by the gateway itself.

In the gateway, the best way I found to serve static resources is using the spring.webflux.static-path-pattern and spring.resources.static-locations properties, which delegate to the underpinning WebFlux framework. However, this will be able to serve only GET requests (besides HEAD and OPTIONS, which as expected return no content), while all other methods return 405.

Now, I would not say that accepting only GET is a wrong behavior for the serving of static resources. I would, however, appreciate the possibility of "normalizing" the request in the gateway before it lands on the underpinning WebFlux infrastructure, pretty much the same way we can modify a URI with org.springframework.cloud.gateway.route.builder.GatewayFilterSpec#changeRequestUri before it is forwarded to the other systems.

Any ideas?

Start by reading GatewayFilterSpec#changeRequestUri and the handling of spring.webflux.static-path-pattern and spring.resources.static-locations. Trace where the request reaches the underlying WebFlux static-resource infrastructure and determine whether method normalization is supported before that point. Done means the issue has a defined gateway behavior for redirecting POST requests to static resources, with tests covering the resulting method handling.