Support dynamic paths in route URI using SetRequestUri filter

[stepancar]

Background

Spring Cloud Gateway does not support dynamic path segments directly in the uri field of a route. This limitation makes it challenging to forward requests to upstream services whose hostnames or paths depend on request parameters (e.g. a path variable like {appId}).

What’s Changed

This PR introduces an update to the routing configuration that leverages the SetRequestUri GatewayFilter factory to dynamically construct the request URI based on path variables. By using URI templates supported by Spring Framework, we can now rewrite the request URI at runtime with values extracted from the incoming request path.

Example Configuration

spring:
  cloud:
    gateway:
      routes:
      - id: seturi_route
        uri: no://op
        predicates:
        - Path=/{appId}/**
        filters:
        - SetRequestUri=http://{appId}.internal.com

For a request path of /red-application/blue, this sets the uri to http://red-application.internal.com before making the downstream request and the final url, including path is going to be http://red-application.indernal.com/red-application/blue

Additional notes

This filter is similar to

RequestHeaderToRequestUriGatewayFilterFactory but more generic

[stepancar]

@spencergibb, sorry, I didn't figure out how to request review, expected automatic PR assign.
Could you look at it? Thank you!

[ryanjbaxter]

Why throw then catch this exception only to return Optional.ofNullable(null)? Couldn't you just call log.info and then return here?

[stepancar]

@ryanjbaxter , yeah, you are right! fixed, thank you!

[ryanjbaxter]

Can you take a look at the CI build?

[stepancar]

@ryanjbaxter , thank you, updated test, AFAIK I can't trigger the CI build myself to check everything correct