Describe the bug

When setting a spring.webflux.base-path property all routes using Path predicates return 404 results

Sample

application.name: demo
server.port: 8080

spring.webflux.base-path: /myapp

spring.cloud.gateway:
  routes:
    - id: google-route
      uri: https://www.google.com/
      predicates:
        - Path=/api/**
      filters:
        - StripPrefix=1

Expected: Visit localhost:8080/myapp/api to see the google homepage (albeit stripped down).
Actual: 404

After digging a bit, I think this is because the PathRoutePredicateFactory uses the URI getRawPath.

Instead it could use a ServerHttpRequest's RequestPath then call pathWithinApplication, which is already set up correctly via the ContextPathCompositeHandler.

It is this ContextPathCompositeHandler which rejects the request earlier if you visit just localhost:8080/api, so the base-path property seems to be broken either way.

Is this change sensible? Or is there a separate feature which allows this functionality?

Thanks for your time.