spring-cloud-gateway: Webflux base path does not work with Path predicates

Ok, this has literally had me stuck for a full week until I found this ticket. The “promised” documentation changes do not exist in the current Spring Cloud Gateway documentation, so if you add a spring.webflux.base-path things just plain stop working with no explanation of why.

Also, use of a base path is a requirement for our application, because we are adapting an existing Zuul API Gateway, with many people already having access to existing URLs. So, not using spring.webflux.base-path is not an option. And, trying to add the base path to all of the paths in the application also do not work, because things deeper like Actuator and Security start breaking if that is done.

Can someone please update the documentation to either include some of the workarounds in this ticket, or to give the “proper” way to have a base URL for the Spring Cloud Gateway?

The above solution provided by @skerdudou works just fine (though @sumitsarkar’s solution also looks similar but I haven’t checked on it). But for those wondering how to use (register) this custom filter, focus on the class name. The pattern in class name is like {filter name}GatewayFilterFactory. So here, for StripBasePathGatewayFilterFactory, filter name will be StripBasePath, and to use it in application.properties (or yaml) file, we need to define it like - spring.cloud.gateway.routes[0].filters=StripBasePath=1

I had similar issue and quite a similar solution as well, I created a filter to automatically strip the basePath in outgoing requests. This filter don’t need any parameter.

import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.factory.AbstractGatewayFilterFactory;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;

/**
 * @author skerdudou Remove basePath from outgoing request
 */
@Component
public class StripBasePathGatewayFilterFactory extends AbstractGatewayFilterFactory<Object> {

    @Value("${spring.webflux.base-path}")
    private String basePath;

    @Override
    public GatewayFilter apply(Object config) {
        return (exchange, chain) -> {
            ServerHttpRequest req = exchange.getRequest();
            String path = req.getURI().getRawPath();
            String newPath = path.replaceFirst(basePath, "");

            ServerHttpRequest request = req.mutate().path(newPath).contextPath(null).build();

            return chain.filter(exchange.mutate().request(request).build());
        };
    }
}

This was a hard requirement for us so I implemented a workaround:

http
    .addFilterAt(new StripsProxyPathFilter, SecurityWebFiltersOrder.FIRST)
    //etc

Where the StripsProxyPathFilter just takes the substring of the url without the basePath.

I’m interested why the team don’t want to re-implement this - what’s the past experience of zuul that influenced this decision?

Thanks.

Hello and thank you everyone for your work.

I want to mention that this problem still persists and we do not found an official way to handle this issue. When setting a spring.webflux.base-path property, we get a 404 on a simple (previously working) route:

routes:
- id: backend
  uri: http://localhost:9090
  predicates:
  - Path=/api/**
  filters:
  - StripPrefix=1

We are on Spring-boot 3.0.5 & Spring-cloud 2022.0.2 (should be the latests at the moment).