danielshiplett / scg-error

Spring Cloud Gateway Error Demo

A simple demo of Spring Cloud Gateway routing to a normal Spring WebMVC application. If the WebMVC application applies the default header cache control customizer, the 'Cache-Control' header is not properly interpreted by Spring Cloud Gateway's LocalResponseCache filter.

The WebMVC application is configured with:

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        return http
                .headers(headers-> headers.cacheControl(Customizer.withDefaults()))
                .build();
    }

A controller method that doesn't want to be cached can then just return a normal ResponseEntity:

    @GetMapping(value = "/api/not-cached", produces = MediaType.APPLICATION_JSON_VALUE)
    public ResponseEntity<ResponseDto> notCached() {
        return ResponseEntity
                .ok(new ResponseDto(UUID.randomUUID()));
    }

And the header should be:

cache-control: no-cache, no-store, max-age=0, must-revalidate

This is not parsed properly by Spring Cloud Gateway's LocalResponseCache filter. The response will be cached according to the default settings for its route.

Testing

Both the app and gateway modules can be started using gradle bootrun. The application is on port 8081. The gateway is on 8080.

You can curl to the application directly and verify its headers:

curl -v http://localhost:8081/api/not-cached

You can then curl to it through the gateway and see that it is being cached:

curl -v http://localhost:8080/app/api/not-cached

You can also run the same test again, but this time with cached as the endpoint. In this case, Spring Cloud Gateway will not use the max-age=1800 specified by the application.