Spring Support custom resolution of empty strings in ResourceWebHandler

The empty string can be resolved as index.html in a custom ResourceResolver. It is useful when deploying front-end services.

Here is an example:

String fallBack = "/index.html";
new ResourceResolver() {
    @Override @NonNull
    public Mono<Resource> resolveResource(ServerWebExchange exchange, @NonNull String requestPath, @NonNull List<? extends Resource> locations, @NonNull ResourceResolverChain chain) {
        return chain
                .resolveResource(exchange, requestPath, locations)
                .switchIfEmpty(Mono.defer(()->chain.resolveResource(exchange, fallBack, locations)));
    }

    @Override @NonNull
    public Mono<String> resolveUrlPath(@NonNull String resourcePath,@NonNull List<? extends Resource> locations,@NonNull ResourceResolverChain chain) {
        return chain
                .resolveUrlPath(resourcePath, locations)
                .switchIfEmpty(Mono.defer(()->chain.resolveUrlPath(fallBack, locations)));
    }
}

Its function is similar to that in nginx:

location / {
  try_files $uri $uri/ @router;
}
location @router {
  rewrite ^.*$ /index.html last;
}

Comment From: rstoyanchev

ResourceWebHandler isn't really meant to serve HTML pages. In Spring MVC there is the ViewControllerRegistry that lets you map a URL to an HTML view. There is no equivalent in WebFlux yet but you could use a simple controller:

@Controller
class ViewController {

    @GetMapping
    public String handle() {
        return "/welcome.html";
    }

}

Comment From: trionfordring

Thank you for your guidance.