Context Path with Webflux

Question

I've been trying to find a way to set the context path for a webflux application. I know I can configure it using

server.servlet.context-path

if I deploy a servlet, but I would like to achieve it with webflux, without having to explicitly add the path to every route or use MVC.

Answer 1

I was having the same issue since the loader balancer bases on the context path to route to different back end apps. One way to get around Spring Boot Webflux w/ the context path is using variables in the @XXXXMapping annotations. For instance @RequestMapping(value = "${server.servlet.context-path}/subpath")

Answer 2

According to this

There is servlet in the name of the property which should be a hint that won't work with webflux.

With springboot v2.3, you can put this in your properties file

spring.webflux.base-path=/your-path

release-notes reference: https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.3-Release-Notes#configurable-base-path-for-webflux-applications

Answer 3

Here is an example of configuring the context path for WebFlux using Netty server based on a comment by @Dmytro Boichenko. You can also include customizers to configure the port and other properties.

@Configuration
public class NettyServerConfig {

    @Value("${server.port}")
    private int port;

    @Value("${server.context.path}")
    private String contextPath;

    @Bean
    public NettyReactiveWebServerFactory nettyReactiveWebServerFactory() {
            NettyReactiveWebServerFactory webServerFactory = new NettyReactiveWebServerFactory() {
                @Override
                public WebServer getWebServer(HttpHandler httpHandler) {
                    Map<String, HttpHandler> handlerMap = new HashMap<>();
                    handlerMap.put(contextPath, httpHandler);
                    return super.getWebServer(new ContextPathCompositeHandler(handlerMap));
                }
        };
        webServerFactory.addServerCustomizers(portCustomizer());
        return webServerFactory;
    }

    public NettyServerCustomizer portCustomizer() {
        return new NettyServerCustomizer() {
            @Override
            public HttpServer apply(HttpServer httpServer) {
                return httpServer.port(port);
            }
        };
    }
}

Answer 4

For use cases where WebFlux application is behind load balancer/proxy you can use dedicated class - ForwardedHeaderTransformer that will extract path context from X-Forwarded-Prefix and will add it to ServerHttpRequest.

Doing so you won't need to modify global context-path (which does not make sense in WebFlux)

More about it here: https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#webflux-web-handler-api

Answer 5

For Undertow I managed to add a context path by creating a customized UndertowReactiveWebServerFactory:

 @Bean
public UndertowReactiveWebServerFactory undertowReactiveWebServerFactory(
        @Value("${server.servlet.context-path}") String contextPath) {
    return new UndertowReactiveWebServerFactory() {
        @Override
        public WebServer getWebServer(HttpHandler httpHandler) {
            Map<String, HttpHandler> handlerMap = new HashMap<>();
            handlerMap.put(contextPath, httpHandler);
            return super.getWebServer(new ContextPathCompositeHandler(handlerMap));
        }
    };
}

Answer 6

You can use web Filter, as mentioned in above answers, but you can do one more thing. Write a Base Controller and Extend every class to that Base Controller. For example:

Base Controller.java

@RestController
@RequestMapping("/{base_url}")
public abstract class BaseController {
}

NewController.java

@RestController
public class NewController extends BaseController{
  @Autowired
  DatabaseClient databaseClient;

  @GetMapping("/status")
  public Mono<Map<String, String>> status() {
    return databaseClient.execute("SELECT 'ok'").
      map(row -> singletonMap("status", row.get(0, String.class)))
      .one();
  }
}

So now you can hit /{base_url}/status