Spring Cloud Gateway provides developers with the flexibility to customize and define their own routing configurations. In this tutorial, we’ll see how to do that.

Configuring RouteLocator

Now, let’s define a custom routing configuration using RouteLocator in a Spring Boot application.

Create RouterLocator bean in the application.

@Bean
    public RouteLocator eshopAppRouterConfig(RouteLocatorBuilder routeLocatorBuilder) {
        return routeLocatorBuilder.routes()
                .route(p -> p.path("/eshop/productservice/**")
                        .filters(f -> f.rewritePath("/eshop/productservice/(?<segment>.*)", "/${segment}"))
                        .uri("lb://PRODUCTSERVICE"))
                .build();
    }

Explanation of the code

• Path Matching (path(...)): This route matches any request that starts with /eshop/productservice/.
• Rewrite Path (rewritePath(...)): The filter removes /eshop/productservice/ from the URL before forwarding the request.
• Load Balancer (uri(...)): The request is routed to PRODUCTSERVICE, which is registered in Spring Cloud Load Balancer.

Example Routing Behavior

Incoming Request	Rewritten Path	Forwarded To
/eshop/productservice/items	/items	PRODUCTSERVICE
/eshop/productservice/category/electronics	/category/electronics	PRODUCTSERVICE

addResponseHeaderFilter

You can add a custom header in response like the following:

@Bean
    public RouteLocator eshopAppRouterConfig(RouteLocatorBuilder routeLocatorBuilder) {
        return routeLocatorBuilder.routes()
                .route(p -> p.path("/eshop/productservice/**")
                        .filters(f -> f.rewritePath("/eshop/productservice/(?<segment>.*)", "/${segment}"))
.addResponseHeader("X-Response-Time", LocalDateTime.now().toString()))
                        .uri("lb://PRODUCTSERVICE"))
                .build();
    }

Here, we have added a custom filter X-Response-Time.