Spring Request Forward Enters the Filter Again

six. Global Filters

The GlobalFilter interface has the same signature as GatewayFilter. These are special filters that are conditionally practical to all routes. (This interface and usage are discipline to change in future milestones).

six.1 Combined Global Filter and GatewayFilter Ordering

When a asking comes in (and matches a Route) the Filtering Web Handler volition add all instances of GlobalFilter and all route specific instances of GatewayFilter to a filter concatenation. This combined filter concatenation is sorted past the org.springframework.cadre.Ordered interface, which can be ready by implementing the getOrder() method or by using the @Gild annotation.

Equally Spring Cloud Gateway distinguishes between "pre" and "post" phases for filter logic execution (see: How It Works), the filter with the highest precedence will be the showtime in the "pre"-phase and the last in the "post"-phase.

ExampleConfiguration.coffee.

                          @Bean                                      @Order(-1)                        public            GlobalFilter a() {            return            (exchange, chain) -> {         log.info("first pre filter");            return            concatenation.filter(exchange).and so(Mono.fromRunnable(() -> {             log.info("third post filter");         }));     }; }                          @Bean                                      @Order(0)                        public            GlobalFilter b() {            return            (exchange, chain) -> {         log.info("second pre filter");            return            concatenation.filter(exchange).then(Mono.fromRunnable(() -> {             log.info("second post filter");         }));     }; }                          @Bean                                      @Lodge(ane)                        public            GlobalFilter c() {            return            (substitution, chain) -> {         log.info("third pre filter");            render            chain.filter(substitution).and then(Mono.fromRunnable(() -> {             log.info("outset mail filter");         }));     }; }

6.2 Forward Routing Filter

The ForwardRoutingFilter looks for a URI in the exchange attribute ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR. If the url has a forward scheme (ie forward:///localendpoint), it will use the Spring DispatcherHandler to handler the request. The path office of the request URL volition be overridden with the path in the forrard URL. The unmodified original url is appended to the list in the ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR attribute.

half dozen.three LoadBalancerClient Filter

The LoadBalancerClientFilter looks for a URI in the exchange attribute ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR. If the url has a lb scheme (ie lb://myservice), it will use the Spring Deject LoadBalancerClient to resolve the name (myservice in the previous instance) to an actual host and port and supercede the URI in the same attribute. The unmodified original url is appended to the list in the ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR attribute. The filter will likewise await in the ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR attribute to see if information technology equals lb and then the same rules utilise.

application.yml.

            spring:                          cloud:                          gateway:                          routes:                          - id: myRoute                          uri: lb://service                          predicates:                          - Path=/service/**

	Note
	By default when a service case cannot exist found in the LoadBalancer a 503 will be returned. You can configure the Gateway to return a 404 past setting spring.deject.gateway.loadbalancer.use404=true.

Note

The isSecure value of the ServiceInstance returned from the LoadBalancer will override the scheme specified in the asking made to the Gateway. For example, if the asking comes into the Gateway over HTTPS simply the ServiceInstance indicates information technology is not secure, then the downstream request will be made over HTTP. The opposite situation can also apply. Notwithstanding if GATEWAY_SCHEME_PREFIX_ATTR is specified for the route in the Gateway configuration, the prefix will be stripped and the resulting scheme from the route URL will override the ServiceInstance configuration.

vi.4 Netty Routing Filter

The Netty Routing Filter runs if the url located in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR exchange aspect has a http or https scheme. Information technology uses the Netty HttpClient to make the downstream proxy request. The response is put in the ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR commutation aspect for utilise in a afterwards filter. (There is an experimental WebClientHttpRoutingFilter that performs the same function, but does not crave netty)

six.v Netty Write Response Filter

The NettyWriteResponseFilter runs if at that place is a Netty HttpClientResponse in the ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR exchange attribute. Information technology is run after all other filters have completed and writes the proxy response back to the gateway client response. (There is an experimental WebClientWriteResponseFilter that performs the same function, but does not require netty)

half-dozen.six RouteToRequestUrl Filter

The RouteToRequestUrlFilter runs if at that place is a Route object in the ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR exchange attribute. It creates a new URI, based off of the request URI, just updated with the URI aspect of the Route object. The new URI is placed in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR exchange attribute`.

If the URI has a scheme prefix, such as lb:ws://serviceid, the lb scheme is stripped from the URI and placed in the ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR for use later in the filter concatenation.

half dozen.7 Websocket Routing Filter

The Websocket Routing Filter runs if the url located in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR substitution attribute has a ws or wss scheme. It uses the Jump Web Socket infrastructure to forward the Websocket asking downstream.

Websockets may be load-balanced past prefixing the URI with lb, such as lb:ws://serviceid.

	Note
	If you are using SockJS as a fallback over normal http, you should configure a normal HTTP route too equally the Websocket Road.

application.yml.

            leap:                          cloud:                          gateway:                          routes:                                 - id: websocket_sockjs_route                          uri: http://localhost:3001                          predicates:                          - Path=/websocket/info/**                                 - id: websocket_route                          uri: ws://localhost:3001                          predicates:                          - Path=/websocket/**

half-dozen.viii Gateway Metrics Filter

To enable Gateway Metrics add together spring-kick-starter-actuator as a project dependency. And then, by default, the Gateway Metrics Filter runs as long as the belongings bound.cloud.gateway.metrics.enabled is not ready to simulated. This filter adds a timer metric named "gateway.requests" with the following tags:

• routeId: The route id
• routeUri: The URI that the API will be routed to
• result: Effect equally classified by HttpStatus.Series
• condition: Http Status of the request returned to the client

These metrics are and then available to exist scraped from /actuator/metrics/gateway.requests and can be hands integated with Prometheus to create a Grafana dashboard.

	Note
	To enable the pometheus endpoint add together micrometer-registry-prometheus as a projection dependency.

6.9 Making An Exchange As Routed

After the Gateway has routed a ServerWebExchange it will mark that exchange as "routed" by calculation gatewayAlreadyRouted to the exchange attributes. In one case a request has been marked as routed, other routing filters will non road the request once more, essentially skipping the filter. There are convenience methods that you can utilize to mark an commutation as routed or check if an exchange has already been routed.

• ServerWebExchangeUtils.isAlreadyRouted takes a ServerWebExchange object and checks if it has been "routed"
• ServerWebExchangeUtils.setAlreadyRouted takes a ServerWebExchange object and marks information technology equally "routed"

avitiaanclecome.blogspot.com

Source: https://cloud.spring.io/spring-cloud-static/spring-cloud-gateway/2.1.0.RELEASE/multi/multi__global_filters.html

Share this post