AddRequestHeadersIfNotPresent Filter

The AddRequestHeadersIfNotPresent filter takes a collection of name and value pairs separated by colon. The following example configures an AddRequestHeadersIfNotPresent filter:

application.yml
spring:
  cloud:
    gateway:
      mvc:
        routes:
        - id: add_request_headers_route
          uri: https://example.org
          filters:
          - AddRequestHeadersIfNotPresent=X-Request-Color-1:blue,X-Request-Color-2:green
GatewaySampleApplication.java
import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions.addRequestHeadersIfNotPresent;
import static org.springframework.cloud.gateway.server.mvc.handler.GatewayRouterFunctions.route;
import static org.springframework.cloud.gateway.server.mvc.handler.HandlerFunctions.http;

@Configuration
class RouteConfiguration {

    @Bean
    public RouterFunction<ServerResponse> gatewayRouterFunctionsAddReqHeader() {
        return route(GET("/red"), http("https://example.org"))
                .before(addRequestHeadersIfNotPresent("X-Request-Color-1:blue","X-Request-Color-2:green"));
    }
}

This listing adds 2 headers X-Request-Color-1:blue and X-Request-Color-2:green to the downstream request’s headers for all matching requests. This is similar to how AddRequestHeader works, but unlike AddRequestHeader it will do it only if the header is not already there. Otherwise, the original value in the client request is sent.

Additionally, to set a multi-valued header, use the header name multiple times like addRequestHeadersIfNotPresent("X-Request-Color-1:blue","X-Request-Color-1:green").

AddRequestHeadersIfNotPresent also supports URI variables used to match a path or host. URI variables may be used in the value and are expanded at runtime. The following example configures an AddRequestHeadersIfNotPresent filter that uses a variable:

GatewaySampleApplication.java
@Configuration
class RouteConfiguration {

    @Bean
    public RouterFunction<ServerResponse> gatewayRouterFunctionsAddReqHeader() {
        return route(GET("/red/{segment}"), http("https://example.org"))
                .before(addRequestHeadersIfNotPresent("X-Request-red", "blue-{segment}"));
    }
}
application.yml
spring:
  cloud:
    gateway:
      routes:
      - id: add_request_header_route
        uri: https://example.org
        predicates:
        - Path=/red/{segment}
        filters:
        - AddRequestHeadersIfNotPresent=X-Request-Red:Blue-{segment}