`AddRequestHeadersIfNotPresent` Filter

AddRequestHeadersIfNotPresent 过滤器使用冒号分隔的一组 name 和 value 对。以下示例配置了一个 AddRequestHeadersIfNotPresent 过滤器：

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"));
    }
}

这个清单为所有匹配请求将 2 个标头 X-Request-Color-1:blue 和 X-Request-Color-2:green 添加到下游请求标头中。这类似于 AddRequestHeader 的工作方式，但与 AddRequestHeader 不同，它仅在标头不存在时才会执行此操作。否则，将发送客户端请求中的原始值。

此外，要设置多值标头，需多次使用标头名称，例如 addRequestHeadersIfNotPresent("X-Request-Color-1:blue","X-Request-Color-1:green")。

AddRequestHeadersIfNotPresent 还支持用于匹配路径或主机的 URI 变量。URI 变量可用于值，并会在运行时进行展开。以下示例配置了一个使用变量的 AddRequestHeadersIfNotPresent 过滤器：

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}

AddRequestHeadersIfNotPresent Filter

`AddRequestHeadersIfNotPresent` Filter