`FallbackHeaders` Filter

FallbackHeaders 工厂允许你向在外部应用程序中转发至 fallbackUri 的请求的头中添加 Spring Cloud CircuitBreaker 执行异常详细信息，如下面的场景所示：

application.yml

spring:
  cloud:
    gateway:
      mvc:
        routes:
        - id: ingredients
          uri: lb://ingredients
          predicates:
          - Path=//ingredients/**
          filters:
          - name: CircuitBreaker
            args:
              name: fetchIngredients
              fallbackUri: forward:/fallback
        - id: ingredients-fallback
          uri: http://localhost:9994
          predicates:
          - Path=/fallback
          filters:
          - name: FallbackHeaders
            args:
              executionExceptionTypeHeaderName: Test-Header

GatewaySampleApplication.java

import static org.springframework.cloud.gateway.server.mvc.filter.CircuitBreakerFilterFunctions.circuitBreaker;
import static org.springframework.cloud.gateway.server.mvc.filter.BeforeFilterFunctions.fallbackHeaders;
import static org.springframework.cloud.gateway.server.mvc.filter.LoadBalancerFilterFunctions.lb;
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> gatewayRouterFunctionsCircuitBreakerFallbackToGatewayRoute() {
        return route("ingredients")
                .route(path("/ingredients/**"), http())
                .filter(lb("ingredients"))
                .filter(circuitBreaker("fetchIngredients", URI.create("forward:/fallback")))
                .build()
            .and(route("ingredients-fallback")
                .route(path("/fallback"), http("http://localhost:9994"))
                .before(fallbackHeaders())
                .build());
    }
}

在此示例中，在运行断路器时出现执行异常后，请求将转发到运行在 localhost:9994 上的应用程序中的 fallback 端点或处理程序。FallbackHeaders 筛选器会将包含异常类型、消息和（如果可用）根异常类型和消息的头添加到该请求中。

你可以通过设置以下参数的值（及其默认值）来覆盖配置中的头名称：

executionExceptionTypeHeaderName ("Execution-Exception-Type")
executionExceptionMessageHeaderName ("Execution-Exception-Message")
rootCauseExceptionTypeHeaderName ("Root-Cause-Exception-Type")
rootCauseExceptionMessageHeaderName ("Root-Cause-Exception-Message")

有关断路器和网关的更多信息，请参阅 Spring Cloud CircuitBreaker Filter section。

FallbackHeaders Filter

`FallbackHeaders` Filter