仅对某些 content-type 应用 modifyResponseBody

Question

我正在使用 GatewayFilterSpec.modifyResponseBody（标记为 "BETA" 功能）重写 JSON 有效负载。只要响应负载实际上是 content-type application/json，这种方法就可以正常工作。就我而言，不幸的是，这并不总是得到保证，我希望它仅在响应具有 Content-Type: application/json header 时应用 modifyResponseBody，否则跳过过滤器。 Spring Cloud Gateway 可以做到这一点吗？如何做到这一点？谢谢。

现在我明白了：

org.springframework.web.reactive.function.UnsupportedMediaTypeException: Content type 'text/html' not supported
    at org.springframework.web.reactive.function.BodyInserters.lambda$null(BodyInserters.java:329)
    at java.util.Optional.orElseGet(Optional.java:267)
    at org.springframework.web.reactive.function.BodyInserters.lambda$bodyInserterFor(BodyInserters.java:325)

Answer 1

这是一个 "solution"，有各种问题:

package my_package;

import org.reactivestreams.Publisher;
import org.springframework.cloud.gateway.filter.GatewayFilter;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.factory.rewrite.ModifyResponseBodyGatewayFilterFactory;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import static org.springframework.http.MediaType.APPLICATION_JSON;

@Component
@Primary
public class JsonOnlyModifyResponseBodyGatewayFilterFactory extends ModifyResponseBodyGatewayFilterFactory {
    public JsonOnlyModifyResponseBodyGatewayFilterFactory(ServerCodecConfigurer codecConfigurer) {
        super(codecConfigurer);
    }

    @Override
    public GatewayFilter apply(Config config) {
        return new MyModifyResponseGatewayFilter(config);
    }

    public class MyModifyResponseGatewayFilter extends ModifyResponseGatewayFilter {
        MyModifyResponseGatewayFilter(Config config) {
            super(config);
        }

        @Override
        public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
            ServerHttpResponse serverHttpResponse = getServerHttpResponseFromSuper(exchange);
            ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) {
                @Override
                public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                    if (APPLICATION_JSON.isCompatibleWith(getDelegate().getHeaders().getContentType())) {
                        return serverHttpResponse.writeWith(body);
                    }
                    return super.writeWith(body);
                }
            };
            return chain.filter(exchange.mutate().response(responseDecorator).build());
        }

        private ServerHttpResponse getServerHttpResponseFromSuper(ServerWebExchange exchange) {
            ServerHttpResponse[] serverHttpResponse = new ServerHttpResponse[1];
            //noinspection UnassignedFluxMonoInstance
            super.filter(exchange, chain -> {
                serverHttpResponse[0] = chain.getResponse(); // capture the response when the super sets it
                return null;
            });
            return serverHttpResponse[0];
        }
    }
}

所选择的方法代替了仅更改现有 ModifyResponseBodyGatewayFilterFactory 的副本。这允许 Spring Boot Gateway 的版本升级带来 ModifyResponseBodyGatewayFilterFactory 的微小变化。但是由于 JsonOnlyModifyResponseBodyGatewayFilterFactory 非常依赖于 ModifyResponseBodyGatewayFilterFactory 的实现，这很容易被破坏。这个解决方案的另一个缺陷是我必须放置一个 @Primary 注释来避免 required a single bean, but 2 were found 异常，但它会覆盖默认值，这可能会影响 modifyResponseBody 的其他用途。调用 super.filter 而不使用其结果是丑陋的。等等。所以，虽然这个 "works"，但它并没有让我高兴。

仅对某些 content-type 应用 modifyResponseBody

Only apply modifyResponseBody for certain content-type

spring-cloud

spring-cloud-gateway