在 spring 引导网关中拦截 Http 请求正文

Question

We are running a bunch of microservices which are guarded by a central gateway (org.springframework.cloud:spring-cloud-starter-gateway:2.1.0) that routes requests to the responsible microservice behind it.

We now want to add a service, that shall get the importent parts of each request as copy (like headers, request path, request body...) via a restful interface for tracking / statistic reasons. To have the code for this only at one place, we want to add it directly to the gateway service.

Implementing WebFilter seems to be a good start for this, but I'm having problems with the request body which is Flux<DataBuffer> .

Subscribing to it causes an error: Only one connection receive subscriber allowed. , because it's a unicast which prohibits multiple receivers of the content.

@Slf4j
@Configuration
public class InterceptConfig implements WebFilter {

    private final StatisticServiceProperties properties;

    @Autowired
    public InterceptConfig(StatisticServiceProperties properties) {
        this.properties = properties;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        log.debug("request intercepted. sending to statistic service : " + request.getURI().toString());

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        request.getBody().subscribe(dataBuffer -> {
            try {
                byteArrayOutputStream.write(dataBuffer.asInputStream().readAllBytes());
            } catch (IOException e) {
                log.debug("couldn't extract body from request", e);
            }
        });

        new StatisticServiceClient(
                new RestTemplate(),
                properties.getBaseUrl() + "/statistic"
        ).createStatistic(
                new CreateStatisticRequest(
                        new Date(),
                        request.getURI(),
                        request.getHeaders(),
                        byteArrayOutputStream.toByteArray()
                )
        );
        return chain.filter(exchange);
    }
}

Is there a way to get the content of the request body without breaking the application?

Edit: 18.11.2019

I found a solution that solves this for me: https://github.com/spring-cloud/spring-cloud-gateway/issues/747#issuecomment-451805283

Answer 1

This is not tested code but try to create ConnectableFlux from original flux. That should allow multiple subscribers:

Flux<DataBuffer> connFlux = request.getBody().share();
Flux.from(connFlux).subscribe(dataBuffer -> {
            try {
                byteArrayOutputStream.write(dataBuffer.asInputStream().readAllBytes());
            } catch (IOException e) {
                log.debug("couldn't extract body from request", e);
            }
        });

Answer 2

Did you try standard spring interceptor approach?
https://www.baeldung.com/spring-mvc-handlerinterceptor https://www.tutorialspoint.com/spring_boot/spring_boot_interceptor.htm