Spring webflux过滤器：如何在查询执行后获得反应器上下文？

Question

@Component
public class MdcWebFilter implements WebFilter {

    @NotNull
    @Override
    public Mono<Void> filter(@NotNull ServerWebExchange serverWebExchange,
                             WebFilterChain webFilterChain) {

        Mono<Void> filter = webFilterChain.filter(serverWebExchange);

        return filter
            .doAfterSuccessOrError(new BiConsumer<Void, Throwable>() {
                @Override
                public void accept(Void aVoid, Throwable throwable) {
                    //Here i would like to be able to access to the request's context
                    System.out.println("doAfterSuccessOrError:" + (throwable==null ? "OK" : throwable.getMessage())+"log the context");
                }
            })
            .doOnEach(new Consumer<Signal<Void>>() {
                @Override
                public void accept(Signal<Void> voidSignal) {
                    //Here i have the context but i don't really know if i am in success or error
                    System.out.println("doOnEach:"+"Log OK/KO and the exception" + voidSignal.getContext());
                }
            })
            .subscriberContext(context -> context.put("somevar", "whatever"));
    }

}

我还尝试了一个flatMap（）和一个mono.subscriberContext（），但我不确定如何正确地插入过滤器（特别是在错误的情况下）。

实现这一目标的最佳方法是什么？

Answer 1

我不确定是否可能从WebFilter中访问请求反应器上下文。WebFilter上下文存在于另一个Mono链中。但是，可以将属性与请求关联起来，并且能够在请求生命期内获取这些属性，这与Servlet API非常类似。

控制器：

@GetMapping(path = "/v1/customers/{customerId}")
public Mono<Customer> getCustomerById(
    @PathVariable("customerId") String customerId,
    ServerWebExchange serverWebExchange)
{
  serverWebExchange.getAttributes().put("traceId", "your_trace_id");
  return customerService.findById(customerId);
}

WebFilter：

public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
    // ...
    String traceId = exchange.getAttributeOrDefault("traceId", "default_value_goes_here");
    //...
    return chain.filter(exchange);
}