如何在 Spring WebFlux 中记录请求和响应主体

问题描述：

我希望使用 Kotlin 在 Spring WebFlux 上的 REST API 中集中记录请求和响应.到目前为止，我已经尝试过这种方法

I want to have centralised logging for requests and responses in my REST API on Spring WebFlux with Kotlin. So far I've tried this approaches

@Bean
fun apiRouter() = router {
    (accept(MediaType.APPLICATION_JSON) and "/api").nest {
        "/user".nest {
            GET("/", userHandler::listUsers)
            POST("/{userId}", userHandler::updateUser)
        }
    }
}.filter { request, next ->
    logger.info { "Processing request $request with body ${request.bodyToMono<String>()}" }
    next.handle(request).doOnSuccess { logger.info { "Handling with response $it" } }
}

这里请求方法和路径记录成功，但是正文是Mono，那么我应该如何记录呢?是否应该反过来，我必须订阅请求正文 Mono 并将其记录在回调中?另一个问题是这里的 ServerResponse 接口无法访问响应正文.我怎么能在这里得到它?

Here request method and path log successfully but the body is Mono, so how should I log it? Should it be the other way around and I have to subscribe on request body Mono and log it in the callback? Another problem is that ServerResponse interface here doesn't have access to the response body. How can I get it here?

我尝试过的另一种方法是使用 WebFilter

Another approach I've tried is using WebFilter

@Bean
fun loggingFilter(): WebFilter =
        WebFilter { exchange, chain ->
            val request = exchange.request
            logger.info { "Processing request method=${request.method} path=${request.path.pathWithinApplication()} params=[${request.queryParams}] body=[${request.body}]"  }

            val result = chain.filter(exchange)

            logger.info { "Handling with response ${exchange.response}" }

            return@WebFilter result
        }

同样的问题:请求主体是 Flux 而没有响应主体.

Same problem here: request body is Flux and no response body.

有没有办法从某些过滤器访问完整的请求和响应以进行日志记录?我有什么不明白的?

Is there a way to access full request and response for logging from some filters? What don't I understand?

答

这或多或少类似于 Spring MVC 中的情况.

This is more or less similar to the situation in Spring MVC.

在 Spring MVC 中，您可以使用 AbstractRequestLoggingFilter 过滤器和 ContentCachingRequestWrapper 和/或 ContentCachingResponseWrapper.这里有许多权衡:

In Spring MVC, you can use a AbstractRequestLoggingFilter filter and ContentCachingRequestWrapper and/or ContentCachingResponseWrapper. Many tradeoffs here:

如果您想访问 servlet 请求属性，您需要实际读取和解析请求正文
记录请求正文意味着缓冲请求正文，这会占用大量内存
如果您想访问响应正文，则需要包装响应并在写入响应正文时缓冲响应正文，以便以后检索

ContentCaching*Wrapper 类在 WebFlux 中不存在，但您可以创建类似的类.但请记住这里的其他要点:

ContentCaching*Wrapper classes don't exist in WebFlux but you could create similar ones. But keep in mind other points here:

在内存中缓冲数据在某种程度上违背了反应式堆栈，因为我们试图在那里非常有效地利用可用资源
您不应该篡改实际的数据流并且刷新频率高于/低于预期，否则您可能会破坏流式传输用例
在那个级别，您只能访问 DataBuffer 实例，这些实例(大致上)是内存高效的字节数组.那些属于缓冲池并被回收用于其他交换.如果这些没有正确保留/释放，则会造成内存泄漏(并且缓冲数据以供以后使用当然适合这种情况)
再次在那个级别，它只是字节，您无权访问任何编解码器来解析 HTTP 正文.如果内容不是人类可读的，我会忘记缓冲内容

buffering data in memory somehow goes against the reactive stack, since we're trying there to be very efficient with the available resources
you should not tamper with the actual flow of data and flush more/less often than expected, otherwise you'd risk breaking streaming uses cases
at that level, you only have access to DataBuffer instances, which are (roughly) memory-efficient byte arrays. Those belong to buffer pools and are recycled for other exchanges. If those aren't properly retained/released, memory leaks are created (and buffering data for later consumption certainly fits that scenario)
again at that level, it's only bytes and you don't have access to any codec to parse the HTTP body. I'd forget about buffering the content if it's not human-readable in the first place

您问题的其他答案:

是的，WebFilter 可能是最好的方法
不，您不应该订阅请求正文，否则您将使用处理程序无法读取的数据；你可以在doOn操作符

flatMap

包装响应应该可以让您访问正在写入的响应主体；但是不要忘记内存泄漏

yes, the WebFilter is probably the best approach
no, you shouldn't subscribe to the request body otherwise you'd consume data that the handler won't be able to read; you can flatMap on the request and buffer data in doOn operators
wrapping the response should give you access to the response body as it's being written; don't forget about memory leaks, though

如何在 Spring WebFlux 中记录请求和响应主体

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