How to log request body in spring Webflux Java

Question

I am receiving some XML payload in a POST request and want to see the payload as received for debugging purposes.

Below (my custom WebFilter) code logs the URI and reque

Answer 1

You are doing it partially right except that you are extracting the body at the wrong place. You will have to do it in a ServerHttpRequestDecorator implementation and plug it in the WebFilter implementation.

public class RequestLoggingDecorator extends ServerHttpRequestDecorator {

  private static final Logger LOGGER = LoggerFactory.getLogger(RequestLoggingDecorator.class);

  public RequestLoggingDecorator(ServerHttpRequest delegate) {
    super(delegate);
  }

  @Override
  public Flux<DataBuffer> getBody() {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    return super.getBody().doOnNext(dataBuffer -> {
      try {
        Channels.newChannel(baos).write(dataBuffer.asByteBuffer().asReadOnlyBuffer());
        String body = new String(baos.toByteArray(), StandardCharsets.UTF_8);
        LOGGER.info("Request: payload={}", body);
      } catch (IOException e) {
        e.printStackTrace();
      } finally {
        try {
          baos.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    });
  }
}

Then you can configure this in a WebFilter implementation as follows:

@Configuration
public class RequestLoggingFilter implements WebFilter {
  @Override
  public Mono<Void> filter(ServerWebExchange serverWebExchange, WebFilterChain webFilterChain) {
    ServerWebExchangeDecorator decorator =
        new ServerWebExchangeDecorator(serverWebExchange) {
          @Override
          public ServerHttpRequest getRequest() {
            return new RequestLoggingDecorator(serverWebExchange.getRequest());
          }
        };

    return webFilterChain.filter(decorator);
  }
}

This should log your request body on every incoming Http request.