Spring应用中，后台需要拿到前端的请求参数，方便调试问题，一般都是使用Aop进行日志输出，但是在格式错误的时候就没有日志了。本文提供了LoggableFilter可以在参数转换之前就输出请求参数。

问题

Spring应用中，一般使用Aop进行请求参数和返回值的日志输出，但是这里有一个前提，就是用户请求的参数一定好可以转换为方法参数，但是经常前端请求是一个错误的Json格式，参数转换失败，并不会进入AOP所以也就看不到请求参数。只会看到org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error。这就导致定位问题比较困难，所以后台需要一个更好的办法来输出请求参数。

难点：如果直接把HttpServletRequest中的InputStream读取后输出日志，会导致后续业务逻辑读取不到InputStream中的内容，因为流只能读取一次。

参数输出类LoggableFilter

/**
 * @author tenmao
 * @since 2020/11/19
 */
@Slf4j
@Component
public class LoggableFilter extends HttpFilter {

    @Value("${httpLog.enabled:false}")
    private boolean httpLogEnabled;

    @Override
    public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws IOException, ServletException {
        if (!httpLogEnabled) {
            filterChain.doFilter(request, response);
            return;
        }

        ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(request);
        ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(response);

        try {
            filterChain.doFilter(requestWrapper, responseWrapper);
        } finally {
            try {
                HttpRequestLog requestLog = HttpRequestLog.build(requestWrapper);
                HttpResponseLog responseLog = HttpResponseLog.build(responseWrapper);
                log.info("Http Request: {}\n\nHttp Response: {}", requestLog.toMultiLines(), responseLog.toMultiLines());
            } catch (Exception e) {
                log.warn("fail to build http log", e);
            } finally {
                //这一行必须添加，否则就一直不返回
                responseWrapper.copyBodyToResponse();
            }
        }
    }


    @Data
    @Builder
    private static class HttpRequestLog {
        private String clientIp;
        private String method;
        private String uri;
        private Map<String, String[]> parameters;
        private Map<String, String> headers;
        private String body;

        public String toMultiLines() {
            StringBuilder sb = new StringBuilder();
            sb.append("\n>>Start Http Request\n");
            sb.append("Client IP: ").append(clientIp).append("\n")
                    .append(method).append(" ").append(uri);
            if (!CollectionUtils.isEmpty(parameters)) {
                String str = parameters.entrySet().stream()
                        .flatMap(entry -> Arrays.stream(entry.getValue()).map(v -> Pair.of(entry.getKey(), v)))
                        .map(pair -> pair.getFirst() + "=" + pair.getSecond())
                        .collect(Collectors.joining("&"));
                sb.append("?").append(str);
            }
            sb.append("\n");
            headers.forEach((s, s2) -> sb.append(s).append(":").append(s2).append("\n"));
            sb.append("\n");
            sb.append(body);
            sb.append("\n>>End Http Request");
            return sb.toString();
        }

        public static HttpRequestLog build(ContentCachingRequestWrapper request) throws IOException {
            String body = new String(request.getContentAsByteArray(), StandardCharsets.UTF_8);
            String method = request.getMethod();

            return HttpRequestLog.builder()
                    .clientIp(request.getRemoteAddr())
                    .method(method)
                    .uri(request.getRequestURI())
                    .parameters(request.getParameterMap())
                    .headers(getRequestHeaders(request))
                    .body(body)
                    .build();
        }

        private static Map<String, String> getRequestHeaders(HttpServletRequest request) {
            Map<String, String> headers = new HashMap<>();
            Enumeration<String> headerNames = request.getHeaderNames();
            while (headerNames.hasMoreElements()) {
                String headerName = headerNames.nextElement();
                headers.put(headerName, request.getHeader(headerName));
            }
            return headers;

        }
    }

    @Data
    @Builder
    private static class HttpResponseLog {
        private int code;
        private Map<String, String> headers;
        private String body;

        public String toMultiLines() {
            StringBuilder sb = new StringBuilder();
            sb.append("\n<<Start Http Response\n");
            sb.append(code).append("\n");
            headers.forEach((s, s2) -> sb.append(s).append(":").append(s2).append("\n"));
            sb.append("\n");
            sb.append(body);
            sb.append("\n<<End Http Response");
            return sb.toString();
        }

        public static HttpResponseLog build(ContentCachingResponseWrapper responseWrapper) throws IOException {
            return HttpResponseLog.builder()
                    .code(responseWrapper.getStatus())
                    .headers(getResponseHeaders(responseWrapper))
                    .body(new String(responseWrapper.getContentAsByteArray(), StandardCharsets.UTF_8))
                    .build();
        }

        private static Map<String, String> getResponseHeaders(ContentCachingResponseWrapper response) {
            Map<String, String> headers = new HashMap<>();
            Collection<String> headerNames = response.getHeaderNames();
            for (String headerName : headerNames) {
                headers.put(headerName, response.getHeader(headerName));
            }
            return headers;
        }
    }
}

参考

• Spring Boot 记录 Http 请求日志