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来源：https://fredal.xin/http-body-recorder

经常会遇到需要处理 http 请求以及响应 body 的场景。

而这里比较大的一个问题是 servle t的 requestBody 或 responseBody 流一旦被读取了就无法二次读取了。

针对这个问题，spring本身提供了解决方案，即：

• ContentCachingRequestWrapper

• ContentCachingResponseWrapper。

我们编写一个过滤器:

public abstract class HttpBodyRecorderFilter extends OncePerRequestFilter {private static final int DEFAULT_MAX_PAYLOAD_LENGTH = 1024 * 512;private int maxPayloadLength = DEFAULT_MAX_PAYLOAD_LENGTH;@Overrideprotected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)throws ServletException, IOException {boolean isFirstRequest = !isAsyncDispatch(request);HttpServletRequest requestToUse = request;if (isFirstRequest && !(request instanceof ContentCachingRequestWrapper)&& (request.getMethod().equals(HttpMethod.PUT.name())|| request.getMethod().equals(HttpMethod.POST.name()))) {requestToUse = new ContentCachingRequestWrapper(request);}HttpServletResponse responseToUse = response;if (!(response instanceof ContentCachingResponseWrapper) && (request.getMethod().equals(HttpMethod.PUT.name())|| request.getMethod().equals(HttpMethod.POST.name()))) {responseToUse = new ContentCachingResponseWrapper(response);}boolean hasException = false;try {filterChain.doFilter(requestToUse, responseToUse);} catch (final Exception e) {hasException = true;throw e;} finally {int code = hasException ? 500 : response.getStatus();if (!isAsyncStarted(requestToUse) && (this.codeMatched(code, AdvancedHunterConfigManager.recordCode()))) {recordBody(createRequest(requestToUse), createResponse(responseToUse));} else {writeResponseBack(responseToUse);}}}protected String createRequest(HttpServletRequest request) {String payload = "";ContentCachingRequestWrapper wrapper = WebUtils.getNativeRequest(request, ContentCachingRequestWrapper.class);if (wrapper != null) {byte[] buf = wrapper.getContentAsByteArray();payload = genPayload(payload, buf, wrapper.getCharacterEncoding());}return payload;}protected String createResponse(HttpServletResponse resp) {String response = "";ContentCachingResponseWrapper wrapper = WebUtils.getNativeResponse(resp, ContentCachingResponseWrapper.class);if (wrapper != null) {byte[] buf = wrapper.getContentAsByteArray();try {wrapper.copyBodyToResponse();} catch (IOException e) {e.printStackTrace();}response = genPayload(response, buf, wrapper.getCharacterEncoding());}return response;}protected void writeResponseBack(HttpServletResponse resp) {ContentCachingResponseWrapper wrapper = WebUtils.getNativeResponse(resp, ContentCachingResponseWrapper.class);if (wrapper != null) {try {wrapper.copyBodyToResponse();} catch (IOException e) {LOG.error("Fail to write response body back", e);}}}private String genPayload(String payload, byte[] buf, String characterEncoding) {if (buf.length > 0 && buf.length < getMaxPayloadLength()) {try {payload = new String(buf, 0, buf.length, characterEncoding);} catch (UnsupportedEncodingException ex) {payload = "[unknown]";}}return payload;}public int getMaxPayloadLength() {return maxPayloadLength;}private boolean codeMatched(int responseStatus, String statusCode) {if (statusCode.matches("^[0-9,]*$")) {String[] filteredCode = statusCode.split(",");return Stream.of(filteredCode).map(Integer::parseInt).collect(Collectors.toList()).contains(responseStatus);} else {return false;}}protected abstract void recordBody(String payload, String response);protected abstract String recordCode();}

这样自定义一个filter继承HttpBodyRecorderFilter，重写recordBody方法就能自定义自己的处理逻辑了。

另外，recordCode方法可用于定义在请求响应码为多少的时候才会去记录body，例如可以定义为只有遇到400或500时才记录body，用于错误侦测。

过滤器的匹配规则比较简单，如果想要像springmvc那样进行匹配，我们可以使用：AntPathMatcher。

class PatternMappingFilterProxy implements Filter {private final Filter delegate;private final List<String> pathUrlPatterns = new ArrayList();private PathMatcher pathMatcher;public PatternMappingFilterProxy(Filter delegate, String... urlPatterns) {Assert.notNull(delegate, "A delegate Filter is required");this.delegate = delegate;int length = urlPatterns.length;pathMatcher = new AntPathMatcher();for (int index = 0; index < length; ++index) {String urlPattern = urlPatterns[index];this.pathUrlPatterns.add(urlPattern);}}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)throws IOException, ServletException {HttpServletRequest httpRequest = (HttpServletRequest) request;String path = httpRequest.getRequestURI();if (this.matches(path)) {this.delegate.doFilter(request, response, filterChain);} else {filterChain.doFilter(request, response);}}private boolean matches(String requestPath) {for (String pattern : pathUrlPatterns) {if (pathMatcher.match(pattern, requestPath)) {return true;}}return false;}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {this.delegate.init(filterConfig);}@Overridepublic void destroy() {this.delegate.destroy();}public List<String> getPathUrlPatterns() {return pathUrlPatterns;}public void setPathUrlPatterns(List<String> urlPatterns) {pathUrlPatterns.clear();pathUrlPatterns.addAll(urlPatterns);}}

这样子，PatternMappingFilterProxy装饰了真正的HttpBodyRecorderFilter，支持传入urlPatterns，从而实现像springmvc那样的ant style的匹配。例如对于以下接口：

@PostMapping("/test/{id}")
public Object test(@PathVariable(value =  "id",required =  true)  final Integer index)  {//do something}

可以设置urlPattern为/test/{id:[0-9]+}

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