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servlet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; @Override protected 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。
PatternMappingFilterProxy
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); } } @Override public 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; } @Override public void init(FilterConfig filterConfig) throws ServletException { this.delegate.init(filterConfig); } @Override public void destroy() { this.delegate.destroy(); } public List<String> getPathUrlPatterns() { return pathUrlPatterns; } public void setPathUrlPatterns(List<String> urlPatterns) { pathUrlPatterns.clear(); pathUrlPatterns.addAll(urlPatterns); } }
测试
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]+}。
以上代码存在于httpBodyRecorder。