優雅的記錄http請求或響應的資料

摘要： 經常會遇到需要處理http請求以及響應body的場景。而這裡比較大的一個問題是servlet的requestBody或responseBody流一旦被讀取了。就無法二次讀取了。針對這個問題，spring本身提供瞭解決方案，即ContentCachingRequestWrapper/Conten...

經常會遇到需要處理http請求以及響應body的場景。而這裡比較大的一個問題是servlet的requestBody或responseBody流一旦被讀取了。就無法二次讀取了。針對這個問題，spring本身提供瞭解決方案，即ContentCachingRequestWrapper/ContentCachingResponseWrapper。

我們編寫一個過濾器:

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 {
if (this.codeMatched(response.getStatus(), recordCode())) {
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)) {
responseToUse = new ContentCachingResponseWrapper(response);
}

try {
filterChain.doFilter(requestToUse, responseToUse);
} finally {
if (!isAsyncStarted(requestToUse)) {
recordBody(createRequest(requestToUse), createResponse(responseToUse));
}
}
} else {
filterChain.doFilter(request, response);
}
}

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;
}

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();
}

這樣自定義一個filter繼承HttpBodyRecorderFilter，重寫recordBody方法就能自定義自己的處理邏輯了。另外，recordCode可用於定義在請求響應碼為多少的時候才會去記錄body，例如可以定義為只有遇到400或500時才記錄body，用於錯誤偵測。

過濾器的匹配規則比較簡單，如果想要像springmvc那樣進行匹配，我們可以使用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);
}
}

這樣子，PatternMappingFilterProxy裝飾了真正的HttpBodyRecorderFilter，支援傳入urlPatterns，從而實現像springmvc那樣的ant style的匹配。例如對於以下介面：

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