基于4.1.7.RELEASE

Filter處理request log的基類，提供了在filterChain.doFilter調用前后的回調函數(shù)，其實現(xiàn)類有CommonsRequestLoggingFilter，Log4jNestedDiagnosticContextFilter，ServletContextRequestLoggingFilter。

其核心代碼為doFilterInternal方法：

@Override protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)throws ServletException, IOException {boolean isFirstRequest = !isAsyncDispatch(request);HttpServletRequest requestToUse = request;if (isIncludePayload() && isFirstRequest && !(request instanceof ContentCachingRequestWrapper)) {requestToUse = new ContentCachingRequestWrapper(request);}boolean shouldLog = shouldLog(requestToUse);if (shouldLog && isFirstRequest) {beforeRequest(requestToUse, getBeforeMessage(requestToUse));}try {filterChain.doFilter(requestToUse, response);}finally {if (shouldLog && !isAsyncStarted(requestToUse)) {afterRequest(requestToUse, getAfterMessage(requestToUse));}} }

在調用filterChain.doFilter方法前后分別調用beforeRequest和afterRequest，而這兩個方法具體實現(xiàn)由子類決定，根據功能不同來決定記錄日志的方法，

在beforeRequest中和afterRequest中分別調用了? getBeforeMessage，getAfterMessage，這兩個方法代碼如下

private String getBeforeMessage(HttpServletRequest request) {return createMessage(request, this.beforeMessagePrefix, this.beforeMessageSuffix); }private String getAfterMessage(HttpServletRequest request) {return createMessage(request, this.afterMessagePrefix, this.afterMessageSuffix); }

最終都會進入到createMessage中去，只是前綴后綴不同，

before的Msg格式是： Before request [? Msg? ]

after的Msg格式是 ： After request [? Msg? ]

這里的Msg具體內容則由createMessage決定

protected String createMessage(HttpServletRequest request, String prefix, String suffix) {StringBuilder msg = new StringBuilder();msg.append(prefix);msg.append("uri=").append(request.getRequestURI());if (isIncludeQueryString()) {msg.append('?').append(request.getQueryString());}if (isIncludeClientInfo()) {String client = request.getRemoteAddr();if (StringUtils.hasLength(client)) {msg.append(";client=").append(client);}HttpSession session = request.getSession(false);if (session != null) {msg.append(";session=").append(session.getId());}String user = request.getRemoteUser();if (user != null) {msg.append(";user=").append(user);}}if (isIncludePayload() && request instanceof ContentCachingRequestWrapper) {ContentCachingRequestWrapper wrapper = (ContentCachingRequestWrapper) request;byte[] buf = wrapper.getContentAsByteArray();if (buf.length > 0) {int length = Math.min(buf.length, getMaxPayloadLength());String payload;try {payload = new String(buf, 0, length, wrapper.getCharacterEncoding());}catch (UnsupportedEncodingException e) {payload = "[unknown]";}msg.append(";payload=").append(payload);}}msg.append(suffix);return msg.toString(); }

根據具體的參數(shù)設置的不同，其表現(xiàn)出不同的形式，msg的最基本格式為

Before/After request [? uri=xxx? ]

設置includeQueryString=true:

Before/After request [? uri=xxx?a=xx&b=xxx? ]

設置includeClientInfo=true:

Before/After request [? uri=xxx?a=xxx&b=xxx;client=xxx;session=sessionId;user=xxx? ]

設置includePayload=true:

先判斷request的content的長度，如果超過設置maxPayload的長度，則按照maxPayload進行截取，如果出現(xiàn)異常，則payload=[unknown]

Before/After request [? uri=xxx?a=xxx&b=xxx;client=xxx;session=sessionId;user=xxx;payload=xxx/[unknown]? ]

下面來看其子類對應的不同的實現(xiàn)

CommonsRequestLoggingFilter： @Override protected boolean shouldLog(HttpServletRequest request) {return logger.isDebugEnabled(); }@Override protected void beforeRequest(HttpServletRequest request, String message) {logger.debug(message); }@Override protected void afterRequest(HttpServletRequest request, String message) {logger.debug(message); }

其主要是調用初始化時候設置的GenericFilterBean中的logger進行記錄。

Log4jNestedDiagnosticContextFilter：

其采用了Log4j來進行日志記錄。自定義變量

protected final Logger log4jLogger = Logger.getLogger(getClass());

ServletContextRequestLoggingFilter：

使用ServletContext來記錄日志

總結

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