Spring-web源码解析之Filter-AbstractRequestLoggingFilter

基于4.1.7.RELEASE

Filter处理request log的基类，提供了在filterChain.doFilter调用前后的回调函数，其实现类有CommonsRequestLoggingFilter，Log4jNestedDiagnosticContextFilter，ServletContextRequestLoggingFilter。

其核心代码为doFilterInternal方法：

@Overrideprotected 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));      }   }}

在调用filterChain.doFilter方法前后分别调用beforeRequest和afterRequest，而这两个方法具体实现由子类决定，根据功能不同来决定记录日志的方法，

在beforeRequest中和afterRequest中分别调用了  getBeforeMessage，getAfterMessage，这两个方法代码如下

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

最终都会进入到createMessage中去，只是前缀后缀不同，

before的Msg格式是： Before request [  Msg  ]

after的Msg格式是 ： After request [  Msg  ]

这里的Msg具体内容则由createMessage决定

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();}

根据具体的参数设置的不同，其表现出不同的形式，msg的最基本格式为

Before/After request [  uri=xxx  ]

设置includeQueryString=true:

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

设置includeClientInfo=true:

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

设置includePayload=true:

先判断request的content的长度，如果超过设置maxPayload的长度，则按照maxPayload进行截取，如果出现异常，则payload=[unknown]

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

下面来看其子类对应的不同的实现

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

其主要是调用初始化时候设置的GenericFilterBean中的logger进行记录。

Log4jNestedDiagnosticContextFilter：

其采用了Log4j来进行日志记录。自定义变量

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

ServletContextRequestLoggingFilter：

使用ServletContext来记录日志