* %a - Remote IP address # 远程ip地址
* %A - Local IP address # 本地ip地址
* %b - Bytes sent, excluding HTTP headers, or '-' if zero # 发送的大小
* %B - Bytes sent, excluding HTTP headers # 发送的大小
* %h - Remote host name (or IP address if enableLookups for the connector is false) # 远程主机名
* %H - Request protocol # 请求协议
* %l - Remote logical username from identd (always returns '-') # 远程逻辑名
* %m - Request method (GET, POST, etc.) # 请求方法
* %p - Local port on which this request was received. See also %{xxx}p below. # 本地端口
* %q - Query string (prepended with a '?' if it exists) # 请求字段
* %r - First line of the request (method and request URI) # 请求首行（包括请求方法和请求url和http协议，即%m,%U,%h）
* %s - HTTP status code of the response # 返回状态
* %S - User session ID # 用户session-id
* %t - Date and time, in Common Log Format # 日期格式
* %u - Remote user that was authenticated (if any), else '-' # 远程登录用户
* %U - Requested URL path # 请求url地址
* %v - Local server name # 本地服务名称
* %D - Time taken to process the request in millis. Note: In httpd %D is microseconds. Behaviour will be aligned to httpd in Tomcat 10 onwards.
# 处理请求耗时（毫秒）
* %T - Time taken to process the request, in seconds. Note: This value has millisecond resolution whereas in httpd it has second resolution. Behaviour will be align to httpd in Tomcat 10 onwards.
# 处理请求耗时（秒）
* %F - Time taken to commit the response, in millis # 提交请求耗时（毫秒）
* %I - Current request thread name (can compare later with stacktraces) # 当前处理线程名称
* %X - Connection status when response is completed: # 连接状态
* X = Connection aborted before the response completed.
* + = Connection may be kept alive after the response is sent.
* - = Connection will be closed after the response is sent.
* %{xxx}i write value of incoming header with name xxx # 根据请求头中的字段输出信息
* %{xxx}o write value of outgoing header with name xxx # 根据返回头中的字段输出信息
* %{xxx}c write value of cookie with name xxx # 根据cookie中的字段输出信息
* %{xxx}r write value of ServletRequest attribute with name xxx #
* %{xxx}s write value of HttpSession attribute with name xxx #
* %{xxx}p write local (server) port (xxx==local) or remote (client) port (xxx=remote) # 本地、远程端口
* %{xxx}t write timestamp at the end of the request formatted using the enhanced SimpleDateFormat pattern xxx #规定时间戳