在配置文件application.yml里面来配置tomcat accesslog日志：

server:
  port: 80
  tomcat:
    accesslog:
      enabled: true
      directory: D:\Documents\D_代码相关\J_java\sprintboot_study
      prefix: tomcat_access_log
      suffix: .log
      file-date-format: -yyyy-MM-dd
      pattern: '%{X-Real-IP}i - %{Host}i %t "%r" %{Content-Length}i %s %b %D "%{Referer}i" "%{User-Agent}i" %a "%I" "-"'
      rotate: true

日志记录格式(pattern)，形式参照 ：

nginx 日志 log_format：

log_format main '$http_x_real_ip - $http_host [$time_local] "$request" $request_length '
                             '$status $body_bytes_sent $request_time "$http_referer" '
                             '"$http_user_agent" $remote_addr "-" "-" ';

tomcat access log pattern：

pattern: '%{X-Real-IP}i - %{Host}i %t "%r" %{Content-Length}i'
              '%s %b %D "%{Referer}i"'
             '"%{User-Agent}i" %a "%I" "-"'

%{X-Real-IP}i： http X-Real_IP
%{Host}i： http Host
%t： Date and time, in Common Log Format
%r： First line of the request (method and request URI)
%{Content-Length}i： request length
%s： HTTP status code of the response
%b： Bytes sent, excluding HTTP headers, or ‘-’ if zero
%D： Time taken to process the request, in millis
%{Referer}i： http Referer
%{User-Agent}i： http User-Agent
%a： Remote IP address
%I： Current request thread name (can compare later with stacktraces)