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) 
