Tomcat日志格式自定义
设置日志显示信息格式，默认情况下，Tomcat的访问日志是不记录的。需要在serve.xml中修改配置，去掉注释。
<!--
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="logs" prefix="localhost_access_log." suffix=".txt"
pattern="common" resolveHosts="false"/>
-->
将注释去掉即可。
<Valve className="org.apache.catalina.valves.AccessLogValve"
directory="logs" prefix="localhost_access_log." suffix=".txt"
pattern="common" resolveHosts="false"/>
-->
将注释去掉即可。
如果要调整日志记录的字段，需要修改pattern属性值，common是默认的属性，其值为： %h %l %u %t %r %s
%b
各符号表示为（下面描述摘自Tomcat官方文档）：
*
%a - Remote IP address
* %A - Local IP address
* %b - Bytes sent, excluding HTTP headers, or '-' if zero
* %B - Bytes sent, excluding HTTP headers
* %h - Remote host name (or IP address if resolveHosts is false)
* %H - Request protocol
* %l - Remote logical username from identd (always returns '-')
* %m - Request method (GET, POST, etc.)
* %p - Local port on which this request was received
* %q - Query string (prepended with a '?' if it exists)
* %r - First line of the request (method and request URI)
* %s - HTTP status code of the response
* %S - User session ID
* %t - Date and time, in Common Log Format
* %u - Remote user that was authenticated (if any), else '-'
* %U - Requested URL path
* %v - Local server name
* %D - Time taken to process the request, in millis
* %T - Time taken to process the request, in seconds
There is also support to write information from the cookie, incoming header,
* %A - Local IP address
* %b - Bytes sent, excluding HTTP headers, or '-' if zero
* %B - Bytes sent, excluding HTTP headers
* %h - Remote host name (or IP address if resolveHosts is false)
* %H - Request protocol
* %l - Remote logical username from identd (always returns '-')
* %m - Request method (GET, POST, etc.)
* %p - Local port on which this request was received
* %q - Query string (prepended with a '?' if it exists)
* %r - First line of the request (method and request URI)
* %s - HTTP status code of the response
* %S - User session ID
* %t - Date and time, in Common Log Format
* %u - Remote user that was authenticated (if any), else '-'
* %U - Requested URL path
* %v - Local server name
* %D - Time taken to process the request, in millis
* %T - Time taken to process the request, in seconds
There is also support to write information from the cookie, incoming header,
the Session or something else in the ServletRequest. It is
modeled after the apache syntax:
* %{xxx}i for incoming headers
* %{xxx}c for a specific cookie
* %{xxx}r xxx is an attribute in the ServletRequest
* %{xxx}s xxx is an attribute in the HttpSession
* %{xxx}i for incoming headers
* %{xxx}c for a specific cookie
* %{xxx}r xxx is an attribute in the ServletRequest
* %{xxx}s xxx is an attribute in the HttpSession
通常情况下，为便于分析网站瓶颈，将pattern=“%h %l %u %t "%r" %s %b %D”，其中D代表处理该请求所消耗的毫秒数，
如此可以方便找到问题，提高系统性能。
http://blog.sina.com.cn/s/blog_6c9a9a870100m2ak.html
http://blog.chinaunix.net/uid-20691565-id-3938220.html
