原本tomcat的日志格式如下：
<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log." suffix=".txt" pattern="%h %l %u %t "%r" %s %b" resolveHosts="false"/>

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我们要在日志中显示时间的话，需要添加%T：

下面表是tomcat日志格式各值代表的意思：
Values Description

• %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 hostname (or IP address if enableLookups for the connector isfalse)
• %H Request protocol
• %l Remote logical username from identd
• %m Request method (GET, POST, and so on)
• %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)
• %U Requested URL path
• %v Local server name
• %D Time taken to process the request, in milliseconds
• %T Time taken to process the request, in seconds
• %I Current request thread name (can compare later with stack t

网站栏目：Tomcat值，改变日志的格式
转载来源：http://cdweb.net/article/ggcedi.html