Log4j输出格式控制--log4j的PatternLayout参数含义

我会带着你远行 2022-06-02 04:26 126阅读 0赞

做项目被log4j的输出格式化参数搞烦了，索性把API的相关部分大致翻译一下，原文参见 [http://logging.apache.org/log4j/docs/api/org/apache/log4j/PatternLayout.html][http_logging.apache.org_log4j_docs_api_org_apache_log4j_PatternLayout.html]

<table style="border-collapse:collapse; border-spacing:0px; max-width:100%; background-color:transparent"> 
 <tbody style=""> 
  <tr style=""> 
   <th style="text-align:left"><span style="margin:0px; padding:0px; font-weight:400; color:rgb(255,255,255)">参数</span></th> 
   <th style="text-align:left"><span style="margin:0px; padding:0px; font-weight:400; color:rgb(255,255,255)">说明</span></th> 
   <th colspan="2" style="text-align:left"><span style="margin:0px; padding:0px; font-weight:400; color:rgb(255,255,255)">例子</span></th> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %c 
    </div> </td> 
   <td style="">列出logger名字空间的全称，如果加上{&lt;层数&gt;}表示列出从最内层算起的指定层数的名字空间</td> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      log4j配置文件参数举例 
    </div> </td> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      输出显示媒介 
    </div> </td> 
  </tr> 
  <tr style=""> 
   <td colspan="2" style="">假设当前logger名字空间是"a.b.c"</td> 
  </tr> 
  <tr style=""> 
   <td style="">%c</td> 
   <td style="">a.b.c</td> 
  </tr> 
  <tr style=""> 
   <td style="">%c{2}</td> 
   <td style="">b.c</td> 
  </tr> 
  <tr style=""> 
   <td style="">%20c</td> 
   <td style="">（若名字空间长度小于20，则左边用空格填充）</td> 
  </tr> 
  <tr style=""> 
   <td style="">%-20c</td> 
   <td style="">（若名字空间长度小于20，则右边用空格填充）</td> 
  </tr> 
  <tr style=""> 
   <td style="">%.30c</td> 
   <td style="">（若名字空间长度超过30，截去多余字符）</td> 
  </tr> 
  <tr style=""> 
   <td style="">%20.30c</td> 
   <td style="">（若名字空间长度小于20，则左边用空格填充；若名字空间长度超过30，截去多余字符）</td> 
  </tr> 
  <tr style=""> 
   <td style="">%-20.30c</td> 
   <td style="">（若名字空间长度小于20，则右边用空格填充；若名字空间长度超过30，截去多余字符）</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %C 
    </div> </td> 
   <td style="">列出调用logger的类的全名（包含包路径）</td> 
   <td colspan="2" style="">假设当前类是"org.apache.xyz.SomeClass"</td> 
  </tr> 
  <tr style=""> 
   <td style="">%C</td> 
   <td style="">org.apache.xyz.SomeClass</td> 
  </tr> 
  <tr style=""> 
   <td style="">%C{1}</td> 
   <td style="">SomeClass</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %d 
    </div> </td> 
   <td style="">显示日志记录时间，{&lt;日期格式&gt;}使用ISO8601定义的日期格式</td> 
   <td style="">%d{yyyy/MM/dd HH:mm:ss,SSS}</td> 
   <td style="">2005/10/12 22:23:30,117</td> 
  </tr> 
  <tr style=""> 
   <td style="">%d{ABSOLUTE}</td> 
   <td style="">22:23:30,117</td> 
  </tr> 
  <tr style=""> 
   <td style="">%d{DATE}</td> 
   <td style="">12 Oct 2005 22:23:30,117</td> 
  </tr> 
  <tr style=""> 
   <td style="">%d{ISO8601}</td> 
   <td style="">2005-10-12 22:23:30,117</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %F 
    </div> </td> 
   <td style="">显示调用logger的源文件名</td> 
   <td style="">%F</td> 
   <td style="">MyClass.java</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %l 
    </div> </td> 
   <td style="">输出日志事件的发生位置，包括类目名、发生的线程，以及在代码中的行数</td> 
   <td style="">%l</td> 
   <td style="">MyClass.main(MyClass.java:129)</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %L 
    </div> </td> 
   <td style="">显示调用logger的代码行</td> 
   <td style="">%L</td> 
   <td style="">129</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %m 
    </div> </td> 
   <td style="">显示输出消息</td> 
   <td style="">%m</td> 
   <td style="">This is a message for debug.</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %M 
    </div> </td> 
   <td style="">显示调用logger的方法名</td> 
   <td style="">%M</td> 
   <td style="">main</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %n 
    </div> </td> 
   <td style="">当前平台下的换行符</td> 
   <td style="">%n</td> 
   <td style="">Windows平台下表示rn<br style=""> UNIX平台下表示n</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %p 
    </div> </td> 
   <td style="">显示该条日志的优先级</td> 
   <td style="">%p</td> 
   <td style="">INFO</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %r 
    </div> </td> 
   <td style="">显示从程序启动时到记录该条日志时已经经过的毫秒数</td> 
   <td style="">%r</td> 
   <td style="">1215</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %t 
    </div> </td> 
   <td style="">输出产生该日志事件的线程名</td> 
   <td style="">%t</td> 
   <td style="">MyClass</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %x 
    </div> </td> 
   <td style="">按NDC（Nested Diagnostic Context，线程堆栈）顺序输出日志</td> 
   <td colspan="2" style="">假设某程序调用顺序是MyApp调用com.foo.Bar</td> 
  </tr> 
  <tr style=""> 
   <td style="">%c %x - %m%n</td> 
   <td style="">MyApp - Call com.foo.Bar.<br style=""> com.foo.Bar - Log in Bar<br style=""> MyApp - Return to MyApp.</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %X 
    </div> </td> 
   <td style="">按MDC（Mapped Diagnostic Context，线程映射表）输出日志。通常用于多个客户端连接同一台服务器，方便服务器区分是那个客户端访问留下来的日志。</td> 
   <td style="">%X{5}</td> 
   <td style="">（记录代号为5的客户端的日志）</td> 
  </tr> 
  <tr style=""> 
   <td style=""> 
    <div style="margin:0px; padding:0px">
      %% 
    </div> </td> 
   <td style="">显示一个百分号</td> 
   <td style="">%%</td> 
   <td style="">%</td> 
  </tr> 
 </tbody> 
</table>

列了这么多，举几个实际的例子吧，比如log4j.properties的内容为：

<table style="border-collapse:collapse; border-spacing:0px; max-width:100%; background-color:transparent"> 
 <tbody style=""> 
  <tr style=""> 
   <td style="">#log4j config<br style=""> log4j.rootLogger=DEBUG,OUTPUT<br style=""> <br style=""> log4j.appender.OUTPUT.layout=org.apache.log4j.PatternLayout<br style=""> log4j.appender.OUTPUT.layout.ConversionPattern=%d{DATE} %-4r [%t] %-5p %c %x - %m%n<br style=""> ……</td> 
  </tr> 
 </tbody> 
</table>

那么一个可能的输出是：

12 Oct 2005 22:23:30,117 0 \[main\] INFO MyApp - Entering application.  
……   
12 Oct 2005 22:23:30,162 45 \[main\] INFO MyApp - Exiting application.

摘自：[http://blog.gceclub.sun.com.cn/index.php?op=ViewArticle&articleId=734&blogId=6][http_blog.gceclub.sun.com.cn_index.php_op_ViewArticle_articleId_734_blogId_6]

[http_logging.apache.org_log4j_docs_api_org_apache_log4j_PatternLayout.html]: http://logging.apache.org/log4j/docs/api/org/apache/log4j/PatternLayout.html
[http_blog.gceclub.sun.com.cn_index.php_op_ViewArticle_articleId_734_blogId_6]: http://blog.gceclub.sun.com.cn/index.php?op=ViewArticle&articleId=734&blogId=6