jakarta commons log4j 学习笔记

关键字：jakarta, commons, configuration

如何配置Log4j

1. 用BasicConfigurator 对Log4j 进行配置，入门级的配置方式：

   import org.apache.log4j.BasicConfigurator;
   import org.apache.log4j.Logger;
   ......
   public class Log4jTest {
     private static Logger logger = Logger.getLogger(Log4jTest.class.getName());
   ......
     public static void main(String[] args) {
       BasicConfigurator.configure();
       logger.info("log4j has been configurated with BasicConfigurator.configuration successfully!");
     }
   }

   运行后可以得到类似于下面的结果：

   0 [main] INFO Log4jTest - log4j has been configed with BasicConfigurator.configure() successfully!

   
   
2. 用配置文件对Log4j 进行配置，非常灵活的一种方式：

   # For the general syntax of property based configuration files see the
   # documenation of org.apache.log4j.PropertyConfigurator.
   # The root category uses the appender called A1. Since no priority is
   # specified, the root category assumes the default priority for root
   # which is DEBUG in log4j. The root category is the only category that
   # has a default priority. All other categories need not be assigned a
   # priority in which case they inherit their priority from the
   # hierarchy.

   log4j.rootCategory=INFO, A1, A2

   # A1 is set to be a FileAppender which outputs to the file
   # "factor.log". Start the server NumberCruncherServer and two
   # NumberCruncherClients, and ask to factor two numbers
   # near-simultaneously. Notice that the log output from these two
   # requests are logged in the file factor.log. Nevertheless, the logs
   # of these requests can still be distinguished given their distinct
   # nested diagnostic contexts.

   log4j.appender.A1=org.apache.log4j.DailyRollingFileAppender
   log4j.appender.A1.File=WEB-INF/logs/portal.log
   log4j.appender.A1.DatePattern='.'yyyy-MM-dd
   log4j.appender.A1.layout=org.apache.log4j.PatternLayout

   log4j.appender.A2=org.apache.log4j.ConsoleAppender
   log4j.appender.A2.layout=org.apache.log4j.PatternLayout

   # Note the %x conversion specifier for NDC printing.
   # %d date time
   # %-5p debug level
   # %m messages
   # %l class with method and line number (slowly! dubug only, on release use %c{2} in release version)
   # %n \n or \r\n

   #debug version
   log4j.appender.A1.layout.ConversionPattern=%d [%-5p] %l - %m%n
   log4j.appender.A2.layout.ConversionPattern=%d [%-5p] %l - %m%n

   #release version
   # log4j.appender.A1.layout.ConversionPattern=%d [%-5p] %c{2} - %m%n

   
   有了上面的配置文件后，可以通过以下任意一种方式对其进行装载：
   • 让Log4j自动装载配置文件
     将上面的文件命名为log4j.properties，并保存到WEB-INF/classes/ 目录下，这样当第一次调用Logger.getLogger(SomeClass.class.getName()); 时，Log4j 就会自动装载该配置文件对log 系统进行初始化。
   • 用系统变量指定配置文件的位置
     如果不想把配置文件放到WEB-INF/clases/ 目录下，或者不想把配置文件命名为log4j.properties 那么就可以通过系统变量log4j.configuration来对其进行自定义，例如：
     -Dlog4j.configuration=file:/D:/projects/someproject/WEB-INF/log4j.properties
     用指定位置的文件进行配置
     -Dlog4j.configuration=foo.txt
     用WEB-INF/classes/目录下的foo.txt 进行配置
     
   • 用PropertyConfigurator 读取配置文件

     import org.apache.log4j.PropertyConfigurator;
     import org.apache.log4j.Logger;
     ......
     public class Log4jTestServlet {
       private static Logger logger = Logger.getLogger(Log4jTestServlet.class.getName());
     ......
       public void init(ServletConfig servletConfig) throws ServletException {
         super.init(servletConfig);
         String file = getRealPath(getInitParameter("log4j-init-file"));
         PropertyConfigurator.configure(file);
         /*
          *PropertyConfigurator.configure(Properties);
          *PropertyConfigurator.configure(URL);
          *PropertyConfigurator.configureAndWatch(file, 30); //delay 30 second
          */
         logger.info("log4j has been configurated with PropertyConfigurator.configuration successfully!");
       }
     }

参考文档

Log4j short mannul
http://logging.apache.org/log4j/docs/manual.html