Log4j 2.0 使用说明(2) 配置文件

在这里我们试着添加配置文件。

另外，我们需要注意的是2.0版本中的配置只能为Xml和Json。

测试代码为：

package com.foo;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Bar {

	static Logger logger = LogManager.getLogger(Bar.class.getName());

    public boolean doIt() {
      logger.entry();   //Log entry to a method
      logger.error("Did it again!");   //Log a message object with the ERROR level
      logger.exit();    //Log exit from a method 
      return false;
    }
}

import com.foo.Bar;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class MyApp {

	   // Define a static logger variable so that it references the
	   // Logger instance named "MyApp".
	   private static Logger logger = LogManager.getLogger(MyApp.class.getName());

	   public static void main(String[] args) {

	   // Set up a simple configuration that logs on the console.

		   logger.trace("Entering application.");  //Log a message object with the TRACE level.
		   Bar bar = new Bar();
		   if (!bar.doIt()) {
			   logger.error("Didn't do it.");
		   }
	  	   logger.trace("Exiting application.");
	   }
}

没有配置文件情况下的输出为：

17:13:01.540 [main] ERROR com.foo.Bar - Did it again!
17:13:01.540 [main] ERROR MyApp - Didn't do it.

由之前的例子我们不难知道，这是因为缺省配置文件的优先级默认为Error的缘故。

下面的配置文件在效果上等于缺省情况的下的配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </appenders>
  <loggers>
    <root level="error">
      <appender-ref ref="Console"/>
    </root>
  </loggers>
</configuration>

我们对上面的配置文件修改之后，再运行程序：

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </appenders>
  <loggers>
    <root level="trace">
      <appender-ref ref="Console"/>
    </root>
  </loggers>
</configuration>

输出结果为：

11:43:57.703 [main] TRACE edu.hrbeu.tested.MyApp - Entering application.
11:43:57.718 [main] TRACE com.foo.Bar -  entry
11:43:57.718 [main] ERROR com.foo.Bar - Did it again!
11:43:57.718 [main] TRACE com.foo.Bar -  exit
11:43:57.718 [main] ERROR edu.hrbeu.tested.MyApp - Didn't do it.
11:43:57.718 [main] TRACE edu.hrbeu.tested.MyApp - Exiting application.

将优先级设置为trace后就可以显式的跟踪程序的执行过程。

若是我们想去掉除com.foo.Bar以外所有的trace输出，我们可以增加一个新的注册事件，如下所示

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </appenders>
  <loggers>
    <logger name="com.foo.Bar" level="trace" additivity="false">
      <appender-ref ref="Console"/>
    </logger>
    <root level="error">
      <appender-ref ref="Console"/>
    </root>
  </loggers>
</configuration>

程序输出为：

11:53:31.796 [main] TRACE com.foo.Bar -  entry
11:53:31.796 [main] ERROR com.foo.Bar - Did it again!
11:53:31.796 [main] TRACE com.foo.Bar -  exit
11:53:31.796 [main] ERROR edu.hrbeu.tested.MyApp - Didn't do it.