log4j2配置详解

据网上博客整理，再加上自己一些理解。
参考：
https://www.cnblogs.com/sa-dan/p/6837225.html
https://www.jianshu.com/p/d13c2e50a89c

<?xml version="1.0" encoding="UTF-8"?>
<!--日志级别以及优先级排序: OFF > FATAL > ERROR > WARN > INFO > DEBUG > TRACE > ALL -->
<!--status="WARN" :用于设置log4j2自身内部日志的信息输出级别，默认是OFF-->
<!--monitorInterval="30"  :间隔秒数,自动检测配置文件的变更和重新配置本身-->
<configuration status="warn" monitorInterval="60" strict="true">
  <properties>
	<!--自定义一些常量，之后使用${变量名}引用-->
    <property name="logpath">./logs</property>
    <property name="charset">UTF-8</property>
	<!--自定义的输出格式-->
    <property name="pattern">%-d{yyyy-MM-dd HH:mm:ss.SSS}@@%p@@%X{ip}@@%t %C@@%X{requestId} %M %m %n </property>
  </properties>
  <!--appenders:定义输出内容,输出格式,输出方式,日志保存策略等,常用其下三种标签[console,File,RollingFile]-->
  <!--Appender可以理解为日志的输出目的地-->
  <appenders>
    <!--console :控制台输出的配置-->
    <Console name="console" target="SYSTEM_OUT">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
    </Console>
	<!--RollingRandomAccessFile性能比RollingFile提升官网宣称是20-200%-->
    <RollingRandomAccessFile name="YZY.TRACE" immediateFlush="true" bufferSize="1024"
      fileName="${logpath}/trace.log"
      filePattern="${logpath}/trace.log.%d{yyyy-MM-dd}.gz">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="trace.log.*.gz"/>
          <IfLastModified age="3d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.SYSTEM" immediateFlush="true" bufferSize="4096"
      fileName="${logpath}/system.log"
      filePattern="${logpath}/system.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
	  <!--引用上面自定义的输出格式-->
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <Filters>
		<!--ThresholdFilter :日志输出过滤-->
        <!--level="info" :日志级别,onMatch="ACCEPT" :级别在info之上则接受,onMismatch="DENY" :级别在info之下则拒绝-->
        <!--与logger、root中定义的日志级别相配合，相当于两个闸门，先判断logger、root的级别，符合了才会用到该filter中的level，此时再进行一次筛选-->
        <ThresholdFilter level="TRACE" onMatch="ACCEPT" onMismatch="DENY"/>
        <!--<ThresholdFilter level="DEBUG" onMatch="ACCEPT" onMismatch="DENY"/>-->
        <!--<ThresholdFilter level="INFO" onMatch="ACCEPT" onMismatch="DENY"/>-->
      </Filters>
	  <!-- Policies :日志滚动策略-->
      <Policies>
        <!--<TimeBasedTriggeringPolicy interval="1" modulate="true"/>-->
        <CronTriggeringPolicy schedule="0 0 2 * * ?" evaluateOnStartup="true"/>
      </Policies>
	  <!-- DefaultRolloverStrategy属性如不设置，则默认为最多同一文件夹下7个文件-->
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="system.log.*.gz"/>
	  <!--只保留7天，超过则删除-->
          <IfLastModified age="7d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.ERROR" immediateFlush="true" bufferSize="4096"
      fileName="${logpath}/error.log"
      filePattern="${logpath}/error.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <Filters>
        <ThresholdFilter level="ERROR" onMatch="ACCEPT" onMismatch="DENY"/>
      </Filters>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="error.log.*.gz"/>
          <IfLastModified age="7d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.AUDIT" immediateFlush="false" bufferSize="8192"
      fileName="${logpath}/audit.log"
      filePattern="${logpath}/audit.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <Filters>
        <ThresholdFilter level="WARN" onMatch="ACCEPT" onMismatch="DENY"/>
      </Filters>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="audit.log.*.gz"/>
          <IfLastModified age="7d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.POOL" immediateFlush="true" bufferSize="1024"
      fileName="${logpath}/pool.log"
      filePattern="${logpath}/pool.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="pool.log.*.gz"/>
          <IfLastModified age="3d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.MONITOR" immediateFlush="true" bufferSize="1024"
      fileName="${logpath}/monitor.log"
      filePattern="${logpath}/pool.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="pool.log.*.gz"/>
          <IfLastModified age="3d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
    <RollingRandomAccessFile name="YZY.BIZ" immediateFlush="true"
      fileName="${logpath}/biz.log"
      filePattern="${logpath}/biz.log.%d{yyyy-MM-dd}.gz"
      ignoreExceptions="false">
      <PatternLayout pattern="${pattern}" charset="${charset}"/>
      <TimeBasedTriggeringPolicy/>
      <DefaultRolloverStrategy>
        <Delete basePath="${logpath}" maxDepth="2" followLinks="true">
          <IfFileName glob="biz.log.*.gz"/>
          <IfLastModified age="7d"/>
        </Delete>
      </DefaultRolloverStrategy>
    </RollingRandomAccessFile>
  </appenders>
  
  <!--然后定义logger，只有定义了logger并引入的appender，appender才会生效-->
  <loggers>
	<!--additivity="false"表示在该logger中输出的日志不会再延伸到父层logger。这里如果改为true，则会延伸到Root Logger，遵循Root Logger的配置也输出一次。-->
    <Logger additivity="false" name="YZY.TRACE" level="INFO">
      <AppenderRef ref="YZY.TRACE"/>
    </Logger>
    <Logger additivity="false" name="YZY.SYSTEM" level="INFO">
      <AppenderRef ref="YZY.SYSTEM"/>
      <AppenderRef ref="YZY.ERROR"/>
    </Logger>
    <Logger additivity="false" name="YZY.BIZ" level="INFO">
      <AppenderRef ref="YZY.BIZ"/>
    </Logger>
    <!--Logger节点用来单独指定日志的形式，name为包路径,比如要为org.apache包下所有日志指定为INFO级别等。 -->
    <Logger additivity="false" name="org.apache" level="INFO">
      <AppenderRef ref="console"/>
    </Logger>
    <Logger additivity="false"
      name="com.alibaba.dubbo.common.threadpool.monitor.MonitorPoolRunnable" level="INFO">
      <AppenderRef ref="YZY.POOL"/>
    </Logger>
    <Logger additivity="false" name="com.alibaba.dubbo.monitor.dubbo.sfextend.SfMonitorExtend"
      level="INFO">
      <AppenderRef ref="YZY.MONITOR"/>
    </Logger>
    <!--针对,request以及reponse的信息配置输出级别,生产线请配置为error-->
    <Logger additivity="true" name="com.alibaba.dubbo.rpc.protocol.rest.support" level="INFO">
      <AppenderRef ref="console"/>
    </Logger>
    <!-- 在开发和测试环境启用,输出sql -->
    <Logger additivity="true" name="com.YZY.mapper" level="DEBUG">
    </Logger>
	<!-- Root节点用来指定项目的根日志，如果没有单独指定Logger，那么就会默认使用该Root日志输出 -->
    <Root level="DEBUG" includeLocation="true">
      <AppenderRef ref="console"/>
      <AppenderRef ref="YZY.SYSTEM"/>
      <AppenderRef ref="YZY.ERROR"/>
      <AppenderRef ref="YZY.AUDIT"/>
    </Root>
  </loggers>
</configuration>

public class TestLog {

    public static void main(String[] args) {

        Logger logger = LoggerFactory.getLogger("YZY.SYSTEM");
        //Logger logger = LoggerFactory.getLogger(TestLog.class);

        logger.trace("trace level");
        logger.debug("debug level");
        logger.info("info level");
        logger.warn("warn level");
        logger.error("error level");
    }
}

RollingRandomAccessFile性能比RollingFile提高很多。
另https://www.cnblogs.com/sa-dan/p/6837225.html解释了 name属性的用法。
即可以在程序中使用Logger logger = LoggerFactory.getLogger("YZY.SYSTEM");来获取对应的logger，如果找到对应名称的logger，就不会使用root节点的logger。
LoggerFactory.getLogger(TestLog.class)底层实现也是调用的getLogger(clazz.getName());
如上代码，LoggerFactory.getLogger(TestLog.class)找不到对应的logger，会使用默认的root节点的配置。