log4j2.xml总共分为三大块：Properties，Appenders，Loggers.

<?xml version="1.0" encoding="UTF-8"?>
<configuration monitorInterval="30" shutdownHook="disable">
    <Properties>
        <Property name="baseDir">../log</Property>
        <Property name="impLogFileName">../log/imp.log</Property
        <Property name="moErrorLogFileName">../log/moError.log</Property>
        <Property name="impLogDeleteGlob">*/imp-*.log.gz</Property>
        <Property name="moErrorDeleteGlob">*/moError-*.log.gz</Property>
        <Property name="moErrorLogFilePatten">../log/%d{yyyy-MM}/moError-%d{MM-dd-yyyy_HH.mm.ss}.log.gz</Property>
    </Properties>
/*如上 Property 定义log文件名，包含相对路径*/
/*如下 Appenders 定义了 Property 中各个log文件的打印规范和限制*/
<Appenders>
        <Console name="stdout" target="System.out">
            <PatternLayout pattern="%d{ISO8601} %sn [%t] %-5p %c - %m%n"/>
        </Console>
        <RollingRandomAccessFile name="impLogFileAppender" fileName="${impLogFileName}"
                                 filePattern="${impLogFilePatten}" immediateFlush="false">
            <PatternLayout pattern="${impLogLayout}"/>
            <SizeBasedTriggeringPolicy size="100MB"/>
            <DefaultRolloverStrategy>    /*超过限制要被删掉的文件*/
                <Delete basePath="${baseDir}" maxDepth="2">
                    <IfFileName glob="${impLogDeleteGlob}">
                        <IfAccumulatedFileCount exceeds="30"/>
                    </IfFileName>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingRandomAccessFile>
        <RollingRandomAccessFile name="moErrorLogFileAppender" fileName="${moErrorLogFileName}"
                                 filePattern="${impLogFilePatten}" immediateFlush="false">
            <PatternLayout pattern="${impLogLayout}"/>
/*<=ERROR级别的log受到filter的限制，平均每秒打印 <10,排队数量不超过100*/
            <BurstFilter level="ERROR" rate="10" maxBurst="100"/>
            <SizeBasedTriggeringPolicy size="100MB"/>  //一个文件超过 100M 就产生一个 gz
            <DefaultRolloverStrategy>
                <Delete basePath="${baseDir}" maxDepth="2">
                    <IfFileName glob="${moErrorDeleteGlob}">
                        <IfAccumulatedFileCount exceeds="30"/>  // gz 文件超过30个就覆盖
                    </IfFileName>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingRandomAccessFile>
    </Appenders>
/*以下 Loggers 定义了工程代码中的log输出到哪些文件*/
    <Loggers>
        <AsyncLogger name="com.nokia.imp.conversion.impl.domains.ParameterConverter" level="ERROR" additivity="false">
            <AppenderRef ref="moErrorLogFileAppender" />
        </AsyncLogger>
        <root level="INFO"> /*未定义的默认输出到 root定义中的 appender*/
            <appender-ref ref="impLogFileAppender"/>
            <appender-ref ref="errorAppender"/>
        </root>
    </Loggers>