快速将log4j.xml 转换为 logback.xml

应用的日志输出频率太高，log4j同步日志输出的时候锁竞争太过激烈，导致业务线程阻塞。系统load 200+，线程数2000+ 。所以想通过切换到logback 来提升日志输出的内容。

想要切换到logback要做两件事情：

* 切换pom中依赖的jar包 * 将log4j.xml 转换成 logback.xml 

第一件事情比较简单，但是第二件事情稍微有些麻烦，特别是碰到原本日志Appender就非常多的情况下（我们配置了超过50个Appender）一个一个手动改就很繁琐了。在网上找了很多都是从 log4j.properties 转换为 logback.xml 的，我们这边还是很少有用到log4j.properties的。 在Google 上找了好久找到了一个文章 http://rpuchkovskiy.blogspot.com/2014/11/xslt-to-convert-log4jxml-config-to.html。通过他可以把 log4j.xml 转换为 logback.xml ，不过他的实现比较老，我结合我们的使用场景稍微修改了下。

<!-- This XLST script converts log4j.xml.bak file to logback.xml file trying to mimic its behavior as close as possible @author Roman Puchkovskiy --> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" exclude-result-prefixes="log4j xalan" xmlns:log4j="http://jakarta.apache.org/log4j/" xmlns:xalan="http://xml.apache.org/xslt" xmlns:xslt="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" xalan:indent-amount="4"/> <xsl:variable name="vLower" select="'abcdefghijklmnopqrstuvwxyz'"/> <xsl:variable name="vUpper" select="'ABCDEFGHIJKLMNOPQRSTUVWXYZ'"/> <xsl:template match="/log4j:configuration"> <configuration> <xsl:apply-templates select="appender"/> <xsl:apply-templates select="logger"/> <xsl:apply-templates select="root"/> <xsl:apply-templates select="comment()"/> </configuration> </xsl:template> <xsl:template match="appender"> <appender> <xsl:attribute name="name"> <xsl:value-of select="@name"/> </xsl:attribute> <xsl:attribute name="class"> <xsl:choose> <!-- 定义了Appender 之间的映射关系 --> <xsl:when test="@class = 'org.apache.log4j.DailyRollingFileAppender'">ch.qos.logback.core.rolling.RollingFileAppender</xsl:when> <xsl:when test="@class = 'com.alibaba.common.logging.spi.log4j.DailyRollingFileAppender'">ch.qos.logback.core.rolling.RollingFileAppender</xsl:when> <xsl:when test="@class = 'org.apache.log4j.AsyncAppender'">ch.qos.logback.classic.AsyncAppender</xsl:when> <xsl:when test="@class = 'org.apache.log4j.ConsoleAppender'">ch.qos.logback.core.ConsoleAppender</xsl:when> <xsl:when test="@class = 'org.apache.log4j.net.SMTPAppender'">ch.qos.logback.classic.net.SMTPAppender</xsl:when> <xsl:when test="@class = 'org.apache.log4j.net.SocketAppender'">ch.qos.logback.classic.net.SocketAppender</xsl:when> <xsl:when test="@class = 'org.apache.log4j.net.SyslogAppender'">ch.qos.logback.classic.net.SyslogAppender</xsl:when> <xsl:otherwise> <xsl:message terminate="yes">Unknown appender class: <xsl:value-of select="@class"/> </xsl:message> </xsl:otherwise> </xsl:choose> </xsl:attribute> <xsl:apply-templates select="param"/> <xsl:apply-templates select="layout"/> <xsl:apply-templates select="filter"/> </appender> <xsl:call-template name="newline"/> </xsl:template> <xsl:template match="param"> <xsl:choose> <!-- 将log4j file 转换为 logback 的file --> <xsl:when test="@name = 'file'"> <xsl:element name="{concat(translate(substring(@name,1,1), $vUpper, $vLower),substring(@name, 2))}"> <xsl:value-of select="@value"/> </xsl:element> </xsl:when> </xsl:choose> </xsl:template> <xsl:template match="layout"> <xsl:choose> <!-- 将PatternLayout 做转换 --> <xsl:when test="@class = 'org.apache.log4j.PatternLayout'"> <xsl:choose> <xsl:when test="../@class = 'org.apache.log4j.ConsoleAppender' or ../@class = 'org.apache.log4j.DailyRollingFileAppender' or ../@class = 'com.alibaba.common.logging.spi.log4j.DailyRollingFileAppender'"> <encoder> <pattern> <xsl:value-of select="param[@name = 'ConversionPattern']/@value"/> </pattern> <charset>UTF-8</charset> </encoder> <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> <xsl:element name="fileNamePattern"> <xsl:value-of select="../param[@name = 'file']/@value" />.%d{yyyy-MM-dd}</xsl:element> <maxHistory>7</maxHistory> </rollingPolicy> </xsl:when> <xsl:when test="../@class = 'org.apache.log4j.net.SocketAppender' or ../@class = 'org.apache.log4j.net.SyslogAppender'"> <xsl:comment>this is NOT needed tor this logger, so it is commented out</xsl:comment> <xsl:comment><![CDATA[ <layout> <pattern>]]><xsl:value-of select="param[@name = 'ConversionPattern']/@value"/><![CDATA[</pattern> </layout>]]> </xsl:comment> </xsl:when> <xsl:otherwise> <layout> <pattern> <xsl:value-of select="param[@name = 'ConversionPattern']/@value"/> </pattern> </layout> </xsl:otherwise> </xsl:choose> </xsl:when> <xsl:otherwise> <xsl:message terminate="yes">Unknown layout class: <xsl:value-of select="@class"/> </xsl:message> </xsl:otherwise> </xsl:choose> </xsl:template> <xsl:template match="filter"> <xsl:choose> <xsl:when test="@class = 'org.apache.log4j.varia.LevelRangeFilter' and param[@name = 'LevelMin']/@value != '' and param[@name = 'LevelMax']/@value = 'FATAL'"> <filter class="ch.qos.logback.classic.filter.ThresholdFilter"> <level> <xsl:value-of select="param[@name = 'LevelMin']/@value"/> </level> </filter> </xsl:when> <xsl:otherwise> <xsl:message terminate="yes">Don't know what to do with filter</xsl:message> </xsl:otherwise> </xsl:choose> </xsl:template> <xsl:template match="logger"> <logger> <xsl:attribute name="name"> <xsl:value-of select="@name"/> </xsl:attribute> <xsl:attribute name="level"> <xsl:choose> <xsl:when test="level/@value = 'FATAL'">OFF</xsl:when> <xsl:otherwise> <xsl:value-of select="level/@value"/> </xsl:otherwise> </xsl:choose> </xsl:attribute> <xsl:if test="@additivity != ''"> <xsl:attribute name="additivity"> <xsl:value-of select="@additivity"/> </xsl:attribute> </xsl:if> <xsl:apply-templates select="appender-ref"/> </logger> </xsl:template> <xsl:template match="appender-ref"> <appender-ref> <xsl:attribute name="ref"> <xsl:value-of select="@ref"/> </xsl:attribute> </appender-ref> </xsl:template> <xsl:template match="root"> <xsl:call-template name="newline"/> <root> <xsl:attribute name="level"> <xsl:value-of select="level/@value"/> </xsl:attribute> <xsl:apply-templates select="appender-ref"/> <xsl:apply-templates select="comment()"/> </root> </xsl:template> <xsl:template match="comment()"> <xsl:copy-of select="."/> </xsl:template> <xsl:template name="newline"> <!-- don't reformat this! --> <xsl:text> </xsl:text> </xsl:template> </xsl:stylesheet>

使用方式很简单:

String[] parmas = {"-IN", "log4j.xml", "-XSL", "log4j-to-logback.xsl", "-OUT", "logback.xml"}; org.apache.xalan.xslt.Process.Process.main(parmas);