此节分享xml形式的log4j.properties。

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1. 将日志输出到控制台

log4j.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

    <appender name="console" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
        </layout>
    </appender>

    <root>
        <level value="DEBUG" />
        <appender-ref ref="console" />
    </root>

</log4j:configuration>

2. 将日志记录到文件中

log4j.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

    <appender name="file" class="org.apache.log4j.RollingFileAppender">
       <param name="append" value="false" />
       <param name="maxFileSize" value="10KB" />
       <param name="maxBackupIndex" value="5" />
       <!-- For Tomcat -->
       <param name="file" value="${catalina.home}/logs/myStruts1App.log" />
       <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
       </layout>
    </appender>

    <root>
        <level value="ERROR" />
        <appender-ref ref="file" />
    </root>

</log4j:configuration>

3. 将日志输出到控制台同时记录到文件中

log4j.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

    <appender name="console" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
        </layout>
    </appender>

    <appender name="file" class="org.apache.log4j.RollingFileAppender">
        <param name="append" value="false" />
        <param name="maxFileSize" value="10MB" />
        <param name="maxBackupIndex" value="10" />
        <param name="file" value="${catalina.home}/logs/myStruts1App.log" />
        <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
        </layout>
    </appender>

    <root>
        <level value="DEBUG" />
        <appender-ref ref="console" />
        <appender-ref ref="file" />
    </root>

</log4j:configuration>

参考资料：

• Log4j 1.2指南
• Log4j布局模式配置文档
• log4j.properties