How do I configure logging levels in log4j using XML?

How do I configure logging levels in log4j using XML?

To configure logging levels in log4j using XML, you need to define the loggers and their levels in the log4j.xml file.

Can you show me an example of a log4j.xml configuration?

Sure! Here's a simple example:

<log4j:configuration 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{ISO8601} %p %c{1} - %m%n" />
        </layout>
    </appender>
    <logger name="com.example">
        <level value="DEBUG" />
    </logger>
    <root>
        <level value="INFO" />
        <appender-ref ref="console" />
    </root>
</log4j:configuration>

What do the different logging levels like DEBUG and INFO mean?

DEBUG is used for detailed information, typically of interest only when diagnosing problems. INFO is used to highlight the progress of the application at a coarse-grained level.

Can I change the logging level at runtime?

Yes, you can change the logging level at runtime using the Logger.getLogger() method and calling setLevel() on the logger instance.