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−Title: Log4j and logger additivity
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−Date: 2008-02-18
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−Tags: log4j, logging
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−Lang: en
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−Sometimes you want to write more than one logfile using logj4. This is possible by defining multiple appenders and specifying an appender for a certain logger like this:
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−
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−    log4j.appender.A1=org.apache.log4j.ConsoleAppender
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−    ....
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−    log4j.appender.A2=org.apache.log4j.FileAppender
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−    ....
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−
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−    log4j.rootLogger=DEBUG, A1
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−    log4j.logger.foo=DEBUG, A2
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−Unfortunately, all output that goes through the logger foo comes out in both appenders, which may not be what you want. The log4j docs talk about *logger additivity* but don't show concrete examples how to configure it. The trick is to configure the additivity **on the logger** and **not on the appender**. (I always fall into that trap). Simply add the following to the example above to stop messages to logger foo come out on A1:
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−
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−    log4j.additivity.foo = false