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Posted to log4j-user@logging.apache.org by Ari King <ar...@gmail.com> on 2010/11/23 14:48:45 UTC

Help understanding Log4j basics

I'd appreciate help in clarifying the following:

1. How does one start log4j in a webapp? Is having the
log4j.properties or log4j.xml file in the classpath enough?
2. How does one stop log4j in a webapp?
3. Is there a way to specify which level of logging, i.e. debug, info,
error, is printed?

Thanks.

-Ari

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RE: Help understanding Log4j basics

Posted by Bender Heri <hb...@ergonomics.ch>.
> I've previously searched the manual and I understand the hierarchy of:
> DEBUG < INFO < WARN < ERROR < FATAL
> However, I'm interested in in learning if there is a way to print ONLY
> one level rather than the target level and all levels above it. Unless
> I've missed it, the manual does not explain if this is possible (or
> how to do it).

In order to print a particular level only you can use LevelFilters which you can configure in xml configuration. E.g.

    <appender name="CONSOLE.OUT" class="org.apache.log4j.ConsoleAppender">
        <param name="target" value="System.out"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{HH:mm:ss.SSS} (%6r) %-5p [%-7t] %F:%L %x - %m%n"/>
        </layout>
        <filter class="org.apache.log4j.varia.LevelRangeFilter">
            <param name="LevelMin" value="trace"/>
            <param name="LevelMax" value="info"/>
            <param name="AcceptOnMatch" value="false"/>
        </filter>
    </appender>


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Re: Help understanding Log4j basics

Posted by Ari King <ar...@gmail.com>.
>> 2. How does one stop log4j in a webapp?
>
> Configure it via log4j config, then restart webapp (this reloads configuration)

After reviewing the manual, as I understand it the way to turn "off"
logging is by not assigning a log level or assigning a high (error or
fatal) log level. But doesn't that leave open the possibility of
having log messages, albeit of a higher level i.e. error or fatal?

>> 3. Is there a way to specify which level of logging, i.e. debug, info,
>> error, is printed?
>
> Yes, via the log4j configuration file.
> http://logging.apache.org/log4j/1.2/manual.html
> (search for configuration)

I've previously searched the manual and I understand the hierarchy of:
DEBUG < INFO < WARN < ERROR < FATAL
However, I'm interested in in learning if there is a way to print ONLY
one level rather than the target level and all levels above it. Unless
I've missed it, the manual does not explain if this is possible (or
how to do it).

Best,
Ari

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Re: Help understanding Log4j basics

Posted by Christian Grobmeier <gr...@gmail.com>.
> 1. How does one start log4j in a webapp? Is having the
> log4j.properties or log4j.xml file in the classpath enough?

Usually yes. You should have log4j itself in the classpath, of course.

> 2. How does one stop log4j in a webapp?

Configure it via log4j config, then restart webapp (this reloads configuration)

> 3. Is there a way to specify which level of logging, i.e. debug, info,
> error, is printed?

Yes, via the log4j configuration file.
http://logging.apache.org/log4j/1.2/manual.html
(search for configuration)

Cheers,
Christian

>
> Thanks.
>
> -Ari
>
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> To unsubscribe, e-mail: log4j-user-unsubscribe@logging.apache.org
> For additional commands, e-mail: log4j-user-help@logging.apache.org
>
>



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