Note that log4j will only invoke this logic if the application has a lookup of
the form ${main:<argnum>} in its configuration.
In environments without JMX the app may even need to explicitly initialize the
main arguments map.
This doesn't happen without being requested by the app, so I don't share the
concern.
Sent from my iPhone
> On 2014/08/08, at 16:54, Mikael Ståldal <[email protected]>
> wrote:
>
> To me, it seems conceptually wrong for a library (like Log4j) to read
> command line arguments behind the scenes without involvement from the
> application. Command line arguments are for the application to parse.
>
> System properties is the proper way to configure a library without
> involvement from the application
>
>
>> On Thu, Aug 7, 2014 at 7:02 PM, Gary Gregory <[email protected]> wrote:
>>
>> Please see this experiment:
>> https://issues.apache.org/jira/browse/LOG4J2-771
>>
>> Gary
>>
>>
>> On Thu, Aug 7, 2014 at 7:57 AM, Gary Gregory <[email protected]>
>> wrote:
>>
>>> On an Oracle JVM, you use a system property lookup to get the
>>> "sun.java.command" system property which gives you the whole command line
>>> but we do not have a syntax to parse it...
>>>
>>> Gary
>>>
>>>
>>> On Thu, Aug 7, 2014 at 2:27 AM, Gary Gregory <[email protected]>
>>> wrote:
>>>
>>>> It'll be more complicated than just grabbing the main args of course.
>>>>
>>>> If I say something like ${main:0} that seems easy to deal with, but when
>>>> I say ${main:--file} or ${main:-f} or ${main:-file}, that should pickup
>> the
>>>> _next_ arg in the array. What if it is missing or the next arg is
>> another
>>>> dash option? Too bad I guess. What are the rules?
>>>>
>>>> I could see two lookup classes:
>>>> - One is a named Map Lookup built from a String[], which would be a
>>>> singleton called by the main method:
>>>> MainArgumentsLookup.SINGELTON.set(args); Is the args array a reference
>> or a
>>>> deep copy?
>>>> - Another is the more complex and vendor dependent (and unproven) stack
>>>> walker.
>>>>
>>>> Gary
>>>>
>>>>
>>>>> On Wed, Aug 6, 2014 at 11:45 PM, Matt Sicker <[email protected]> wrote:
>>>>>
>>>>> Hey, it's better than having to use sun.util.Reflection!
>>>>>
>>>>>
>>>>>> On 6 August 2014 20:19, Gary Gregory <[email protected]> wrote:
>>>>>>
>>>>>> And worse: vendor specific!
>>>>>>
>>>>>> Gary
>>>>>>
>>>>>>
>>>>>>> On Wed, Aug 6, 2014 at 9:05 PM, Remko Popma <[email protected]>
>>>>>> wrote:
>>>>>>
>>>>>>> Oooh... A little naughty, but a lot of fun! :-)
>>>>>>> Thanks for the pointer!
>>>>>>>
>>>>>>> Sent from my iPhone
>>>>>>>
>>>>>>>> On 2014/08/07, at 9:44, Gary Gregory <[email protected]>
>>>>> wrote:
>>>>>>>>
>>>>>>>> With some debug API hackery:
>> http://docs.oracle.com/javase/7/docs/jdk/api/jpda/jdi/com/sun/jdi/StackFrame.html
>>>>>>>>
>>>>>>>> Gary
>>>>>>>>
>>>>>>>>
>>>>>>>>> On Wed, Aug 6, 2014 at 8:36 PM, Remko Popma <
>>>>> [email protected]>
>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>> I don't follow... If you walk the stack trace you can find the
>>>>> name of
>>>>>>> the
>>>>>>>>> original class whose main() method was called, but how would
>> that
>>>>> give
>>>>>>> you
>>>>>>>>> access to the main method's parameter values?
>>>>>>>>>
>>>>>>>>> Sent from my iPhone
>>>>>>>>>
>>>>>>>>>> On 2014/08/07, at 9:26, Gary Gregory <[email protected]>
>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>> Yes you are right but the stack walker could be used even if
>> you
>>>>> do
>>>>>> not
>>>>>>>>> control to source for main. Maybe a script calls a main and then
>>>>> my
>>>>>> app
>>>>>>>>> plugin gets called and I want to also follow the verbose command
>>>>> line
>>>>>>>>> setting.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Gary
>>>>>>>>>>
>>>>>>>>>> <div>-------- Original message --------</div><div>From: Ralph
>>>>> Goers <
>>>>>>>>> [email protected]> </div><div>Date:08/06/2014 19:18
>>>>>>>>> (GMT-05:00) </div><div>To: Log4J Users List <
>>>>>>>>> [email protected]> </div><div>Subject: Re: Set the
>>>>> file
>>>>>>> name
>>>>>>>>> based on command line args </div><div>
>>>>>>>>>> </div>Wouldn’t it be easier to have a Lookup that your main
>>>>> called
>>>>>> and
>>>>>>>>> just passed the arguments? But yeah, it should be possible to
>> do
>>>>> what
>>>>>>> you
>>>>>>>>> are suggesting.
>>>>>>>>>>
>>>>>>>>>> Ralph
>>>>>>>>>>
>>>>>>>>>>> On Aug 6, 2014, at 4:09 PM, Gary Gregory <
>>>>> [email protected]>
>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>> I wonder if we could write a "MainArgumentsLookup" that finds
>>>>> the
>>>>>> main
>>>>>>>>>>> thread and walks up the stack to the public static
>>>>> main(String[])
>>>>>> main
>>>>>>>>>>> methods and gets the arguments from the stack...
>>>>>>>>>>>
>>>>>>>>>>> Gary
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Wed, Aug 6, 2014 at 6:54 PM, Ralph Goers <
>>>>>>> [email protected]
>>>>>>>>>>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Well….
>>>>>>>>>>>>
>>>>>>>>>>>> You would really be passing the name of the file to the
>>>>> Appender,
>>>>>>> not a
>>>>>>>>>>>> Logger. Loggers only reference Appenders so you can’t really
>>>>>>> configure
>>>>>>>>>>>> them with Appender configuration data. That said, Log4j 2
>>>>> provides
>>>>>> a
>>>>>>>>> few
>>>>>>>>>>>> ways you could do this:
>>>>>>>>>>>> 1. Set a system property and reference it via
>>>>> ${sys:propertyName}
>>>>>> in
>>>>>>>>> the
>>>>>>>>>>>> configuration. The manual has examples of this.
>>>>>>>>>>>> 2. Create a custom Lookup Plugin and then register the file
>>>>> name
>>>>>> with
>>>>>>>>> the
>>>>>>>>>>>> Lookup. Then reference it from the configuration as
>>>>> ${myLookup:
>>>>>>> key}
>>>>>>>>>>>> where myLookup is the name of your custom Lookup and key is
>> the
>>>>>> name
>>>>>>>>> that
>>>>>>>>>>>> represents the file name value.
>>>>>>>>>>>> 3. Create a custom Configuration the extends XMLConfiguration
>>>>> or
>>>>>>>>>>>> JSONConfiguration. Pass the file name to that class and have
>>>>> it add
>>>>>>>>> that as
>>>>>>>>>>>> a property to the properties Map in the configuration. The
>> XML
>>>>>> could
>>>>>>>>> then
>>>>>>>>>>>> just reference it as ${propertyName}.
>>>>>>>>>>>>
>>>>>>>>>>>> Ralph
>>>>>>>>>>>>
>>>>>>>>>>>>> On Aug 6, 2014, at 2:03 PM, Arwen Pond <[email protected]>
>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>> My application takes a parameter where the user can specify
>>>>> the
>>>>>> log
>>>>>>>>>>>> file. I'd like to pass this parameter to the Logger which
>>>>> uses a
>>>>>>>>>>>> FileAppender. I am not sure how to do this in log4j 2.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>> Arwen
>>>>>>>>>>>>>
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>>>>>>>>>>> --
>>>>>>>>>>> E-Mail: [email protected] | [email protected]
>>>>>>>>>>> Java Persistence with Hibernate, Second Edition
>>>>>>>>>>> <http://www.manning.com/bauer3/>
>>>>>>>>>>> JUnit in Action, Second Edition <
>>>>> http://www.manning.com/tahchiev/>
>>>>>>>>>>> Spring Batch in Action <http://www.manning.com/templier/>
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>>>>>>>>> For additional commands, e-mail:
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>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> E-Mail: [email protected] | [email protected]
>>>>>>>> Java Persistence with Hibernate, Second Edition
>>>>>>>> <http://www.manning.com/bauer3/>
>>>>>>>> JUnit in Action, Second Edition <
>> http://www.manning.com/tahchiev/>
>>>>>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>>>>>> Blog: http://garygregory.wordpress.com
>>>>>>>> Home: http://garygregory.com/
>>>>>>>> Tweet! http://twitter.com/GaryGregory
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>>>>>>> To unsubscribe, e-mail: [email protected]
>>>>>>> For additional commands, e-mail:
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>>>>>>
>>>>>>
>>>>>> --
>>>>>> E-Mail: [email protected] | [email protected]
>>>>>> Java Persistence with Hibernate, Second Edition
>>>>>> <http://www.manning.com/bauer3/>
>>>>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>>>> Blog: http://garygregory.wordpress.com
>>>>>> Home: http://garygregory.com/
>>>>>> Tweet! http://twitter.com/GaryGregory
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Matt Sicker <[email protected]>
>>>>
>>>>
>>>>
>>>> --
>>>> E-Mail: [email protected] | [email protected]
>>>> Java Persistence with Hibernate, Second Edition
>>>> <http://www.manning.com/bauer3/>
>>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>>> Spring Batch in Action <http://www.manning.com/templier/>
>>>>
>>>> Blog: http://garygregory.wordpress.com
>>>> Home: http://garygregory.com/
>>>> Tweet! http://twitter.com/GaryGregory
>>>
>>>
>>>
>>> --
>>> E-Mail: [email protected] | [email protected]
>>> Java Persistence with Hibernate, Second Edition
>>> <http://www.manning.com/bauer3/>
>>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>>> Spring Batch in Action <http://www.manning.com/templier/>
>>> Blog: http://garygregory.wordpress.com
>>> Home: http://garygregory.com/
>>> Tweet! http://twitter.com/GaryGregory
>>
>>
>>
>> --
>> E-Mail: [email protected] | [email protected]
>> Java Persistence with Hibernate, Second Edition
>> <http://www.manning.com/bauer3/>
>> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
>> Spring Batch in Action <http://www.manning.com/templier/>
>> Blog: http://garygregory.wordpress.com
>> Home: http://garygregory.com/
>> Tweet! http://twitter.com/GaryGregory
>
>
>
> --
> Mikael Ståldal
> Chief Software Architect
> *Appear*
> Phone: +46 8 545 91 572
> Email: [email protected]
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