Re: No Virtual Destructor for LoggingEvent

Hi,

If this class is not meant for extension then why does Log4j doco say:
(1) "This class is of concern to those wishing to extend log4j."
Do they mean by that log4j developers rather than users - Sounds a bit bizarre 
to me...
(2) Why did they not use "final"?

The point is that not being able to add your own customised fields, is, I 
think, limiting significantly what one can do.
In my case, I have derived a SyslogLayout from PatternLayout, so as to be able 
to prepend and append
some specific information to the syslog messages, information which is expected 
by our existing monitoring systems.

But at that stage I can only use the data populated in LoggingEvent (or any 
other data which is more or less global in its nature).
What I cannot do (but need to) is to get event-contextual data, e.g. event-id, 
if we want to add such data per every logged message.

Unless I am missing the better/intended way of doing what I want, I truly think 
this is a harsh limitation,
but be happy to hear differing opinions.

Thanks again,
Barak
________________________
Barak Simon
GED IT Core Platform
190 George St. Sydney, 2000
Phone +61 2 925 85070
Fax      +61 2 925 95050


                                                                                
                                                                        
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log4cxx-user@xxxxxxxxxxxxxxxxxx                                                 
               
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                      09/12/2004 16:03         Subject:  Re: No Virtual 
Destructor for LoggingEvent                                                     
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On Dec 8, 2004, at 10:12 PM, Barak Simon wrote:

> Hi,
> I need to extend LoggingEvent to set some extra information in it,
> but it seems that despite being stated in its doco:
> "This class is of concern to those wishing to extend log4cxx",
>
> the destructor is not virtual!
>
> I know that extending it and instantiating it in a customised Logger
> class will break at present the SocketAppender,
> but am willing to take that risk, hoping the SocketAppender future
> implementation will have a less strict format.
>
> Is there any chance the next release will virtualise the LoggingEvent
> destructor?
>
> Many thanks,
> Barak
> _____

I don't believe that LoggingEvent has any virtual functions (other than
those inherited from ObjectImpl) and is not designed for extension.
Item 15 in Effective Java is "Design and document for inheritance or
prohibit it".  LoggingEvent is not designed or documented for
inheritance (and intentionally so).  There isn't the C++ equivalent of
declaring LoggingEvent as "final", but if there were I would.

You can "extend"  LoggingEvent by adding strings to the mapped
diagnostic context, but I assume that isn't satisifactory.  If you'd
want to discuss your use cases, maybe we could find some maintainable
approach.








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