On 27.10.2010 15:08, Robert Elliot wrote:
> Ceki's said in the past that the answer is no. After all, what would
> it do? You have to bear in mind that it's intended to redirect log4j
> to slf4j - so it has to be slf4j implementation agnostic. So it can't
> actually *do* anything with programmatic attempts to change the levels
> of Logger instances or add Appenders, the most you could have is a no
> operation implementation. That would probably result in loads of null
> pointer exceptions as your dependent jars try to use objects retrieved
> via the API, not to mention that if your dependent jars actually need
> to do these things then they will be broken even if no exception is
> thrown immediately.
Indeed I have said as much in the past. However, if users are willing
to go through the trial and error process, I think we could add more
missing classes and/or methods with NOP implementations. As long as
the caller is satisfied with nop, things should be OK.
> (One possibility I could see is adding all the classes and methods to
> be binary compatible but making all the methods throw an
> UnsupportedOperationException explaining why log4j-over-slf4j only
> implements a small subset of log4j's API so that people aren't left
> wondering about ClassNotFoundExceptions - which might have saved you
> having this conversation, but wouldn't actually solve your problem.)
NOP could be a viable alternative.
> If you have a hard dependency on log4j that you can't change then I
> guess you have to use log4j.
I agree but may be the caller could be satisfied with NOP.
It should be possible to satisfy most callers except perhaps in
certain cases which could become rather hard to diagnose due to the
NOP trickery...
----- Original Message -----
From: "Jeremy Truelove"<[email protected]>
To: [email protected]
Sent: Wednesday, 27 October, 2010 1:58:27 PM
Subject: Re: [logback-user] Legacy Log4j Question
Unfortunately I don't have the ability to change these dependencies
and I don't know why they are coded in the way they are so they have
such a hard dependency on log4j. Is there any plan to add the rest of
the classes to log4j-over-slf4j just to support legacy jar dependency
issues?
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Robert Elliot
Sent: Wednesday, October 27, 2010 8:46 AM
To: logback users list
Subject: Re: [logback-user] Legacy Log4j Question
The question has to be why do your dependent jars need to call these
APIs in log4j? Unfortunately log4j does not differentiate between the
interface for firing off log events (the sort of thing SLF4J/Commons
logging provide) and its API for managing what is actually done for
them. As a general rule libraries should only be using the bare
minimum of logging (the equivalent of the SLF4J interface - which is
what log4j-over-slf4j implements) and only the end user application
should be defining things like appenders and turning logging on or
off.
If your dependent jars are using the log4j API for controlling what is
done with logging events then either they have a real dependency on
log4j for some good reason or else they are behaving badly. Without
knowing what these dependencies are, what they are doing and why
there's not much else can be said.
(Of course you always have the option of using log4j as your slf4j
implementation via slf4j-log4j; you can still pipe JULI& Commons
Logging to SLF4J and use SLF4J in your own code and so end up with a
single logging config file, just a log4j one rather than a logback
one.)
----- Original Message -----
From: "Jeremy Truelove"<[email protected]>
To: [email protected]
Sent: Wednesday, 27 October, 2010 1:30:22 PM
Subject: [logback-user] Legacy Log4j Question
So I've been porting some of our services to use Logback over log4j
and I've been using the log4j-over-slf4j jar to spoof log4j for our
legacy dependencies. The only issue is log4j-over-slf4j doesn't
implement many of the classes of log4j so I'm seeing a decent few
class not found exceptions from dependent jars. How have people got
around this? Is it enough to just put the nlog4j in your classpath
instead of the log4j-over-slf4j jar? I’d still like to use one
logback
config file to drive all my logging to a single log file. Thanks.
jt
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