LoggingHandler patch [was: Using Avalon/Logkit]

[Michael Gratton <mj...@recalldesign.com>]

Guys,

To further to my suggestions about using an interface for logging in 
core FOP components, I've produced a working implementation of my 
suggestion. After a precursory test using the command line, the changes 
seem to work fine.

The patch, for the "fop-0_20_3" branch in CVS, and the two additional 
required source files are available at:

   <http://web.vee.net/fop/LoggingHandlerImpl-2002031300.jar>

The two added files are src/org/apache/fop/apps/LoggingHandler.java and 
src/org/apache/fop/apps/LogkitLoggingHandler.java. The former is the 
LoggingHandler interface, which has replaced any use of 
org.apache.log.Logger in core FOP code. The latter is an implementation 
of LoggingHandler which uses Logkit and is Loggable (for Avalon).

I've identified three applications which use assume the use of Logkit 
for logging: The command line app, the FOP task for Ant and 
TestConverter. All three have been modified to use LogkitLoggingHandler 
and hence function in the exact same fashion as before. In addition, if 
no LoggingHandler is explicitly set on Driver, it by default uses an 
instance of LogkitLoggingHandler, again to make it behave the same as 
before.

Embedders who do not wish to use Logkit for logging can write their own 
implementation of LoggingHandler and call Driver.setLogger() prior 
invoking Driver.render().

There are three issues which need to be addressed before I would 
consider this code ready to commit:
  - Is the Loggable implementation of LogkitLoggingHandler sufficient 
for Avalon? Not really knowing how Avalon works, I'm not sure if 
implementing Loggable on LogkitLoggingHandler is sufficient, or will an 
"AvalonDriver" subclass of Driver be needed which translates between 
logging objects be required? Can any Avalon gurus comment on this?
  - MessageHandler's use of Logger for screen output needs to be fixed. 
This will probably require a setLoggingHandler() method to be added, and 
ensuring it gets called prior to MessageHandler getting invoked.
  - ToBeImplementedProperty grabs a Logger out of thin air, this should 
probably use MessageHandler or just throw an exception (as outlined in 
the comments for that class in the patch).

Outstanding, non-essential work includes:
  - Perhaps renaming {get|set}Logger() on Renderer and similar classes 
to {get|set}LoggingHandler()
  - Adding optional implementations of LoggingHandler for Log4J, 1.4's 
logging mechanism, and any others.

Please have a look at the patch, try it out applied to the "fop-0_20_3" 
branch and let me know if you have any suggestions. I'll fix up the 
three issues above sometime in the next few days and post a new patch.

Provided it all works well, would anyone mind having these changes 
committed to the tree?

Thanks,
Mike.

-- 
Michael Gratton <mj...@recalldesign.com>
Recall Design <http://www.recalldesign.com/>
s: 53 Gilbert Street Adelaide SA 5000 Australia
t: +61 8 8217 0500 f: +61 8 8217 0555

Re: LoggingHandler patch [was: Using Avalon/Logkit]

[Jeremias Maerki <je...@outline.ch>]

Michael

It's me again. I'm against that for the reasons layed out in my mail
from a few moments ago. I appreciate your effort but I think this is the
wrong way. I'm not a committer so my opinion doesn't count but I have
grown very fond of FOP to just be silent.

Cheers,
Jeremias Märki

mailto:jeremias.maerki@outline.ch

OUTLINE AG
Postfach 3954 - Rhynauerstr. 15 - CH-6002 Luzern
Tel. +41 41 317 2020 - Fax +41 41 317 2029
Internet http://www.outline.ch


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