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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: Enums and Custom Levels - completed.
Date Mon, 27 Jan 2014 18:17:59 GMT
Yes that's the idea. 

Gary

-------- Original message --------
From: Ralph Goers <ralph.goers@dslextreme.com> 
Date:01/27/2014  11:19  (GMT-05:00) 
To: Log4J Developers List <log4j-dev@logging.apache.org> 
Subject: Re: Enums and Custom Levels - completed. 

If the user creates a custom Logger Wrapper then they can just code against that and not use
an interface, correct?

Ralph

On Jan 27, 2014, at 6:40 AM, Nick Williams <nicholas@nicholaswilliams.net> wrote:

Wrapping a logger /implementation/ is fine. But the user needs an /interface/ to program against.
That interface should extend Logger rather than re-define all of Logger's methods.

Nick

On Jan 27, 2014, at 8:24 AM, Gary Gregory wrote:

Please note that in the case of domain specific logging (DSL!), I do not want to extend, I
want to wrap a logger. See my DEFCON example.

Gary


On Sun, Jan 26, 2014 at 6:51 PM, Nick Williams <nicholas@nicholaswilliams.net> wrote:
Generating a logger /interface/ is going to be hard. Sure, writing the code automatically
will be a piece of cake. But then what do we do with that code? The user needs to program
against it. So we have to have a command-line utility or Maven/Ant plug-in to generate the
source pre-compile. However, since the vast majority of users are using IDEs, those IDEs will
still warn them about the interface not existing until they have run the utility to generate
the source.

I think a better approach would be to allow the user to define an interface that /must/ extend
Logger. That interface may contain any methods that match the following signatures (the interface
must have at least one method and there is no limit to the number of methods it may have):

void(Marker, Message)
void(Marker, Message, Throwable t)
void(Marker, Object)
void(Marker, Object, Throwable t)
void(Marker, String)
void(Marker, String, Object...)
void(Marker, String throwable)
void(Message)
void(Message, Throwable t)
void(Object)
void(Object, Throwable t)
void(String)
void(String, Object...)
void(String throwable)

Each method /must/ be annotated with @LoggingLevel(name = "levelName"). Now LogManager has
a few new methods:

<T extends Logger> T getCustomLogger(Class<T> loggerClass)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, Class<?>)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, Class<?>, MessageFactory)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, MessageFactory)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, Object)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, Object, MessageFactory)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, String)
<T extends Logger> T getCustomLogger(Class<T> loggerClass, String, MessageFactory)

The user can then obtain such a logger like so, etc.:

MyLogger logger = LogManager.getCustomLogger(MyLogger.class);

Log4j will generate an implementation of MyLogger that extends the default implementation,
cache that implementation so that it doesn't have to be implemented again, and then instantiate/cache
the logger instance like normal.

Make sense?

N

On Jan 26, 2014, at 5:32 PM, Scott Deboy wrote:

Yes that's what I was thinking.

Scott

On Jan 26, 2014 3:18 PM, "Remko Popma" <remko.popma@gmail.com> wrote:
Scott,
The way I interpreted Gary's idea was that based on user-specified custom levels, we would
generate an extension of the Logger interface that has a method for each of the custom levels
(well, actually 14 methods for each level :-) ).
I haven't really thought about how users would specify their custom levels, as long as the
tool can know what methods to generate. 

We could go one step further and generate the Level subclass from configuration as well. I
suppose that would entail adding a new <Levels> element, with sub-elements like <Level
name="DETAIL" intLevel="450" />... Is that what you are thinking of?

I would be fine with that too, but would like to first focus on generating the extended Logger
interface.



On Mon, Jan 27, 2014 at 5:29 AM, Scott Deboy <scott.deboy@gmail.com> wrote:
Is there a way to generate code/update the Levels enumeration so a new
Level class isn't required?

Would be great to be able to use logger.detail("Detail message");

Is that what you're thinking of, Remko?

On 1/26/14, Ralph Goers <ralph.goers@dslextreme.com> wrote:
> I haven’t done anything to directly do that. However, custom levels need to
> be mapped to the standard levels in several places. It would be simple to
> add support for that wherever you want it.  Level.StdLevel.getStdLevel() is
> the method used to do that.
>
> Ralph
>
> On Jan 26, 2014, at 7:45 AM, Scott Deboy <scott.deboy@gmail.com> wrote:
>
>> Are these serialization-wise going to be the same as standard levels?
>>
>> Receivers and apps like Chainsaw would benefit from not requiring the
>> originating level class be included in the classpath.
>>
>> I'm thinking about socketreceiver and to a lesser extent
>> logfilepatternreceiver.
>>
>> Scott
>> On Jan 26, 2014 7:28 AM, "Scott Deboy" <scott.deboy@gmail.com> wrote:
>> So I assume we could build on this by adding the ability to generate these
>> custom levels from the config, with no user provided class required?
>>
>>
>>
>> On Jan 26, 2014 12:58 AM, "Ralph Goers" <ralph.goers@dslextreme.com>
>> wrote:
>> >
>> > I have completed the work on custom levels.  It uses a variation of
>> > Nick’s “extensible enum” class.  The major difference with what he
>> > proposed is that the custom enums must be declared in a class annotated
>> > with @Plugin(name=“xxxx” category=“Level”) for them to be usable during
>> > configuration.
>> >
>> > Are their any objections to me checking this in?  I’ll be doing the
>> > commit at around noon Pacific Daylight Time if I don’t hear any.
>> >
>> > Ralph
>> >
>> >
>> >
>> > On Jan 25, 2014, at 7:08 AM, Ralph Goers <Ralph.Goers@dslextreme.com>
>> > wrote:
>> >
>> >> I am working on the implementation of custom levels now.  I should have
>> >> it done today.
>> >>
>> >> Ralph
>> >>
>> >> On Jan 24, 2014, at 7:07 PM, Remko Popma <remko.popma@gmail.com>
>> >> wrote:
>> >>
>> >>> What is the best way to make progress on the custom levels
>> >>> implementation?
>> >>>
>> >>> Do we re-open LOG4J-41 or start a fresh Jira ticket? For
>> >>> implementation ideas, do we attach files to Jira, or create a branch?
>> >>>
>> >>> Remko
>> >>>
>> >>> On Saturday, January 25, 2014, Gary Gregory <garydgregory@gmail.com>
>> >>> wrote:
>> >>>>
>> >>>> On Fri, Jan 24, 2014 at 11:48 AM, Remko Popma <remko.popma@gmail.com>
>> >>>> wrote:
>> >>>>>
>> >>>>> Gary,
>> >>>>>
>> >>>>> The hard-coded levels were proposed because it seemed that the
>> >>>>> extensible enum idea raised by Nick was not going to be accepted.
>> >>>>> My original position was that Markers could fulfill the requirement
>> >>>>> but Nick and yourself made it clear that this was not satisfactory.
>> >>>>>
>> >>>>> With extensible enums and markers off the table it seemed that
the
>> >>>>> hard-coded levels was the only alternative, and discussion ensued
>> >>>>> about what these levels should be called and what strength they
>> >>>>> should have.
>> >>>>>
>> >>>>> During this discussion, several people, including me, repeatedly
>> >>>>> expressed strong reservations about adding pre-defined levels,
but
>> >>>>> by this time I think people were thinking there was no alternative.
>> >>>>>
>> >>>>> It looked like we were getting stuck, with half the group moving
in
>> >>>>> one direction ("add pre-defined levels!") and the other half
wanting
>> >>>>> to move in another direction ("don't add pre-defined levels!").
I
>> >>>>> asked that we re-reviewed our assumptions and try to reach a
>> >>>>> solution that would satisfy all users.
>> >>>>>
>> >>>>> We then decided to explore the option of using extensible enums
>> >>>>> again. This is still ongoing, but I haven't seen anyone arguing
>> >>>>> against this idea since we started this thread.
>> >>>>>
>> >>>>> Hard-coded levels and the extensible enum are different solutions
to
>> >>>>> the same problem.
>> >>>>
>> >>>>
>> >>>> Hello All:
>> >>>>
>> >>>> Absolutely not. See my DEFCON example.
>> >>>> Talking about an "extensible enum" is mixing design and
>> >>>> implementation, we are talking about 'custom' and/or 'extensible'
>> >>>> levels.
>> >>>> Custom/Extensible levels can be designed to serve one or all of:
>> >>>>
>> >>>> - Allow inserting custom levels between built-in levels.
>> >>>> - Allow for domain specific levels outside of the concept of built-in
>> >>>> levels, the DEFCON example.
>> >>>> - Should the custom levels themselves be extensible?
>> >>>>
>> >>>> Gary
>> >>>>
>> >>>>>
>> >>>>> The extensible enum solution satisfies all of us who are opposed
to
>> >>>>> adding pre-defined levels, while also satisfying the original
>> >>>>> requirement raised by Nick and yourself. Frankly I don't understand
>> >>>>> why you would still want the pre-defined levels.
>> >>>>>
>> >>>>> Remko
>> >>>>>
>> >>>>>
>> >>>>>
>> >>>>> On Sat, Jan 25, 2014 at 12:53 AM, Gary Gregory
>> >>>>> <garydgregory@gmail.com> wrote:
>> >>>>>>
>> >>>>>> On Thu, Jan 23, 2014 at 10:45 PM, Remko Popma
>> >>>>>> <remko.popma@gmail.com> wrote:
>> >>>>>>>
>> >>>>>>> Gary,
>> >>>>>>>
>> >>>>>>> I think that's a very cool idea!
>> >>>>>>> Much more flexible, powerful and elegant than pre-defined
levels
>> >>>>>>> could ever be.
>> >>>>>>
>> >>>>>>
>> >>>>>> As I wrote: "I am discussing custom levels here with the
>> >>>>>> understanding that this is a separate topic from what the
built-in
>> >>>>>> levels are."
>> >>>>>>
>> >>>>>> I'm not sure why you want to make the features mutually
exclusive.
>> >>>>>> (Some) others agree that these are different features.
>> >>>>>>
>> >>>>>> I see two topics:
>> >>>>>>
>> >>>>>> - What are the default levels for a 21st century logging
framework.
>> >>>>>> Do we simply blindly copy Log4j 1? Or do we look at frameworks
from
>> >>>>>> different languages and platforms for inspiration?
>> >>>>>> - How (not if, I think we all agree) should we allow for
custom
>> >>>>>> levels.
>> >>>>>>
>> >>>>>> Gary
>> >>>>>>
>> >>>>>>> It definitely makes sense to design the extensible enum
with this
>> >>>>>>> potential usage in mind.
>> >>>>>>>
>> >>>>>>> Remko
>> >>>>>>>
>> >>>>>>>
>> >>>>>>> On Friday, January 24, 2014, Gary Gregory <garydgregory@gmail.com>
>> >>>>>>> wrote:
>> >>>>>>>>
>> >>>>>>>> I am discussing custom levels here with the understanding
that
>> >>>>>>>> this is a separate topic from what the built-in
levels are. Here
>> >>>>>>>> is how I convinced myself that custom levels are
a “good thing”.
>> >>>>>>>>
>> >>>>>>>> No matter which built-in levels exits, I may want
custom levels.
>> >>>>>>>> For example, I want my app to use the following
levels DEFCON1,
>> >>>>>>>> DEFCON2, DEFCON3, DEFCON4, and DEFCON5. This might
be for one
>> >>>>>>>> part of my app or a whole subsystem, no matter,
I want to use the
>> >>>>>>>> built-in levels in addition to the DEFCON levels.
It is worth
>> >>>>>>>> mentioning that if I want that feature only as a
user, I can
>> >>>>>>>> “skin” levels in a layout and assign any label
to the built-in
>> >>>>>>>> levels. If I am also a developer, I want to use
DEFCON levels in
>> >>>>>>>> the source code.
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> At first, my code might look like:
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> logger.log(DefconLevels.DEFCON5, “All is quiet”);
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> Let’s put aside for now the type of DefconLevels.DEFCON*
objects.
>> >>>>>>>> I am a user, and I care about my call sites.
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> What I really want of course is to write:
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> defconLogger.defcon5(“All is quiet”)
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> Therefore, I argue that for any “serious” use
of a custom level,
>> >>>>>>>> I will wrap a Logger in a custom logger class providing
call-site
>> >>>>>>>> friendly methods like defcon5(String).
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> So now, as a developer, all I care about is DefConLogger.
It
>> >>>>>>>> might wrap (or subclass) the Log4J Logger, who knows.
The
>> >>>>>>>> implementation of DefConLogger is not important
to the developer
>> >>>>>>>> (all I care is that the class has ‘defconN’
method) but it is
>> >>>>>>>> important to the configuration author. This tells
me that as a
>> >>>>>>>> developer I do not care how DefConLogger is implemented,
with
>> >>>>>>>> custom levels, markers, or elves. However, as configuration
>> >>>>>>>> author, I also want to use DEFCON level just like
the built-in
>> >>>>>>>> levels.
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>> The configuration code co
>> >>>>
>> >>>>
>> >>>>
>> >>>>
>> >>>> --
>> >>>> E-Mail: garydgregory@gmail.com | ggregory@apache.org
>> >>>> Java Persistence with Hibernate, Second Edition
>> >>>> JUnit in Action, Second Edition
>> >>>> Spring Batch in Action
>> >>>> Blog: http://garygregory.wordpress.com
>> >>>> Home: http://garygregory.com/
>> >>>> Tweet! http://twitter.com/GaryGregory
>> >>
>> >>
>> >
>
>

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-- 
E-Mail: garydgregory@gmail.com | ggregory@apache.org 
Java Persistence with Hibernate, Second Edition
JUnit in Action, Second Edition
Spring Batch in Action
Blog: http://garygregory.wordpress.com 
Home: http://garygregory.com/
Tweet! http://twitter.com/GaryGregory


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