Some (ok, a lot of) feedback:
- `private static ConcurrentMap<String, Level> levels` should be final.
- `private static Object constructorLock` should be final. In fact, code
inspection flags this as a warning since code synchronizes on it.
- The standard Level constants should be instantiated in a static initializer
like in my original code. Otherwise the order they are instantiated in is
unpredictable, and DEBUG (for example) may even have a different ordinal each
time the JVM starts.
- Level isn't abstract. However, you use `new Level("xxx", n) {}` (brackets)
for Level.OFF, ExtendedLevels.NOTE, and ExtendedLevels.DETAIL, but you use `new
Level("xxx", n)` (no brackets) for other levels. IMO, Level should be abstract
(so that there's always exactly one instance of every class that extends Level,
just like a real enum), and the levels should all use {} to construct. However,
if we don't make Level abstract, then we should remove {} from OFF, NOTE, and
DETAIL because it's unnecessary.
- The way StdLevel appears in the middle of Level separates its static fields
from its instance fields, constructor, and methods. It makes it difficult to
read. I have to scroll pass StdLevel to see the rest of Level. Can we please
move StdLevel to the bottom of Level?
- This is more personal preference, but I don't like abbreviating things in
class names. What is Std? We may know, but does everyone? To someone unfamiliar
with English, Standard is easy to translate, but they have to first figure out
that Std is short for Std. Can be please un-abbreviate this to StandardLevel?
- I disagree with this approach:
if (levels.containsKey(name)) {
Level level = levels.get(name);
if (level.intLevel() != intLevel) {
throw new IllegalArgumentException("Level " + name + " has
already been defined.");
}
ordinal = level.ordinal;
}
This allows multiple Levels with the same name/intLevel to be instantiated,
which prevents equality testing (level == Level.OFF) from being 100%
deterministic. It should really be this:
if (levels.containsKey(name)) {
throw new IllegalArgumentException("Level " + name + " has
already been defined.");
}
- I think we should make all of the methods of Level final. Custom levels
shouldn't be able to change their behavior, IMO. Alternatively, if we don't
make Level abstract, we should make it final.
- Level has no JavaDoc. The Level constants in Level have no JavaDoc. That
needs to be fixed.
- I'm still not convinced StdLevel/StandardLevel is necessary. It seems like an
anti-pattern to me. From what I can tell (please let me know if I'm missing
something), StdLevel's entire purpose is to allow us to still switch on the
standard levels. I think that's a bad reason to create an enum whose constants
mirror Level. The primary problem with the StdLevel is that the conversion from
a Level to a StdLevel in many cases happens __on every logging event__. That's
going to be hugely inefficient. Really, when a custom Level is created, it
should be created with an equivalent standard Level (or StdLevel). There are
several ways to accomplish this that are open to discussion, but I don't think
the current StdLevel.getStdLevel is the right approach. One alternative:
private final Level standardLevel;
protected Level(String name, int level, Level mapToOtherFrameworksAs) {
this(name, level);
this.standardLevel = mapToOtherFrameworksAs;
}
private Level(String name, int level) {
// same as now
this.standardLevel = this;
}
public final Level getStandardLevel() {
return this.standardLevel;
}
This does, admittedly, have some problems. Another alternative that I could
also be happy with that keeps the StandardLevel enum:
private final StandardLevel standardLevel;
protected Level(String name, int level, StandardLevel
mapToOtherFrameworksAs) {
this(name, level);
this.standardLevel = mapToOtherFrameworksAs;
}
private Level(String name, int level) {
// same as now
this.standardLevel = this;
}
public final StandardLevel getStandardLevel() {
return this.standardLevel;
}
Nick
On Jan 26, 2014, at 1:38 PM, Ralph Goers wrote:
> I’ve committed the changes. Take a look at ExtendedLevels.java,
> ExtendedLevelTest.java and log4j-customLevel.xml in the log4j-core test
> directories to see how it works.
>
> Ralph
>
> On Jan 26, 2014, at 1:19 AM, Remko Popma <remko.po...@gmail.com> wrote:
>
>> I'm very curious! Can't wait to see it. Go for it!
>>
>> On Sunday, January 26, 2014, Ralph Goers <ralph.go...@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.go...@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.po...@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 <garydgreg...@gmail.com> wrote:
>>>> On Fri, Jan 24, 2014 at 11:48 AM, Remko Popma <remko.po...@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 <garydgreg...@gmail.com>
>>>> wrote:
>>>> On Thu, Jan 23, 2014 at 10:45 PM, Remko Popma <remko.po...@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 <garydgreg...@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: garydgreg...@gmail.com | ggreg...@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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