How about starting with something very simple at first?
We provide a tool that generates the source code for a custom logger
interface.
To invoke the tool the user passes it the fully qualified name of the
interface, and a list of NAME=INTLEVEL custom log levels.
The generated source code contains both the interface and an
implementation. The implementation is an inner class of the interface (so
users only need to manage one single file).
The generated interface is annotated with the class name of the
implementation class.
At runtime, users call LogManager.getCustomLogger(Class, String) to get a
custom logger instance.
The LogManager then uses the annotation on the interface class to
instantiate objects of the implementation class.
Example tool invocation:
java org.apache.logging.log4j.util.Generate com.mycomp.myproject.MyLogger
DIAG=350 NOTICE=450 VERBOSE=550
Generated code:
@CustomLoggerImplementation(MyLogger.Impl.class)
public interface MyLogger extends Logger {
void diag(Marker marker, Message msg);
void diag(Marker marker, Message msg, Throwable t);
// ... other methods
public static final class Impl extends AbstractLoggerWrapper implements
MyLogger {
private final static Level DIAG = Level.getOrCreateLevel("DIAG", 350);
private final static Level NOTICE = Level.getOrCreateLevel("NOTICE",
450);
private final static Level VERBOSE = Level.getOrCreateLevel("VERBOSE",
550);
public Impl(final AbstractLogger logger) {
super(logger, logger.getName(), logger.getMessageFactory());
}
public void diag(Marker marker, Message msg) {
logger.log(DIAG, marker, msg);
}
public void diag(Marker marker, Message msg, Throwable t) {
logger.log(DIAG, marker, msg, t);
}
// ... other methods
}
}
LogManager:
public static <T extends Logger> T getCustomLogger(Class<T> cls, String
name) {
Logger wrapped = getLogger(name);
return wrap(cls, wrapped);
}
private static <T extends Logger> T wrap(Class<T> cls, Logger wrapped) {
CustomLoggerImplementation annotation =
cls.getAnnotation(CustomLoggerImplementation.class);
Class<?> implClass = annotation.value();
try {
Constructor<?> constr = implClass.getConstructor(Logger.class);
return (T) constr.newInstance(wrapped);
} catch (Exception ex) {
throw new IllegalStateException(
"Unable to construct instance of custom logger class "
+ implClass.getName(), ex);
}
}
On Monday, January 27, 2014, Scott Deboy <scott.de...@gmail.com> wrote:
> I know we can't do what I would like via configuration. My point was to
> primarily to spark discussion on how we could make the api as simple as
> possible.
>
> I'm ok with where we are on the custom level support.
>
> I do think this brings us back around to adding built in levels, in a
> separate thread.
>
> I'm really pleased with how things are coming together. Good stuff.
>
> Scott
> On Jan 26, 2014 9:25 PM, "Nicholas Williams" <
> nicho...@nicholaswilliams.net> wrote:
>
> Yes, I was saying that. But, unless I'm misunderstanding, Scott doesn't
> want the user to even have to write the interface. He wants them to just
> configure it and the interface become available "magically." I was pointing
> out that there's a disconnect between when the configuration is used
> (runtime) and when the user needs the interface (compile time).
>
> Unless we provide a code-generation tool for the user to run from the
> command line or from Ant/Maven/Gradle, they're going to have to write the
> interface themselves.
>
> Nick
>
> Sent from my iPhone, so please forgive brief replies and frequent typos
>
> On Jan 26, 2014, at 22:49, Remko Popma <remko.po...@gmail.com> wrote:
>
> Nick, I thought that you meant that users would provide their own
> interface, like this:
> public interface MyLogger extends Logger {
> @LoggingLevel(name="DIAG")
> void diag(String message);
> // optional other methods
> }
>
> That way, this interface exists at compile time.
>
> On Monday, January 27, 2014, Nicholas Williams <
> nicho...@nicholaswilliams.net> wrote:
>
> Scott, invokedynamic and javassist...those are all /runtime/ things. The
> user needs Logger#notice to be available at compile time. Those are not
> compatible.
>
> Nick
>
> Sent from my iPhone, so please forgive brief replies and frequent typos
>
> > On Jan 26, 2014, at 22:37, Scott Deboy <scott.de...@gmail.com> wrote:
> >
> > Yes, I would like to declare in the config:
> >
> > Level: NOTICE, value: 232
> >
> > And in Java code be able to use logger.notice("some message").
> >
> > But I think that'd require invokedynamic..which would probably
> > require..javassist/ASM?
> >
> > I'd be ok with anything that's really close to that :)
> >
> > Scott
> >
> >
> >> On 1/26/14, Ralph Goers <ralph.go...@dslextreme.com> wrote:
> >> Scott would like users to add a level definition to the logging
> >> configuration and have everything else happen auto-magically. That
> would
> >> happen at run-time which is a bit late since the methods need to be
> >> available at compile time.
> >>
> >> I believe Scott said he would be fine if users had to do
> >>
> >> logger.log(SomeClass.SomeLevel, "message);
> >>
> >> but even that requires "SomeClass" to be available at compile time.
> >>
> >> So what Scott says he would like and what Nick is proposing are two
> >> different things.
> >>
> >> Ralph
> >>
> >>
> >>
> >>> On Jan 26, 2014, at 8:09 PM, Remko Popma <remko.po...@gmail.com>
> wrote:
> >>>
> >>> I actually thought that Nick's idea was the answer to that: users
> create a
> >>> custom interface, something like this:
> >>>
> >>> public interface MyLogger extends Logger {
> >>> @LoggingLevel(name="DIAG")
> >>> void diag(String message);
> >>> // optional other methods
> >>> }
> >>>
> >>> They get an instance of this interface by calling:
> >>> LogManager.getCustomLogger(MyLogger.class);
> >>>
> >>> LogManager has access to the processed configuration. The config has
> >>> <Levels><Level name="DIAG" intValue="450"> elements. During
> configuration
> >>> processing, the custom Level instances are created and registered, so
> on
> >>> the firs
>
>
