As Ralph states, this is already supported by JSON Template Layout
<https://logging.apache.org/log4j/2.x/manual/json-template-layout.html> (JTL).
(Note that `JsonLayout` is deprecated in favor of `JsonTemplateLayout`.)
But Ralph's statement needs a correction: You don't need to fallback to
Pattern Layout, JTL supports `MapMessage` out of the box
<https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-map>
:
"message": {
"$resolver": "map"
}
Note that JTL also supports field injection using `ThreadContext`, aka.
MDC. You can set your custom fields using `ThreadContext.put(String,String)`
et al. <https://logging.apache.org/log4j/2.x/manual/thread-context.html>
and include them in your JTL event template:
"message": {
"$resolver": "mdc"
}
JTL's map resolver (used by both `map` and `mdc` resolvers) is pretty
powerful. See its docs for further configuration options
<https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#map-resolver-template>
.
Please let us know if you have any further questions.
On Sun, Apr 7, 2024 at 8:46 PM Ralph Goers <ralph.go...@dslextreme.com>
wrote:
> I wasn’t aware GoLang had a “standard” logger. Last time I checked
> GoLang’s logging library was awful.
>
> Log4j 2 has supported what you want ever since Json Template Layout was
> added. See
> https://logging.apache.org/log4j/2.x/manual/json-template-layout.html.
>
> To get what you want just specify a pattern (See PatterLayout) to the
> JsonTemplateLayout configuration.
>
> In addition, you can also include the Map fields as individual attributes.
>
> Here is an example configuration for the message
>
> "message": {
> "$resolver": "pattern",
> "pattern": “%K"
> },
>
>
> Ralph
>
> > On Apr 7, 2024, at 9:28 AM, Clayton Wohl <claytonw...@gmail.com> wrote:
> >
> > The Golang standard library lets you do this:
> >
> > slog.Info("showing named arguments with structured logging",
> > slog.Bool("some-bool", true),
> > slog.Int("some-int", 123),
> > slog.Float64("some-float64", 1.234),
> > slog.String("some-string", "xyz"))
> >
> > which outputs the following at runtime:
> >
> > {"time":"2024-04-07T11:10:04.925291-05:00","level":"INFO","msg":"showing
> > named arguments with structured
> >
> logging","some-bool":true,"some-int":123,"some-float64":1.234,"some-string":"xyz"}
> >
> > I'd like to do this in Java. This seems to be a fairly common use
> > case. Log4j's API doesn't seem to offer this. The closest I can get
> > is:
> >
> > Logger logger = LogManager.getLogger();
> >
> > logger.info(new MapMessage()
> > .with("someInt", 123)
> > .with("someFloat", 1.23456)
> > .with("someBool", true)
> > .with("someString", "abc"));
> >
> > which outputs the following at runtime. Notice that it just converted
> > the MapMessage to a string and put that in the JSON message field.:
> >
> >
> {"@timestamp":"2024-04-07T16:26:21.232Z","ecs.version":"1.2.0","log.level":"INFO","message":"someBool=\"true\"
> > someFloat=\"1.23456\" someInt=\"123\"
> > someString=\"abc\"","process.thread.name
> ":"main","log.logger":"demo.Main"}
> >
> > Is it possible that log4j3 offer something like what Golang's slog does?
> >
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