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Date: Sat, 20 Aug 2016 10:27:20 +0000 (UTC)
From: =?utf-8?Q?Mikael_St=C3=A5ldal_=28JIRA=29?= <jira@apache.org>
To: log4j-dev@logging.apache.org
Message-ID: <JIRA.12998265.1471542826000.362000.1471688840477@Atlassian.JIRA>
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Subject: [jira] [Commented] (LOG4J2-1531) Change attribute and component
 values from String to Object
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archived-at: Sat, 20 Aug 2016 10:27:22 -0000


    [ https://issues.apache.org/jira/browse/LOG4J2-1531?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D154=
29322#comment-15429322 ]=20

Mikael St=C3=A5ldal commented on LOG4J2-1531:
----------------------------------------

I think that this is a misuse of the {{@Plugin}} mechanism, it is designed =
for configuration files rather than programmatic configuration.

If we want rich programmatic configuration, I think we should bypass the re=
flection based {{@Plugin}} mechanism altogether.

What about overloading the add methods in {{ConfigurationBuilder}} to also =
take a programmaticly constructed Filter, Layout, Appender instances? You c=
an then create ad-hoc Filters, Layouts, Appenders only for this purpose, an=
d they should not need to have any annotations.

We can also create some Single Abstract Method abstract Filters, Layouts, A=
ppenders for this purpuse to make it possible to use Java 8 lambdas conveni=
ently.


> Change attribute and component values from String to Object
> -----------------------------------------------------------
>
>                 Key: LOG4J2-1531
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1531
>             Project: Log4j 2
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 2.6.2
>            Reporter: Roger Kapsi
>         Attachments: log4j2-1531-1.0.patch
>
>
> I was looking into creating a ConfigurationFactory/Builder that is backed=
 by a Clojure DSL. It works rather beautifully until I tried to create a fi=
lter that is backed by a Clojure function. There is literally  no way to pa=
ss arbitrary objects into a PluginFactory. All component values and attribu=
tes are assumed to be Strings.
> {code:java}
> (configuration
>   (appender "stdout" "CONSOLE"
>     (layout "PatternLayout"
>       (attribute "pattern" "%d [%t] %-5level: %msg%n"))
>     (filter "ClojureFilter"
>       ;; This LoC doesn't work: addAttribute(key, value)
>       ;; will store the toString() of the value. Bummer.
>       ;; I'd the so easy and beautiful if it didn't.
>       (attribute "fn" (fn [logger & more] (println logger)))))
>  =20
>   (logger "TestLogger" Level/INFO
>     (appender-ref "rolling")
>     (attribute "additivity" false))
>   (root-logger Level/DEBUG=20
>     (appender-ref "rolling")))
> {code}
> {code:java}
> @Plugin(name =3D "ClojureFilter", category =3D Node.CATEGORY, elementType=
 =3D Filter.ELEMENT_TYPE, printObject =3D true)
> class ClojureFilter extends AbstractFilter {
>   @PluginFactory
>   public static ClojureFilter createFilter(
>       @PluginAttribute("fn") IFn fn, ...) {
>      return new ClojureFilter(fn, ...);
>   }
> }
> {code}


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