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https://issues.apache.org/jira/browse/LOG4J2-3113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17373162#comment-17373162
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Ralph Goers commented on LOG4J2-3113:
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Now you have me totally confused. You are making a call using System.Logger's
interface. That interface doesn't accept Suppliers for the parameters, only for
the message itself. So there is no way you can possibly pass in two Suppliers
and have them end up calling something in the Log4j API that accepts Suppliers
as parameters unless Log4jSystemLogger is modified to check the parameters at
runtime using instanceof. But I don't think I would want to do that as you are
now making System.Loggers API do something it wasn't designed to handle.
For some reason this whole time I was thinking you were saying there was a
problem in the Log4j API. I can see in your original description that you did
mention System.Logger but then you mentioned LOG4J2-599 which had nothing to do
with System.Logger as it hadn't been implemented yet, much less the log4j-jpl
module.
> Support Supplier<> in varargs log message parameters
> ----------------------------------------------------
>
> Key: LOG4J2-3113
> URL: https://issues.apache.org/jira/browse/LOG4J2-3113
> Project: Log4j 2
> Issue Type: Improvement
> Components: API
> Affects Versions: 2.14.1
> Reporter: Markus Spann
> Priority: Minor
>
> It would be very useful, to give special treatment to message parameters of
> type {{java.util.function.Supplier<T>}} by calling {{get()}} rather than
> {{toString()}} on it while creating the log message.
> Message parameters (i.e. method calls that return the parameter) that are
> expensive to compute can thus be computed lazily.
> What's more, the logging call reads more naturally just like all other
> logging calls that use wildcards and parameters.
> {code:java}
> java.lang.System.Logger logger = System.getLogger("toto");
> // already supported style using a single Supplier
> logger.log(Level.DEBUG, () -> "Contents of array: " +
> Arrays.deepToString(array));{code}
> {code:java}
> // compiles but calls toString() rather than Supplier.get()
> logger.log(Level.DEBUG, "Contents of array: {}", (Supplier<String>) () ->
> Arrays.deepToString(array));{code}
> I've looked through the log4j2 Jira and found issue LOG4J2-599 in which a
> similar request was previously discussed without actually adding the feature
> to log4j2.
> (Note: Strangely Java requires the cast to (Supplier<String>).)
> My suggestion is to add Supplier support by enhancing method
> {{org.apache.logging.log4j.util.StringBuilders.appendSpecificTypes()}}.
> I will provide a Pull Request if you agree to the enhancement.
>
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