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https://issues.apache.org/jira/browse/LOG4J2-599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13963807#comment-13963807
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Nick Williams commented on LOG4J2-599:
--------------------------------------
I've been thinking about this a lot. We wouldn't even have to change the API,
per se, just the documentation for the API. Essentially, for all ***(String,
Object...) methods, we say, "Any parameters that are strings are used as-is.
Any parameters that implement {{java.util.function.Supplier}} or
{{java.util.concurrent.Concurrent}} will be invoked and the return value will
replace the parameter. Otherwise, {{toString}} will be called on the parameter."
Then, our Java 8 users can simply do this:
{code:java}logger.info("Message with a complex parameter {}.", (Supplier)() ->
{ /* code that returns parameter value */ });{code}
> Support lambda functions (or similar) for log message parameters
> ----------------------------------------------------------------
>
> Key: LOG4J2-599
> URL: https://issues.apache.org/jira/browse/LOG4J2-599
> Project: Log4j 2
> Issue Type: Brainstorming
> Components: Core
> Reporter: Matt Sicker
> Priority: Minor
>
> It would be nice if we could support 0-param lambda functions (or the
> equivalent: interfaces with a single empty-parameter message call), or more
> simply, allow Runnables (or something similar) to be passed which will be
> dynamically executed if the log message is enabled.
> The use case here is that although string construction of the log message is
> a performance issue that is already solved quite well, the problem of adding
> in information to the log message that makes other calculations still needs
> to be wrapped in an if check.
> I'm not sure if it'd be best to just use Runnable, or create a new interface,
> or try to emulate how Java 1.8 lambdas work via an interface with a single
> method defined. The details here would still need to be fleshed out, but I
> think this sort of feature could be rather handy (especially in a Java 1.8+
> environment, or in Groovy/Scala/etc.).
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