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From "Nick Williams (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-599) Support lambda functions (or similar) for log message parameters
Date Wed, 09 Apr 2014 16:25:24 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13964339#comment-13964339

Nick Williams commented on LOG4J2-599:

To be clear, {{toString}} of a {{Supplier}} is completely meaningless. It'll look something
like "com.MyClass$lambda$18972349\ou98!uc". If someone provides a {{Supplier}}, they don't
mean for you to call {{toString}} on it. {{Callable}}, on the other hand, I can see your point.
Maybe we only support a "smart API" for {{Supplier}}?

The problem with a separate API is it actually makes it MORE difficult to use. What if MOST
of my arguments are simple, but ONE of them needs to be evaluated on a deferred basis? Consider

{code:java}logger.trace("Enter {} {} {} {}", argument1, argument2, (Supplier)() -> argument3.someMethod(),

Having a separate Supplier API would make this impossible. They'd have to use a lambda for
all four arguments.

> 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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