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https://issues.apache.org/jira/browse/LOG4J2-599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14660945#comment-14660945
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Remko Popma commented on LOG4J2-599:
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That is the use case for this ticket: users on Java 8 will be able to avoid the
explicit level check and instead write
{code}
logger.trace("Some expensive operation returned {}", () ->
expensiveOperation());
{code}
resulting in more compact and cleaner code.
The only logging product that I am aware of that currently supports lambda
expressions for lazy logging is the JDK
[Logger|http://docs.oracle.com/javase/8/docs/api/java/util/logging/Logger.html#log-java.util.logging.Level-java.util.function.Supplier-].
But IMHO the JDK Logger is only doing a partial job: it only lazily constructs
the whole log message. There is no API for lazily constructing message
parameters.
I think keeping up to date with Java language developments makes this a
"strategic" feature that adds to the reasons why Log4j 2 is the logging library
of choice for our users.
> 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
> Labels: Java8
>
> 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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