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https://jira.qos.ch/browse/SLF4J-371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18675#comment-18675
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Herman Bovens commented on SLF4J-371:
-------------------------------------

Any updates?  Log4j2 has this exact feature already since version 2.4 (almost a 
year ago).

> Support the lambda expression in the Logger
> -------------------------------------------
>
>                 Key: SLF4J-371
>                 URL: https://jira.qos.ch/browse/SLF4J-371
>             Project: SLF4J
>          Issue Type: Improvement
>          Components: Core API
>    Affects Versions: 1.7.22
>            Reporter: MiNG
>            Assignee: SLF4J developers list
>
> In some cases, we don't want to calculate the expression for logging eagerly 
> cause the performance reason. Then, we would write the code like the 
> following:
> ```
>     if (LOGGER.isWarnEnabled())
>     {
>        LOGGER.warn("some message: {}", Json.serialize(obj));
>     }
> ```
> Before JDK8, there is no way to encapsulate the above code, because the 
> expression is always calculated before passed as an argument. So, many "if"s 
> appear in the code and smell badly.
> Now, the lambda expression is supported by JDK8, the above could be 
> simplified like following:
> ```
>     LOGGER.warn(formatter -> formatter.format("some message: {}", 
> Json.serialize(obj)));
> ```
> With the default method definition in the org.slf4j.Logger:
> ```
>     public interface Logger
>     {
>       default void warn(Function<MessageFormatter, String> messageSupplier)
>       {
>         if (this.isWarnEnabled())
>         {
>           /* Calculate the expression only if the WARN level logging is 
> enabled. */
>           this.warn(messageSupplier.apply(this.getFormatter()));
>         }
>       }
>     }
> ```



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