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https://jira.qos.ch/browse/SLF4J-371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=19164#comment-19164
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Jānis commented on SLF4J-371:
-----------------------------
Also it would be nice if we could use something like this:
{code:java}
log.debug(() -> "key:"+key+" value:"+value );{code}
And hopefully java at some point add proper string interpolation support, and
than we could use something like:
{code:java}
log.debug(() -> "key:$key value:$value" );{code}
Pros:
1. Only one lambda is used.
> 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:
> {code:java}
> if (LOGGER.isWarnEnabled())
> {
> LOGGER.warn("some message: {}", Json.serialize(obj));
> }{code}
> 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:
> {code:java}
> LOGGER.warn(formatter -> formatter.format("some message: {}",
> Json.serialize(obj)));{code}
> With the default method definition in the org.slf4j.Logger:
> {code:java}
> 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()));
> }
> }
> }{code}
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