“在警告级别使用 slf4j 进行日志记录”是否会阻止运行“logger.debug(...”

Question

i've a question about processing log lines according to level like;

logger.debug("hello i am a log line not so neccessary, also log level is setted WARN and some complexProcessResult-> {}",
doSomeWorkwhichTakeslongTime());

If logger level sets to WARN so does it call the process "doSomeWorkwhichTakeslongTime()" because jsonizing some classes, take so much time, and i dont want to run this in production. To achieving this, is it enough setting the log level as "warn"?

Answer 1

No, if you use this specific method call, then changing the log level would have no impact on whether or not doSomeWorkWhichTakesLongTime() is being called or not.

It can't have an effect, because the Java language specifies that the parameter values need to be computed before the method is called.

There are two possible workarounds:

The "ugly" one is to use isDebugEnabled() :

if (logger.isDebugEnabled()) {
    logger.debug("hello i am a log line not so neccessary, also log level is setted WARN and some complexProcessResult-> {}", doSomeWorkwhichTakeslongTime());
}

The other one is a bit trickier, but potentially nicer: Have the heavy lifting happen in the toString() of an object that is either cheap to construct or that you have accessible anyway:

logger.debug("hello i am a log line not so neccessary, also log level is setted WARN and some complexProcessResult-> {}", someObjectThatDescribesTheOutput)

and have someObjectThatDescribesTheOutput have a toString method a little like this:

public String toString() {
  return doSomeWorkwhichTakeslongTime();
}