CODEWITHSUNDEEP
javaexceptionlogginglog4j
derrdji
derrdji

Reputation: 13321

Substituting parameters in log message and add a Throwable in Log4j 2

I am trying to log an exception, and would like to include another variable's value in the log message. Is there a Logger API that does this? 

logger.error("Logging in user {} with birthday {}", user.getName(), user.getBirthdayCalendar(), exception);

Upvotes: 57

Views: 45090

Answers (2)

DominicEU
DominicEU

Reputation: 3631

Have you tried looking at ParameterizedMessage?

From the docs

Parameters:

messagePattern - The message "format" string. This will be a String containing "{}" placeholders where parameters should be substituted.

objectArgs - The arguments for substitution.

throwable - A Throwable

e.g.

logger.error(new ParameterizedMessage("Logging in user {} with birthday {}", user.getName(), user.getBirthdayCalendar()), exception);

Upvotes: 23

Dzmitry
Dzmitry

Reputation: 1471

There is an undocumented feature in Log4j 2 (and SLF4J 1.6+). One can pass Throwable as the very last parameter. And it would then get a special treatment. See AbstractLogger#logMessage(String, Level, Marker, String, Object...) and ReusableParameterizedMessage#initThrowable().

There is no need to bother with ParametrizedMessage. The code in the question will work just as expected:

logger.error("Logging in user {} with birthday {}", user.getName(), user.getBirthdayCalendar(), exception);

Upvotes: 105

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