Hi Fabio, Thank you for the great question. In the SLF4J 1.7 series, the intended behavior is to treat the last parameter as an exception if it is of type Throwable. In addition, in 2.0 and going forward, if the exception is passed explicitly (via the fluent API), then the type of the last argument does not matter (it will seen as a value and not an exception). HTH, On 14.11.2019 14:17, Fabio Cechinel Veronez wrote:
Hello all,
I have a question regarding the behavior of an exception as last parameter.
It is very well known that an exception placed as last parameter will have a special handling, having its stack trace printed available in the final output. Ex:
``` logger.warn("Printing a value {} with exception's stacktrace", 23, new Exception("some message")); ```
Outputs something like:
``` 11:35:01.696 [main] WARN App - Printing a value 23 with exception's stacktrace java.lang.Exception: some message at App.main(App.java:7) ~[classes/:na] ```
My question is: what if the message string contains an interpolation expression for that exception parameter? Example:
``` logger.warn("Printing a value {} with an inlined exception {}", 23, new Exception("some message")); ```
Personally I would expect that in this case the exception would be printed just like any other regular parameter, not having its stracktrace printed. Basically, I would expected an exception to have a special handling only when it is the "+1" parameter.
It seems to have been the case up to logback-classic:1.0.13 (slf4j-api:1.7.5). Using this version the log statement above prints:
``` 11:35:01.699 [main] WARN App - Printing a value 23 with an inlined exception java.lang.Exception: some message ```
While using logback-classic:1.2.3 (slf4j-api:1.7.25) it prints:
``` 11:38:02.150 [main] WARN App - Printing a value 23 with an inlined exception {} java.lang.Exception: some message at App.main(App.java:8) ```
Apparently the behaviour changed from logback:1.1.0 onwards.
Is this a new expected behavior?
Unfortunately I couldn't find in the documentation where the expected behavior of this particular situation is explained in more details. So I thought it to be a bit ambiguous. If there one, please, let me know.
Thanks in advance.
-- -- Ceki Gülcü