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
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