slf4j: how to log formatted message, object array, exception

Question

What is the correct approach to log both a populated message and a stack trace of the exception?

logger.error(
    "\ncontext info one two three: {} {} {}\n",
    new Object[] {"1", "2", "3"},
    new Exception("something went wrong"));

I'd like to produce an output similar to this:

context info one two three: 1 2 3
java.lang.Exception: something went wrong
stacktrace 0
stacktrace 1
stacktrace ...

slf4j version 1.6.1

Answer 1

As of SLF4J 1.6.0, in the presence of multiple parameters and if the last argument in a logging statement is an exception, then SLF4J will presume that the user wants the last argument to be treated as an exception and not a simple parameter. See also the relevant FAQ entry .

So, writing (in SLF4J version 1.7.x and later)

 logger.error("one two three: {} {} {}", "a", "b", 
              "c", new Exception("something went wrong"));

or writing (in SLF4J version 1.6.x)

 logger.error("one two three: {} {} {}", new Object[] {"a", "b", 
              "c", new Exception("something went wrong")});

will yield

one two three: a b c
java.lang.Exception: something went wrong
    at Example.main(Example.java:13)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at ...

The exact output will depend on the underlying framework (eg logback, log4j, etc) as well on how the underlying framework is configured. However, if the last parameter is an exception it will be interpreted as such regardless of the underlying framework.

Answer 2

In addition to @Ceki 's answer, If you are using logback and setup a config file in your project (usually logback.xml), you can define the log to plot the stack trace as well using

<encoder>
    <pattern>%date |%-5level| [%thread] [%file:%line] - %msg%n%ex{full}</pattern> 
</encoder>

the %ex in pattern is what makes the difference

Answer 3

The accepted answer is great. I'm just adding here my case that is now working thanks for the answer. This may help someone else.

I'm using SLF4J and logback with a JSON encoder. Furthermore, I use marker and arguments to enrich my output.

    logger.error(getMarker("errorEvent"),
                 "An error occurred",
                 entries(mapOf("someKey" to "someValue")),
                 new Exception())

The output:

{
   "level": "ERROR",
   "event": "errorEvent",
   "eventData": {
      "someKey": "someValue"
   },
   "stacktrace": "...omitted...",
   "message": "An error occurred"
}

Of course there is a lot of configuration of logstash behind the scenes, but I just wanted to show that the arguments passed as entries are shown in the configured eventData tag.