Should logs that use ParameterizedMessage support trailing throwables? The
ParameterizedMessage code identifies throwables in the argument array, but they
are silently ignored. This is for methods like:
void info(String message, Object... params);
Example:
log4j2Logger.info("log4j2Logger no params with throwable?", t); // works
log4j2Logger.info("log4j2Logger {}", "params with throwable?", t); // fails
Output:
2011-09-15 11:55:40,497 INFO Log4j2Testing [main] log4j2Logger no params with
throwable?
java.lang.Throwable
at Log4j2Testing.main(Log4j2Testing.java:18)
2011-09-15 11:55:40,499 INFO Log4j2Testing [main] log4j2Logger params with
throwable?
On a related note, consider Logger methods like the following:
void info(Message msg);
void info(Message msg, Throwable t);
If Message objects support Throwables, as may be true for ParameterizedMessage
or future message types (end user created or new to be conceived log4j2
standard messages), there is ambiguity in the second method as to which
throwable is "the" throwable. Perhaps the first non-null, or maybe the
explicit argument overrides the msg throwable. In any case, it is a bit
confusing.
Perhaps the second method with an explicit Throwable should be eliminated, and
Message objects should support Throwables when desired. getThrowable() could
be added to the Message interface, or even a separate MessageWithThrowable
interface similar to the way FormattedMessage works. (The former may be better
to avoid having too many interfaces and instanceof clutter.)
It seems to me that throwables are a natural part of messages, just as the
formatted message strings and parameters are.
It doesn't look like adding throwables to Messages would cause additional
overhead. In cases like ParameterizedMessage, it standardizes the approach to
throwables and gives the Message object more power. In other cases, it just
changes the location of a parenthesis in the code:
public void info(String message, Throwable t) {
if (isEnabled(Level.INFO, null, message, t)) {
log(null, getFQCN(), Level.INFO, new SimpleMessage(message), t);
}
}
becomes:
...
log(null, getFQCN(), Level.INFO, new SimpleMessage(message, t));
...
John
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