Logging

[ChristianGruen]

Send stdout and stderr output to loggers, such as Log4J. If no loggers are found, output should stay as is.

[ChristianGruen]

Issues to solve:

• If the BaseX command-line interfaces are run (basex, basexclient, basexgui?), output should probably always be directed to standard out/err. This could e.g. be solved by an additional flag that indicates if loggers should be ignored.
• Things are getting difficult with basexserver, which can both be run as service and as interactive tool (via -i).

[mgaerber]

Since BaseX usage can not (and maybe better should not) predicted (lib vs tool vs dbms...), I propose adding hooks or annotations so it would be possible to introduce such functionality on another level. E.g. aspectj could be one way of allowing different "flavors".

[ghost]

Rergarding the .logs directory in the GUI, i wonder why there are no entries appearing when execution a (HTTP) query? is there anything to set?

[BenoitMaisonny]

I don't really see why some BaseX applications should write to the console: BaseX is not a small command-line tool. Are there other tools that depend on this console output? Using System.err/out is discouraged, except of course for pure command-line tools.

Would anyone really need console output, Log4J (and probably other loggers as well) can be configured to log to standard error/output.

The opposite, redirecting System.err/out to a logger, is possible also, so it's not a big deal and it's quite understandable if BaseX developers find more interesting issues to tackle ;-) It looks like System.err/out is only used in org.basex.util.Util, in 2 places, so I can propose a patch if you are interested.

My problem with BaseX writing to System.err is that a BaseX message is sometimes output in the middle of a log message when the logger outputs to the console. Context: BaseXServer embedded in a Java application, running as a JUnit unit test within Eclipse. I suppose it would not be a problem in a real application.

[ChristianGruen]

Hi @BenoitMaisonny, thanks for your offer; pull requests are always welcome. I guess one challenge will be to preserve the CLI features of BaseX (i.e. to decide when output to stdout is appropriate and when not).