Re: [xwiki-devs] [Proposal] Java logging best practices additions

Hi devs, On http://dev.xwiki.org/xwiki/bin/view/Community/JavaCodeStyle#HLoggingBestPra… we have some best practices defined for logging. I’d like to propose some additions. Best practices: * Use SLF4J * If you’re in a component get the logger injected using @Inject private Logger logger otherwise use: private static final Logger LOGGER = LoggerFactory.getLogger(My.class); * Use logger.info() when it’s absolutely necessary for the user to see the message in the logs. Usually only used at startup and we want to limit what the user sees to the absolute necessary to avoid swamping him. * Use logger.warning() when an error happens but it doesn’t compromise the stability and general working of an XWiki instance. A warning just shows the user that something has gone wrong and it should provide him with as much information as possible to solve the issue. Do not print a stack trace when you output a warning since stack traces fill the logs and should be reserved for errors. In the view of users stack traces are synonymous with errors. We want it to be easy for admins to visually check the log files and see important problems (ie errors). * Use logger.error() when there’s an important problem that compromises the stability of the XWiki instance or that prevent an important system from working and that should not have happened. Always pass a stack trace when logging errors since it’s something that shouldn’t have happened an a developer will need to debug the problem to fix it. * Always log as much information as possible to make it easier to understand what’s going on. * Surround parameters with “[]” in order to separate visually the text from the parameters and also clearly notice when leading/trailing spaces are located in parameters. * For improved performances, always use the vararg signature of SLF4J for logging parameters and do not concatenate them manually: this.logger.debug("Test message with [{}] and [{}]", param1, param2); vs this.logger.debug("Test message with [“ + param1 + "] and [“ + param2 + “]", param1, param2); * When logging a warning, we don’t want to log the full stack trace but it’s still interesting from time to time to display the root issue. If you do the following you won’t get the root issue: LOGGER.warn("Failed to determine if the index exists: [{}]. Trying to recreate the index..”, e.getMessage()); Instead use ExceptionUtils from commons lang: LOGGER.warn("Failed to determine if the index exists: [{}]. Trying to recreate the index..”, ExceptionUtils.getRootCauseMessage(e)); WDYT? Thanks -Vincent