log4j defines eight levels of log (and remove OFF ALL can be said to be divided into six levels), * priority of the descending order: OFF FATAL ERROR WARN INFO DEBUG the TRACE ALL * * ALL lowest level for all open logging * the TRACE low log level generally do not use the * dEBUG pointed out that fine-grained information events for debugging applications are very helpful in the development process is mainly used to print some operational information * iNFO messages on a coarse-grained level to highlight applications the process of running the program * print some of your interesting or important information that can be used for some important information output production environments running * but not abuse avoid printing too many logs * WARN indicates a potential error situation that some information will appear not an error message but also to give some tips programmers * eRROR error pointed out that although the incident but still does not affect the continued operation of the system * print error and exception information you do not want too many logs can be output using this level * FATAL pointed out that every serious the error occurs if exiting the application * the relatively high level of a major fault This level you can stop the program directly * OFF highest level for close all logging * * If the log level is set at a certain level so than this high level of priority log can be printed out * For example, if you set the priority for the WARN OFF FATAL ERROR WARN 4 log normal levels of output * and INFO DEBUG TRACE ALL log level is ignored ---------------- Disclaimer: This article is CSDN blogger "Shame Mo Yi" in original article, follow the CC 4.0 BY- SA copyright agreement, reproduced, please attach the original source link and this statement. Original link: HTTPS: // blog.csdn.net/qq_28289405/article/details/82982593