java - 我们可以在运行时更改 log4j 的日志记录级别吗

Question

我有一个问题，我想在运行时更改 log4j 的日志记录级别，我用 log4j.properties 文件尝试了很多事情，我还尝试编写一段代码，在特定时间后再次读取属性文件配置记录器。

但问题是，我想将一个 API 调用的日志记录级别更改为 DEBUG，然后当该调用完成时，记录器应再次更改为之前的值。

请帮忙..

Answer 1

调用 Logger.setLevel 方法与所需的 Level 可以改变 Logger运行时的输出电平。

下面是一个演示其用法的例子:

Logger logger = Logger.getLogger("myLogger");
logger.addAppender(new ConsoleAppender(new SimpleLayout()));

System.out.println("*** The current level will be INFO");

logger.setLevel(Level.INFO);
logger.warn("Only INFO and higher will appear");
logger.info("Only INFO and higher will appear");
logger.debug("Only INFO and higher will appear");

System.out.println("*** Changing level to DEBUG");

// remember the previous level
Level previousLevel = logger.getLevel();

logger.setLevel(Level.DEBUG);
logger.warn("DEBUG and higher will appear");
logger.info("DEBUG and higher will appear");
logger.debug("DEBUG and higher will appear");

System.out.println("*** Changing level back to previous level");

// revert to previous level
logger.setLevel(previousLevel);
logger.warn("Only INFO and higher will appear");
logger.info("Only INFO and higher will appear");
logger.debug("Only INFO and higher will appear");

以上输出:

*** The current level will be INFO
WARN - Only INFO and higher will appear
INFO - Only INFO and higher will appear
*** Changing level to DEBUG
WARN - DEBUG and higher will appear
INFO - DEBUG and higher will appear
DEBUG - DEBUG and higher will appear
*** Changing level back to previous level
WARN - Only INFO and higher will appear
INFO - Only INFO and higher will appear

上面演示了如何改变一个Logger的级别名为 myLogger , 但如果当前存储库中所有记录器的级别都应该更改，那么 setLevel通过 Logger.getRootLogger 获得的根记录器 上的方法应调用以更改所有子记录器的级别。