How can logback dynamically switch log levels?

Logback allows for dynamically changing the log level in the configuration file to achieve dynamic logging level switching. The specific steps are as follows:

1. In the logback.xml configuration file, use variables (such as ${log.level}) to specify the log level. For example:

<root level="${log.level}">
    ...
</root>

1. In the code, variables can be modified by obtaining the LoggerContext object. For example:

LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
loggerContext.putProperty("log.level", "DEBUG");

1. To change the log level, modify the value of the variable by calling the code in step 2.

It is important to note that dynamic switching of log levels requires the logback.xml configuration file to be reloaded after any modifications in order for the new log levels to take effect. This can be achieved by calling the loggerContext.reset() method to reload the configuration file. For example:

loggerContext.reset();

Additionally, you can also utilize JMX (Java Management Extensions) to achieve dynamic switching of log levels. With JMX, you can modify logback configurations at runtime through a JMX client, enabling dynamic switching of log levels.