How do you control the log level of a single log file in log4j?

In log4j, the log level for a single file can be controlled through a configuration file or through code.

1. Open the configuration file for log4j (typically log4j.properties or log4j.xml) and locate the appender for which you want to modify the log level. Then, add a Threshold attribute to the appender configuration and set the log level. For example, to set the log level of a file named mylogger.log to DEBUG, you can add the following configuration.
2. Set the log level for myAppender to DEBUG and specify the logging output file as mylogger.log.
3. In Java code, you can use the Logger.getLogger method to obtain the Logger object whose log level needs to be modified, and then use the setLevel method to set the log level. For example, to set the log level of a file named mylogger.log to DEBUG, you can use the following code:
4. Declare a logger object for the class “MyClass” in the package “com.example” and set its logging level to DEBUG.
5. Please replace “com.example.MyClass” with the actual Logger name in the code above.

Ensure that the log level set, whether in the configuration file or in the code, is valid and takes effect along with other configuration options.