Log4j 面试题与答案

问题 6. Explain why to use Apache Log4j.

• Apache log4j is an open-source and due to this, it's completely free to use.
• You can easily save log information into either files or even databases.
• Can be used for projects of any size small, medium, or large.

问题 7. What are the features of log4j?

The following are features of log4j:

• Log4j is thread-safe.
• It is optimized for speed.
• It is based on a named logger hierarchy.
• It supports multiple output appenders per logger.
• It supports internationalization.
• It is not restricted to a predefined set of facilities.
• Logging behavior can be set at runtime using a configuration file.
• It is designed to handle Java Exceptions from the start.
• It uses multiple levels, namely ALL, TRACE, DEBUG, INFO, WARN, ERROR, and FATAL.
• The format of the log output can be easily changed by extending the Layout class.
• The target of the log output as well as the writing strategy can be altered by implementations of the Appender interface.
• It is a fail-stop. However, although it certainly strives to ensure delivery, log4j does not guarantee that each log statement will be delivered to its destination.

问题 8. What are the two static methods for obtaining a logger object?

The two static methods in log4j for obtaining a logger object are:

• public static Logger getRootLogger()
• public static Logger getLogger(String name)

问题 9. How log4j file is defined?

Log4j file is defined by the name log4j.properties, it keeps properties in key-value pairs. By default, the log manager looks for a file name log4j.properties in the CLASSPATH.

问题 10. What is package-level logging in log4j?

Package level logging is the standard logging of log4j, with this we would determine the package and the associated level.