Explanation of log4j and configuration of log4j.properties

2 years ago

Benjamin Taylor

2 minutes

log4j is a Java logging framework that can be used to log information in an application. It supports different log levels, log output destinations, and formatting options. log4j.properties is a configuration file used to set up the behavior of the log4j framework. Here is an explanation of an example log4j.properties configuration file: 1. Set the root log level:

log4j.rootLogger=level

This configuration item is used to set the level of the root log, which can be one of the following values: ALL, DEBUG, INFO, WARN, ERROR, FATAL, OFF. The root log level determines the minimum level for all logs. 2. Set the log output target:

log4j.appender.appenderName=className

This configuration setting is used to set the output destination for logs, which can be one of the following values: Console, File, RollingFile, DailyRollingFile, Socket, JDBC, etc. Where appenderName is a custom output destination name, and className is the corresponding class name for the output destination.3. Set the log output format:

log4j.appender.appenderName.layout=className

This configuration setting is used to determine the format of the output logs, which can be one of the following values: PatternLayout, HTMLLayout, SimpleLayout, XMLLayout, etc. In this case, appenderName refers to the name of the output destination, and className refers to the class name for the corresponding output format. Step 4 is to set the log level:

log4j.logger.loggerName=level

This configuration setting is used to specify the level of a particular logger, which can be one of the following values: ALL, DEBUG, INFO, WARN, ERROR, FATAL, OFF. Here, loggerName is a custom logger name. 5. Setting the log output destination and format:

log4j.logger.loggerName.appender.appenderName=level

This configuration item is used to set the output target and format for a specified logger, where loggerName is the logger’s name, appenderName is the output target’s name, and level is the log level. 6. Set the log file path:

log4j.appender.appenderName.File=filePath

This configuration setting is used to specify the file path for logging output when the output target is a file. Here, appenderName refers to the output target name, and filePath refers to the file path. The above are some commonly used configuration options in the log4j.properties file and their explanations. These configurations can be adjusted as needed to meet the logging requirements of the application.