Structure and parameter analysis of log4j configuration file

Structure and parameter analysis of log4j configuration file

[Introduction]
In software development, logs are a very important tool that can help developers Record key information and error information during the operation for troubleshooting and analysis when necessary. Log4j is a commonly used Java logging framework. It provides powerful logging functions to facilitate log management and debugging for developers. This article will introduce the structure and parameter analysis of the log4j configuration file, and provide specific code examples.

[Structure of log4j configuration file]
The log4j configuration file adopts .properties or .xml file format and is used to define the behavior of log4j. The following is the structure of a typical log4j configuration file:

1. Root Logger

log4j.rootLogger=[level], [appender1], [appender2]...

rootLogger is the root Logger of log4j, and all log output will pass through here. [level] indicates the log level of the root Logger. Commonly used ones include DEBUG, INFO, WARN, ERROR, and FATAL. [appender1] and [appender2] represent additional Appenders, and there can be multiple.

2. Logger

log4j.logger.[package]=[level], [appender1], [appender2]...

Logger is log4j A logger used to control logging for a specific package or class. [package] represents the name of the package or class, [level] represents the log level of the Logger, which can be set to inheritance or disabled. [appender1] and [appender2] represent additional Appenders, and there can be multiple.

3. Appender

log4j.appender.[name]=[class]

Appender is the log output target of log4j, used to determine the log output Destination and means. [name] represents the name of the Appender, and [class] represents the implementation class of the Appender.

4. Layout

log4j.appender.[name].layout=[class]

Layout is the log layout of log4j, used to control log output format. [name] represents the name of the Appender, and [class] represents the implementation class of Layout.

[Parameter analysis and sample code]
The following are commonly used log4j configuration file parameters and their parsing instructions, and provide specific code examples:

1. Log level

log4j.rootLogger=DEBUG

means setting the log level of the root Logger to DEBUG, which means that all log information will be output.

2. Output to console

log4j.appender.console=org.apache.log4j.ConsoleAppender

Indicates using ConsoleAppender as the output target, that is, log Information is output to the console.

3. Output to file

log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=log.log
log4j.appender.file.ImmediateFlush=true

means using FileAppender as the output target and outputting log information to the file log.log. ImmediateFlush is set to true to write information to the file immediately.

4. Output to log file and perform date cutting

log4j.appender.daily=org.apache.log4j.DailyRollingFileAppender
log4j.appender.daily.File= log.log
log4j.appender.daily.DatePattern='.'yyyy-MM-dd

means using DailyRollingFileAppender as the output target and outputting the log information to the log.log file. DatePattern is set to '.'yyyy-MM-dd means that a new log file will be generated every day, with date as the suffix.

5. Output to different files according to the log level

log4j.appender.debug=org.apache.log4j.RollingFileAppender
log4j.appender.debug.File=debug .log
log4j.appender.debug.Threshold=DEBUG

log4j.appender.error=org.apache.log4j.RollingFileAppender
log4j.appender.error.File=error.log
log4j.appender.error.Threshold=ERROR

means that the log information will be output to the debug.log and error.log files respectively according to the log level. Setting Threshold to DEBUG and ERROR respectively means that only log information of the corresponding level and above will be output.

[Summary]
This article introduces the structure and parameter analysis of the log4j configuration file, and provides specific code examples. As a mature and stable logging framework, log4j provides developers with powerful logging and management functions. Properly configuring the log level and output target of log4j can help developers quickly locate problems and debug, and improve development efficiency.

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