Detailed explanation of the log configuration file in the Apache Log4j framework
Apache Log4j is a log management tool for Java language. By configured log output, it can help developers to achieve flexible log records and management.In LOG4J, the output and level of the log can be flexibly controlled by configuration files.This article will introduce the log configuration files in the log4j framework in detail, and provide the necessary programming code and related configuration.
1. Configure file naming and position:
The configuration file of log4j is usually named log4j.properties or log4j.xml. You can choose one of the formats according to personal preference.The position of the configuration file can be placed in the root directory of the Java project, or under the class path (generally placed in the SRC/main/Resources directory).
2. Basic configuration format:
The log4j configuration file is configured in the form of key value pair.The following is an example of a simple log4j.properties configuration file:
# Set the log output level
log4j.rootLogger=INFO, stdout
# Console output configuration
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1}:%L - %m%n
# Set the log file output configuration
log4j.appender.file=org.apache.log4j.FileAppender
log4j.appender.file.File=/path/to/log/file.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} [%-5p] %c{1}:%L - %m%n
In the above examples, we first set up the output level of the log to Info, which means that only the INFO level and above logs will be output.Then, we define two output methods: console and log files.
3. Console output configuration:
In the above example, through log4j.appender.stdout configuration items, we define a console output called Stdout.Then, through the log4j.appender.stdout.Layout configuration item, we specify the output format to PatternLayout and set the output format mode.In the above examples,%d represents the date time, [%-5p] indicates the log level,%c {1} indicates the class name,%L represents the row number, and%m%n means the log message and change.
4. Log file output configuration:
In the above example, through log4j.appender.file configuration items, we define a log file output called File.Then, through log4j.appender.file.file configuration items, we designated the output path of the log file.Similar to the console output, through log4j.appender.file.Layout configuration items, we designated the output format as PatternLayout and set output format mode.
5. More configuration items:
In addition to the above configuration items, LOG4J also provides many other configuration items, which can be set as needed.For example, you can set the logging strategy (log4j.appender.file.rollingPolicy) to control the size and quantity of the log file; you can set the log 4j.appender.file.fileter to control the output conditions of the log.
6. Example code:
The following is a Java code example using log4j record log:
import org.apache.log4j.Logger;
public class MyClass {
private static final Logger logger = Logger.getLogger(MyClass.class);
public void doSomething() {
logger.debug("Debug message");
logger.info("Info message");
logger.warn("Warn message");
logger.error("Error message");
logger.fatal("Fatal message");
}
}
In the above example, we first obtain the logger object through the logger.getLogger method, and the parameter is passed into the current class name.Then, we can use different methods of the Logger object to record different levels of log messages.
Summarize:
Through the configuration file of the log4j framework, we can easily control the output and level of logs.The above example shows the format of how to configure the output of the console and the log file output.With the LOG4J API, we can easily record different levels of log messages in the application.In this way, we can easily track and debug the code to improve the maintenance and reliability of the application.
