The log level and how to use the "Logger" framework

The log level and how to use the "Logger" framework In software development, logs are a way to record important information when the application is running.Use logs can easily track and debug applications and help developers identify potential problems.For this reason, many programming languages and frameworks provide the function of logging.In Java, one of the most commonly used log frames is "Logger".This article will introduce the log level and its usage methods in the logger framework in detail. 1. Log level The Logger framework provides different logs to capture appropriate information according to the importance of the log and urgency.The following is the standard log level defined in the logger framework: -Old (all logs) -Trace (tracking details) -DEBUG (debugging information) -INFO (General Information) -WARN (Warning Information) -ERROR (error message) -FATAL (serious error) -Off (disable all logs) These log levels are arranged in order from low to high, and each level contains all the log information of all previous levels.For example, if the log level is set to INFO, it will record the log information of all INFO levels and above (Warn, ERROR, FATAL). 2. Logger class When using the Logger framework, you need to use the logger class to record the log message.The Logger class is the core component of the Logger framework and is responsible for creating and managing logs.You can record the log messages of different levels by obtaining the Logger instance and using its method. The following is an example code that uses the logger framework to record log messages: import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; public class MyClass { // Get Logger instance private static final Logger logger = LogManager.getLogger(MyClass.class); public void myMethod() { // Use different levels of log messages logger.trace("This is a TRACE log message"); logger.debug("This is a DEBUG log message"); logger.info("This is an INFO log message"); logger.warn("This is a WARN log message"); logger.error("This is an ERROR log message"); logger.fatal("This is a FATAL log message"); } } In the above example code, first use the `logmanager.getLogger () method to obtain the logger instance.You can then use different methods of Logger instances to record different levels of log messages.Each method accepts a string parameter as a log message that needs to be recorded. 3. Configuration log level The Logger framework also allows the log level through configuration files.You can create a configuration file called "log4j2.xml" or "log4j2.properties" to set the log level.Through the configuration file, the log level can be flexibly changed without re -compiling the code. The following is a simple "log4j2.xml" configuration file example: <?xml version="1.0" encoding="UTF-8"?> <Configuration> <Appenders> <Console name="Console" target="SYSTEM_OUT"> <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" /> </Console> </Appenders> <Loggers> <Logger name="com.example" level="DEBUG" additivity="false"> <AppenderRef ref="Console" /> </Logger> <Root level="ERROR"> <AppenderRef ref="Console" /> </Root> </Loggers> </Configuration> In the above examples, the log level is configured as Debug.For the category under the `Com.example` package, the log message will be recorded and above.For other categories, the log message of ERROR level and above will be recorded.This can be configured according to your own needs, and can change the log level at any time in order to dynamically control the output of the log. Summarize: The Logger framework is a commonly used tool for application records and management log information in Java.Through different log levels, the log messages that can be easily controlled.Using the Logger class, you can record log messages at different levels, and set a flexible log -level settings through configuration files.Mastering the use of the Logger framework helps developers to track and debug applications more easily, increasing the maintenance and reliability of the code. I hope this article will help you understand the log level in the logger framework and its usage method.