SLF4J API module: How to configure and adjust log level

SLF4J (Simple Logging Facade for Java) is a simple and uniform interface to implement logging facade in the Java application.It provides a universal log abstraction layer that allows developers to switch between different log frames without having to modify the code of the application. The SLF4J itself does not realize any log function, but instead entrusts the log to the log framework for the bottom layer, such as logback, log4j or java.util.logging.By using SLF4J, we can realize the unified configuration and management of log output, thereby simplifying the maintenance and upgrading of the log system. In SLF4J, logging level is used to describe the importance of log messages.Depending on the severity, SLF4J provides multiple log level options, including: 1. Trace: The lowest level, used to output the most detailed debugging information, is usually used only in the development and debugging phase. 2. Debug: Debugging level, for output debugging information, which is very useful for investigating problems and analysis program flows. 3. Info: Information level, information used for the normal runtime of the output program, such as starting information, processing requests, etc. 4. Warn: The warning level is used to output some warning information that may cause problems, but it will not affect the normal operation of the program. 5. ERROR: Error level, for output program information when error occurs, such as abnormalities, errors, etc. To configure and adjust the log level of SLF4J, you need to understand three aspects: SLF4J's binding framework configuration, the use of log facade API, and specific log implementation framework configuration. First, the log implementation framework (such as LOGBACK) in SLF4J usually needs to be configured.Through configuration files, we can specify log levels, output formats, target output positions, etc.The position and format of the configuration file varies from the framework to the specific log implementation framework. It is generally stored in the root directory or resource directory of the project.Below is an example of a logback configuration file: <configuration> <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender"> <encoder> <pattern>%date{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern> </encoder> </appender> <root level="INFO"> <appender-ref ref="CONSOLE" /> </root> </configuration> The above configuration sets the log level to INFO and outputs it to the console.You can adjust the log level and output method according to your needs. Next, in order to use SLF4J in the code for log records, the relevant dependencies need to be imported, as shown below: <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.30</version> </dependency> In the code, we can record the log through the Logger interface of the SLF4J.Usually, each class uses a logger instance, which can be defined at the top of the class: import org.slf4j.Logger; import org.slf4j.LoggerFactory; public class MyClass { private static final Logger logger = LoggerFactory.getLogger(MyClass.class); public void doSomething() { logger.info("Doing something..."); // ... } } In the above example, we obtain the Logger instance of `myclass` and use the` Info () "method to record a message.Choose different log -level methods according to the actual situation, such as `Trace ()`, `debug (),` warn () or `eerror ()`. Finally, if you need to adjust the log level, you only need to modify the `Root Level =" Info "> line in the configuration file of the binding framework to change it to the required level.Restart the application to take effect. In summary, the configuration file of the framework is implemented by the configuration log, and the SLF4J dependencies and the use of the Logger interface to record logs can easily perform the log level configuration and adjustment of the SLF4J API module.This flexibility and scalability make SLF4J a widely used log abstraction layer in Java development.