How Java uses Log4j2 to record logs
Log4j2 is a logging framework in Java that can be used to record log information during application runtime. It is part of the Apache Logging Services project and an upgraded version of the Log4j framework, providing better performance and flexibility.
Some features of Log4j2 include:
1. High performance: Log4j2 has higher throughput and lower latency compared to Log4j 1. x.
2. Flexible configuration: Support configuration through XML, JSON, and other methods, and can configure different log levels, output targets, log rolling strategies, etc.
3. Multiple output targets: Support output to various targets such as console, file, remote server, etc.
4. Custom Appender: You can extend the log output function by implementing a custom Appender.
5. Asynchronous logging: Support the use of asynchronous logging to improve application performance.
The commonly used key classes and methods are as follows:
1. Logger: Logger is the core class of Log4j2, used to record logs. You can obtain the Logger object through the Logger. getLogger (String name) method. When outputting logs, different logging levels (such as ERROR, DEBUG, INFO, etc.) can be used to call different methods of Logger (such as error, debug, info, etc.).
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class MyClass {
private static final Logger logger = LogManager.getLogger(MyClass.class);
public void myMethod() {
logger.debug("Debug message");
logger.info("Info message");
logger.error("Error message");
}
}
2. LoggerContext: LoggerContext is used to obtain and configure the context information of Log4j2. The current LoggerContext object can be obtained through the LoggerContext. getContext() method.
3. Configuration: Configuration is used to configure the properties and settings of Log4j2. You can build and configure a Configuration object through the ConfigurationBuilder class.
4. Appender: Appender is an interface used to define log output targets. Log4j2 provides multiple built-in Appender implementations, such as ConsoleAppender (output to console), FileAppender (output to file), and so on.
5. Layout: The interface used by Layout to format log messages. Log4j2 also provides multiple built-in Layout implementations, such as PatternLayout (outputting logs according to specified patterns).
If Log4j2 is needed, the following Maven dependencies can be added to the pom.xml file:
<dependencies>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.14.1</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.14.1</version>
</dependency>
</dependencies>
At the same time, it is necessary to configure the relevant properties and settings of Log4j2 in the application's configuration file (such as log4j2. xml).
The above is a brief introduction to Log4j2 and sample code for commonly used methods. For specific usage and configuration methods, please refer to the official documentation of Log4j2.
