Optimizing program logging: Sharing tips on setting log4j log levels

Optimize program logging: share log4j log level setting tips

Abstract: Program logging plays a key role in troubleshooting, performance tuning, and system monitoring. . This article will share tips on setting log4j log levels, including how to set different levels of logs and how to illustrate the setting process through code examples.

Introduction: In software development, logging is a very important task. By recording key information during the running process of the program, it can help developers find out the cause of the problem and perform performance optimization and system monitoring. Log4j is one of the most commonly used logging tools in Java and is flexible and efficient. Properly setting the logging level can improve program operation efficiency and reduce log size.

1. Introduction
   Before we start discussing log level settings, let us first understand what log levels are. Log level defines the priority of log information. Log4j provides 6 levels, from low to high, they are TRACE, DEBUG, INFO, WARN, ERROR and FATAL. Different levels are suitable for different scenarios, and we can flexibly set them according to needs.
2. Set log level
   2.1 Set the log level in the log4j.properties configuration file:

log4j.rootLogger=DEBUG, console
log4j.logger.com.example=INFO
log4j.logger.org.springframework=WARN

• rootLogger: Root logger, which can be set to any level.
• com.example: Logging rules under the specified package can be set to different levels.
• org.springframework: Set the log level of Spring framework.

2.2 Set the log level programmatically:

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class Log4jLevelSettingExample {
    private static final Logger logger = Logger.getLogger(Log4jLevelSettingExample.class);
    
    public static void main(String[] args) {
        logger.setLevel(Level.INFO);
        logger.debug("This debug message will not be printed.");
        logger.info("This info message will be printed.");
    }
}

3. Selection and suggestions of log level
   3.1 TRACE and DEBUG levels: generally used for troubleshooting and debugging phases , output a large amount of detailed debugging information. These two levels should be avoided in formal production environments to avoid excessive log size and affecting program performance.

3.2 INFO level: Record key information about program operation, such as start, stop, restart and other events, as well as key indicators of business operation data. This level is generally recommended for production environments.

3.3 WARN level: Record potential problems, but will not affect the normal operation of the program. Warning messages should draw the developer's attention, and further investigation may be required.

3.4 ERROR and FATAL levels: Record serious errors and fatal errors that may cause the program to crash or fail to work properly. These two levels should be avoided as much as possible, but when an exception occurs in the program, the error log can be output to troubleshoot the problem.

4. Dynamic modification of log level
   Sometimes, we need to dynamically modify the log level while the program is running in order to quickly adjust the log output. This can be achieved by using log4j's configuration API.

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class Log4jDynamicLevelExample {
    private static final Logger logger = Logger.getLogger(Log4jDynamicLevelExample.class);
    
    public static void main(String[] args) {
        logger.setLevel(Level.INFO);
        logger.debug("This debug message will not be printed.");
        logger.info("This info message will be printed.");
        
        // 修改日志级别
        Logger.getRootLogger().setLevel(Level.DEBUG);
        
        logger.debug("This debug message will be printed now.");
        logger.info("This info message will be printed now.");
    }
}

5. Summary
   Optimizer logging is very important for developers. Properly setting the log level can reduce the amount of log output and improve system performance. This article introduces the log level setting skills of log4j and illustrates the setting process through code examples. I hope readers can skillfully use these techniques to optimize program logging as needed in actual development.

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