Log4j dynamic loading configuration file

Application scenarios and problems

When the project is running , If we need to modify log4j 1.X perhaps log4j2 Configuration file for , Generally speaking, we cannot directly stop the project and then modify the file for redeployment . So there is such a problem ： How to do this without stopping the current project , Let the system automatically monitor the modification status of the configuration file , So as to realize the function of dynamically loading configuration files ？ and log4j 1.X and log4j2 The difference is slightly larger , How should they realize this function ？

log4j 1.X Load configuration files dynamically

log4j 1.X Provides a method to dynamically load configuration files ：

DOMConfigurator.configureAndWatch()
PropertyConfigurator.onfigureAndWatch()

DOMConfigurator The corresponding is xml The configuration file ,PropertyConfigurator The corresponding is properties The configuration file . Both classes have configureAndWatch This method , This method has an overloaded method , as follows ：

configureAndWatch(String configFilename)
configureAndWatch(String configFilename, long delay)

configureAndWatch Method is used to monitor whether the configuration file has been changed , The monitoring interval is delay Parameters to determine , If this parameter is not passed in, the default time interval is used 1 minute (60000L).configureAndWatch(String configFilename) It's actually called configureAndWatch(String configFilename, long delay).

Code example ：

import org.springframework.util.ResourceUtils;
import org.springframework.util.SystemPropertyUtils;
import org.apache.log4j.PropertyConfigurator;

try {
    
    String resolvedLocation = SystemPropertyUtils.resolvePlaceholders("classpath:log4j.properties");
    File file = ResourceUtils.getFile(resolvedLocation);
    if (file.exists()) {
    
        PropertyConfigurator.configureAndWatch(file.getAbsolutePath(), TimeUnit.SECONDS.toMillis(5));
    } else {
    
        LOGGER.error("classpath:log4j.properties");
    }
} catch (Exception e) {
    
    LOGGER.error(" Turn on log4j Error in log monitoring ", e);
}

log4j2 Load configuration files dynamically

and log4j 1.X Compare to ,log4j2 The dynamic loading configuration of is very simple , There is no need to call api, The method is as follows ：

<configuration monitorInterval="30">
    ...
</configuration>

stay log4j2.xml In the configuration file configuration Node add monitorInterval Value , The unit is seconds , If the configured value is greater than 0, It will automatically scan whether the configuration file has been modified according to the time interval , And reload the latest configuration file after modification . If this value is not configured , The default is 0, That is, do not scan whether the configuration file has been modified .

Reference article

The underlying implementation principle of dynamically loading configuration files watchDog
https://www.cnblogs.com/yulinlewis/p/10177196.html