Common problems and errors to solve the Apache Log4j Core framework (Common Ises and Erruche Log4j Core Framework)

Apache Log4J Core framework is a popular Java log record scheme.However, when using log4j core, some common problems and errors may be encountered.This article will introduce some common problems and provide solutions and corresponding Java code examples. Question 1: The log output is not displayed or confused When using Log4J Core, sometimes the log message is not displayed, or the order of the display is chaotic.This is usually caused by the correct setting of the configuration file.To solve this problem, you can follow the steps below: Step 1: Make sure the log4j2.xml configuration file is located under the class path. Step 2: Check whether the output target in the configuration file is set correctly. Step 3: Check whether the log level is set correctly.If a higher level (such as ERROR) is set, the log message of the low level (such as INFO) will not be displayed. Step 4: Verify whether the loger defined in the configuration file is correctly matched the logger in the code. The following is an example of the log4j2.xml configuration file to output the log to the console. <?xml version="1.0" encoding="UTF-8"?> <Configuration status="WARN"> <Appenders> <Console name="Console" target="SYSTEM_OUT"> <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" /> </Console> </Appenders> <Loggers> <Root level="info"> <AppenderRef ref="Console" /> </Root> </Loggers> </Configuration> Question 2: The configuration file cannot be loaded Sometimes, when the application starts, the log4j core cannot load the configuration file.This is usually due to the position of the configuration file or the incorrect name.Make sure the following points: 1. Configure file (such as log4j2.xml) is located under the class path. 2. The name and extension of the configuration file are correct, and they are consistent with the name referenced in the code. Here are a code fragment of an example to demonstrate how to manually load the log4j core configuration file. import org.apache.logging.log4j.core.config.Configurator; public class Application { public static void main(String[] args) { Configurator.initialize(null, "log4j2.xml"); // Your application code here } } Question 3: Contains unnecessary log message in the console output Sometimes, the output of the LOG4J Core console contains some unnecessary log messages, such as some logs generated inside the framework.To solve this problem, you can exclude unnecessary log messages, and only output the log we are interested in. Here are a example of the log4j2.xml configuration file, which only prints the log message from the application code. <?xml version="1.0" encoding="UTF-8"?> <Configuration status="WARN"> <Appenders> <Console name="Console" target="SYSTEM_OUT"> <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" /> </Console> </Appenders> <Loggers> <Root level="info"> <AppenderRef ref="Console" /> </Root> <Logger name="org.some.library" level="off" additivity="false"> <AppenderRef ref="Console" /> </Logger> </Loggers> </Configuration> The above are some common problems and errors in the Apache Log4J Core framework, as well as the corresponding solutions and Java code examples.Hope to help you better use the log4j core record and management log information.