The working principle analysis of the Apache Log4J Web framework in the Java class library
Apache Log4j is a powerful Java log record tool, which is widely used in the Web framework.This article will analyze the working principle of the Apache Log4J Web framework, including its complete programming code and related configuration.
1. Overview of work principles
The core principle of the Apache Log4J Web framework is to write and manage the logs of web applications through configuration and code.It mainly includes the following aspects:
1. Configuration file: First of all, you need to write the configuration file of log4j, which is usually named "log4j2.xml".The configuration file defines information such as the level of log records, output destinations, and log formats.
2. Dependence adding: In the construction file of the project, add dependence on the log4j web framework.You can use Maven, Gradle and other construction tools to declare the dependence on the LOG4J Web framework in the configuration file of the project.
3. Introduce code: In the related class of web applications, the class library and related methods of log4j are introduced to realize the call of log records.
4. Configuration initialization: During the startup process of the web application, the initialization of log4j is performed through the configuration mechanism of the web framework.You can initialize the configuration during the application through the server, filter, or Spring framework.
5. Logging: Use the API provided by log4j in the code. Select the appropriate log level as needed, and pass the log information to the recorded to the log4j framework.The log4j framework will output log information to file, console or database, according to the output destination defined in the configuration file.
2. Example code and configuration analysis
In order to better understand the working principle of the Apache Log4J Web framework, a simple example code and configuration file are provided below.
Example code:
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class ExampleClass {
private static final Logger logger = LogManager.getLogger(ExampleClass.class);
public void method() {
logger.trace("Trace level log message");
logger.debug("Debug level log message");
logger.info("Info level log message");
logger.warn("Warning level log message");
logger.error("Error level log message");
logger.fatal("Fatal level log message");
}
}
Configure the file "log4j2.xml":
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
<Appenders>
<Console name="Console" target="SYSTEM_OUT">
<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
</Console>
<File name="File" fileName="logs/application.log">
<PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
</File>
</Appenders>
<Loggers>
<Root level="debug">
<AppenderRef ref="Console"/>
<AppenderRef ref="File"/>
</Root>
</Loggers>
</Configuration>
The above example code defines a class called "ExampleClass", which contains a method "Method".In this method, use log4j Logger objects to record log information of different levels.
The configuration file defines two APENDER (output destinations): one is Console (output to the console), the other is FILE (output to the specified file), and the log output format is set.Two APPENER is referenced to the root logger through the root label.
When the application is running, the log information will be output to the file specified by the File Appender according to the settings in the configuration file, and it is displayed on the console.
3. Summary
The Apache Log4J Web framework is written in configuration files and code to implement log records and management of Web applications.Through reasonable configuration and calling LOG4J API, the records and output of log information of different levels can be achieved.
I hope this article can help everyone understand the working principle of the Apache Log4J Web framework and be able to configure and use log4j correctly in the project.If you have any questions, please leave a message to discuss.
