Spring Boot Log4j2.xml Example

Spring boot’s default logging uses Logback which is included as a transitive dependency. Spring Boot supports Log4j2 for logging configuration if it is on the classpath and Logback is excluded.

To configure Log4j2 with Spring Boot2, follow these two simple steps:

1. Log4j2 Maven Dependency

In fact, it is two steps change. First, remove spring’s default spring-boot-starter-logging starter dependency which excludes Logback from the classpath. Then add the spring-boot-starter-log4j2 starter dependency.

 <dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter</artifactId>
    <exclusions>
      <exclusion>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-logging</artifactId>
      </exclusion>
    </exclusions>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-log4j2</artifactId>
  </dependency>
</dependencies>

2. Add log4j2.xml File in /resources Folder

Spring will automatically configure log4j2 once it finds its jar files in the classpath. Now we have to add log4j2.xml or (log4j2.properties) in src/main/resources folder. That’s all.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" monitorInterval="30">
    <Properties>
        <Property name="LOG_PATTERN">%d{yyyy-MM-dd'T'HH:mm:ss.SSSZ} %p %m%n</Property>
        <Property name="APP_LOG_ROOT">c:/temp</Property>
    </Properties>

    <Appenders>
        <Console name="Console" target="SYSTEM_OUT" follow="true">
            <PatternLayout pattern="${LOG_PATTERN}" />
        </Console>
        <RollingFile name="appLog"
                fileName="${APP_LOG_ROOT}/SpringBoot2App/application.log"
                filePattern="${APP_LOG_ROOT}/SpringBoot2App/application-%d{yyyy-MM-dd}-%i.log">
            <PatternLayout pattern="${LOG_PATTERN}" />
            <Policies>
                <SizeBasedTriggeringPolicy size="19500KB" />
            </Policies>
            <DefaultRolloverStrategy max="1" />
        </RollingFile>
    </Appenders>

    <Loggers>
        <Logger name="com.howtodoinjava.app" additivity="false">
            <AppenderRef ref="appLog" />
            <AppenderRef ref="Console" />
        </Logger>
        <Root level="debug">
            <AppenderRef ref="Console" />
            <AppenderRef ref="appLog" />
        </Root>
    </Loggers>
</Configuration>

3. Demo

Now add a few log statements in the application and see the logs in configured appenders e.g. I configured console and file.

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.ApplicationContext;
 
@SpringBootApplication
public class Application extends SpringBootServletInitializer {
 
  private static final Logger LOGGER = LogManager.getLogger(Application.class);
 
  public static void main(String[] args)
    {
        ApplicationContext ctx = SpringApplication.run(Application.class, args);
         
        LOGGER.info("Info level log message");
        LOGGER.debug("Debug level log message");
        LOGGER.error("Error level log message");
    }
}

Check the output in the console and the log file.

2018-06-01T13:55:42.506+0530 INFO Info level log message
2018-06-01T13:55:42.506+0530 DEBUG Debug level log message
2018-06-01T13:55:42.506+0530 ERROR Error level log message

Let me know if you face any problems in this spring boot log4j2 example.

Happy Learning !!

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