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Spring Boot Log4j2 Example | XML + YAML + JSON

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Spring Boot by default uses Logback framework for logging when we use Spring Boot Starter dependency. Apache Log4j 2 is the successor of Log4j which provides significant improvements over its predecessor Log4j 1.x and provides many of the features available in Logback. In this Spring Boot Log4j2 Example, we will learn how to configure the log4j 2 framework in Spring boot application.

Spring boot provides a default starter for logging spring-boot-starter-logging. It is included by default in spring-boot-starter. In order to use Log4j2, we will be excluding spring-boot-starter-logging

Folder Structure:

Spring Boot Log4j2 Example

  • Create a Maven project (maven-archetype-quickstart) “SpringBootLog4j2” and create a package for our source files “com.javainterviewpoint” under  src/main/java 
  • Now add the following dependency in the POM.xml 
    <project xmlns="http://maven.apache.org/POM/4.0.0"	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.javainterviewpoint</groupId>
	<artifactId>SpringBootLog4j2</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>SpringBootLog4j2</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.1.RELEASE</version>
	</parent>
	<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> -->
				<exclusion>
					<groupId>org.springframework.boot</groupId>
					<artifactId>spring-boot-starter-logging</artifactId>
				</exclusion>
				<exclusion>
					<artifactId>logback-classic</artifactId>
					<groupId>ch.qos.logback</groupId>
				</exclusion>
				<exclusion>
					<artifactId>log4j-over-slf4j</artifactId>
					<groupId>org.slf4j</groupId>
				</exclusion>
			</exclusions>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-log4j2</artifactId>
		</dependency>
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.7.4</version>
		</dependency>

		<dependency>
			<groupId>com.fasterxml.jackson.dataformat</groupId>
			<artifactId>jackson-dataformat-yaml</artifactId>
			<version>2.7.4</version>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
</project>
  • Adding the dependency jackson-dataformat-yaml, jackson-databind to read the log4j2.yaml and log4j2.json configuration files
  • Create the Java classes App.java under com.javainterviewpoint folder.
  • Create log4j2.xml / log4j2.json / log4j2.yaml file under src/main/resources directory.

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Spring Boot Log4j2 Example

Dependency Tree

[INFO] ------------------------------------------------------------------------
[INFO] Building SpringBootLog4j2 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-dependency-plugin:2.10:tree (default-cli) @ SpringBootLog4j2 ---
[INFO] com.javainterviewpoint:SpringBootLog4j2:jar:0.0.1-SNAPSHOT
[INFO] +- org.springframework.boot:spring-boot-starter:jar:1.5.1.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot:jar:1.5.1.RELEASE:compile
[INFO] |  |  \- org.springframework:spring-context:jar:4.3.6.RELEASE:compile
[INFO] |  |     +- org.springframework:spring-aop:jar:4.3.6.RELEASE:compile
[INFO] |  |     +- org.springframework:spring-beans:jar:4.3.6.RELEASE:compile
[INFO] |  |     \- org.springframework:spring-expression:jar:4.3.6.RELEASE:compile
[INFO] |  +- org.springframework.boot:spring-boot-autoconfigure:jar:1.5.1.RELEASE:compile
[INFO] |  +- org.springframework:spring-core:jar:4.3.6.RELEASE:compile
[INFO] |  \- org.yaml:snakeyaml:jar:1.17:compile
[INFO] +- org.springframework.boot:spring-boot-starter-log4j2:jar:1.5.1.RELEASE:compile
[INFO] |  +- org.apache.logging.log4j:log4j-slf4j-impl:jar:2.7:compile
[INFO] |  |  \- org.slf4j:slf4j-api:jar:1.7.22:compile
[INFO] |  +- org.apache.logging.log4j:log4j-api:jar:2.7:compile
[INFO] |  +- org.apache.logging.log4j:log4j-core:jar:2.7:compile
[INFO] |  +- org.slf4j:jcl-over-slf4j:jar:1.7.22:compile
[INFO] |  \- org.slf4j:jul-to-slf4j:jar:1.7.22:compile
[INFO] +- com.fasterxml.jackson.core:jackson-databind:jar:2.7.4:compile
[INFO] |  +- com.fasterxml.jackson.core:jackson-annotations:jar:2.8.0:compile
[INFO] |  \- com.fasterxml.jackson.core:jackson-core:jar:2.8.6:compile
[INFO] \- com.fasterxml.jackson.dataformat:jackson-dataformat-yaml:jar:2.7.4:compile

Spring boot Log4j2 Configuration

Spring Boot automatically configures Log4j2 the moment it finds a file named log4j2.xml or log4j2.json or log4j2.yaml in the classpath.

log4j2.xml

Create log4j2.xml file under src/main/resources folder

<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
	 <Appenders>
		<Console name="ConsoleAppender" target="SYSTEM_OUT">
			<PatternLayout pattern="%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n" />
		</Console>
		
		<File name="FileAppender" fileName="D:/JIP/Application.log">
			<PatternLayout pattern="%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n" />
		</File>
	</Appenders>
	
	<Loggers>
		<!-- Logging custom package -->
		<Logger name="com.javainterviewpoint" level="debug" additivity="false">
			<AppenderRef ref="ConsoleAppender"></AppenderRef>
			<AppenderRef ref="FileAppender"></AppenderRef>
		</Logger>
		<!-- Logging spring boot package -->
		<Logger name="org.springframework.boot" level="debug" additivity="false">
      		<AppenderRef ref="ConsoleAppender"></AppenderRef>
			<AppenderRef ref="FileAppender"></AppenderRef>
   		</Logger>
		<Root level="warn">
      		<AppenderRef ref="ConsoleAppender"></AppenderRef>
			<AppenderRef ref="FileAppender"></AppenderRef>
    	</Root>
	</Loggers>
</Configuration>

log4j2.yaml

Spring Boot requires  “jackson-dataformat-yaml” dependency to pick up the yaml file.

Configutation:
  name: Default

  Appenders:

    Console:
      name: ConsoleAppender
      target: SYSTEM_OUT
      PatternLayout:
        pattern: "%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n"

    File:
      name: FileAppender
      fileName: D:/JIP/Application.log
      PatternLayout:
        pattern: "%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n"

  Loggers:

      Root:
        level: debug
        AppenderRef:
          - ref: ConsoleAppender

      Logger:
        - name: com.javainterviewpoint
          level: debug
          AppenderRef:
            - ref: FileAppender
              level: debug

log4j2.json

Add “jackson-databind” dependency so that spring boot reads the json configuration

{
  "configuration": {
    "name": "Default",
    "appenders": {
      "Console": {
        "name": "ConsoleAppender",
        "target": "SYSTEM_OUT",
        "PatternLayout": {
          "pattern": "%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n"
        }
      },
      "File": {
        "name": "FileAppender",
        "fileName": "D:/JIP/Application.log",
        "PatternLayout": {
          "pattern": "%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n"
        }
      }
    },
    "loggers": {
      "logger": {
        "name": "com.javainterviewpoint",
        "level": "debug",
        "appender-ref": [{"ref": "ConsoleAppender", "level":"debug"},{"ref": "FileAppender", "level":"debug"}]
      },
	  "logger": {
        "name": "org.springframework.boot",
        "level": "debug",
        "appender-ref": [{"ref": "ConsoleAppender", "level":"debug"},{"ref": "FileAppender", "level":"debug"}]
      },
      "root": {
        "level": "debug",
        "appender-ref": {"ref": "ConsoleAppender"}
      }
    }
  }
}

Log4j2 properties (log4j2.properties)

You can still add have the tradition Log4j2 properties file for configuring Log4j 2

name=PropertiesConfig
appenders = console, file

appender.console.type = Console
appender.console.name = ConsoleAppender
appender.console.layout.type = PatternLayout
appender.console.layout.pattern = %d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n

appender.file.type = File
appender.file.name = FileAppender
appender.file.fileName=D:/JIP/Application_properties.log
appender.file.layout.type=PatternLayout
appender.file.layout.pattern= %d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n

loggers=file
logger.file.name=com.javainterviewpoint
logger.file.level = debug
logger.file.appenderRefs = file
logger.file.appenderRef.file.ref = FileAppender

rootLogger.level = debug
rootLogger.appenderRefs = stdout
rootLogger.appenderRef.stdout.ref = ConsoleAppender

App.java

package com.javainterviewpoint;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class App implements ApplicationRunner
{
    private static Logger logger = LogManager.getLogger(App.class);

    public static void main(String[] args) 
    {
        SpringApplication.run(App.class, args);
    }
    @Override
    public void run(ApplicationArguments applicationArguments) throws Exception
    {
        logger.debug("Debugging log");
        logger.info("Info log");
        logger.warn("Warning log");
        logger.error("Error log");
        logger.fatal("Fatal log");
    }
}

The App class main() method is the triggering point of our application, it in-turn calls Spring Boot’s SpringApplication class run() method which bootstrap our App application. We need to pass our App.class as an argument to our run() method. We have printed some logging statements.

Output:

Run the spring boot application using “mvn spring-boot:run”

 .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.5.1.RELEASE)

01:25 21:53:43.364 [main] [INFO] [com.javainterviewpoint.App] - Starting App on Jack-PC with PID 4228 (D:\sts-3.8.3.RELEASE\Workspace\SpringBootLog4j2\target\classes started by Jack in D:\sts-3.8.3.RELEASE\Workspace\SpringBootLog4j2)
01:25 21:53:43.365 [main] [DEBUG] [com.javainterviewpoint.App] - Running with Spring Boot v1.5.1.RELEASE, Spring v4.3.6.RELEASE
01:25 21:53:43.365 [main] [INFO] [com.javainterviewpoint.App] - No active profile set, falling back to default profiles: default
01:25 21:53:43.365 [main] [DEBUG] [org.springframework.boot.SpringApplication] - Loading source class com.javainterviewpoint.App
01:25 21:53:44.094 [main] [DEBUG] [org.springframework.boot.admin.SpringApplicationAdminMXBeanRegistrar$SpringApplicationAdmin] - Application Admin MBean registered with name 'org.springframework.boot:type=Admin,name=SpringApplication'
01:25 21:53:44.158 [main] [DEBUG] [org.springframework.boot.autoconfigure.logging.AutoConfigurationReportLoggingInitializer] - 


=========================
AUTO-CONFIGURATION REPORT
=========================


Positive matches:
-----------------

   GenericCacheConfiguration matched:
      - Cache org.springframework.boot.autoconfigure.cache.GenericCacheConfiguration automatic cache type (CacheCondition)

   JmxAutoConfiguration matched:
      - @ConditionalOnClass found required class 'org.springframework.jmx.export.MBeanExporter'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
      - @ConditionalOnProperty (spring.jmx.enabled=true) matched (OnPropertyCondition)

   JmxAutoConfiguration#mbeanExporter matched:
      - @ConditionalOnMissingBean (types: org.springframework.jmx.export.MBeanExporter; SearchStrategy: current) did not find any beans (OnBeanCondition)

   JmxAutoConfiguration#mbeanServer matched:
      - @ConditionalOnMissingBean (types: javax.management.MBeanServer; SearchStrategy: all) did not find any beans (OnBeanCondition)

   JmxAutoConfiguration#objectNamingStrategy matched:
      - @ConditionalOnMissingBean (types: org.springframework.jmx.export.naming.ObjectNamingStrategy; SearchStrategy: current) did not find any beans (OnBeanCondition)

Negative matches:
-----------------

   ActiveMQAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory', 'org.apache.activemq.ActiveMQConnectionFactory' (OnClassCondition)

   AopAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'org.aspectj.lang.annotation.Aspect', 'org.aspectj.lang.reflect.Advice' (OnClassCondition)

   ArtemisAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory', 'org.apache.activemq.artemis.jms.client.ActiveMQConnectionFactory' (OnClassCondition)

   BatchAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'org.springframework.batch.core.launch.JobLauncher', 'org.springframework.jdbc.core.JdbcOperations' (OnClassCondition)

   CacheAutoConfiguration:
      Did not match:
         - @ConditionalOnBean (types: org.springframework.cache.interceptor.CacheAspectSupport; SearchStrategy: all) did not find any beans (OnBeanCondition)
      Matched:
         - @ConditionalOnClass found required class 'org.springframework.cache.CacheManager'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)

Exclusions:
-----------

    None

Unconditional classes:
----------------------
    org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration

    org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration

    org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration

    org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration


01:25 21:53:44.174 [main] [DEBUG] [com.javainterviewpoint.App] - Debugging log
01:25 21:53:44.175 [main]  [INFO] [com.javainterviewpoint.App] - Info log
01:25 21:53:44.175 [main] [WARN] [com.javainterviewpoint.App] - Warning log
01:25 21:53:44.176 [main] [ERROR] [com.javainterviewpoint.App] - Error log
01:25 21:53:44.176 [main] [FATAL] [com.javainterviewpoint.App] - Fatal log
01:25 21:53:44.177 [main] [INFO] [com.javainterviewpoint.App] - Started App in 1.244 seconds (JVM running for 2.269)

Spring Boot Rolling File Appender

If you want a new log file to be created whenever the file reaches a certain threshold size, then you can go for RollingFile Appender, in order to add a RollingFile add the below code in the log4j2.xml

<RollingFile name="FileAppender" fileName="D:/JIP/Application_Roll.log"
	filePattern="D:/JIP/Application_Roll-%d{yyyy-MM-dd}-%i.log">
	<PatternLayout>
		<Pattern>%d{MM:dd HH:mm:ss.SSS} [%t] [%level] [%logger{36}] - %msg%n</Pattern>
	</PatternLayout>
		<Policies>
			<SizeBasedTriggeringPolicy size="1 MB" />
		</Policies>
		<DefaultRolloverStrategy max="5" />
</RollingFile>

As per the above configuration, a new file will be created whenever the log file size reaches 1 MB since we have set up the SizeBasedTriggeringPolicy to 1 MB, The <DefaultRollOverStrategy max=”5″ /> element defines the maximum number of log files which will be kept.

Happy Learning 🙂

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