How to integrate SLF4J logging with Spring 4? - maven

Question

Couldn't find any good answer why slf4j logging not working with spring 4. Thanks to this post I've made particularly all work, but the author didn't mention that:
The mandatory logging dependency in Spring is the Jakarta Commons Logging API (JCL)
(http://docs.spring.io/spring/docs/4.1.x/spring-framework-reference/htmlsingle/).
It means that if we want slf4j to work WE MUST EXCLUDE commons-logging from our classpath (or pom.xml if using maven). While using maven spring-core automatically picks commons-logging. (I understood this when executed the command "mvn dependency:tree").
STEPS TO REPRODUCE:
Exclude commons-logging from spring-core
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
<exclusions>
<exclusion>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
Add to the pom.xml next dependencies:
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.19</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
<version>1.7.19</version>
</dependency>
Create log4j2.xml file like this (if you want log4j2 logging through slf4j).
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
<Appenders>
<Console name="CONSOLE" target="SYSTEM_OUT">
<PatternLayout
pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
</Console>
</Appenders>
<Loggers>
<Root level="error">
<AppenderRef ref="CONSOLE" />
</Root>
<logger level="info" additivity="false" name="org.springframework.security">
<AppenderRef ref="CONSOLE" />
</logger>
<logger level="info" additivity="false" name="org.springframework.web">
<AppenderRef ref="CONSOLE" />
</logger>
<logger level="warn" additivity="false" name="controllers">
<AppenderRef ref="CONSOLE" />
</logger>
</Loggers>
</Configuration>
write log messages in your classes:
private final Logger logger =LoggerFactory.getLogger(this.getClass());
logger.debug("This is a debug message");
logger.info("This is an info message");

Answer 1

You do not need to exclude commons-logging. If you use log4j-jcl instead of jcl-over-slf4j the Spring logging will be routed to log4j directly instead of going through slf4j.

Answer 2

Now, thanx to #rgoers my logging part of pom.xml looks like:
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.19</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-jcl</artifactId>
<version>2.5</version>
</dependency>