How to integrate SLF4J logging with Spring 4?

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");

rgoers rgoers · Accepted Answer · 2016-06-21T07:24:14

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.

How to integrate SLF4J logging with Spring 4?

2 Answers