Error while integrating slf4j over log4j

Question

I am integrating sl4j over log4j for logging in my spring application, but while starting my tomcat , I am getting an error as :

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/E:/apache-tomcat-8/apache-tomcat-8.0.3/webapp
s/ROOT/WEB-INF/lib/slf4j-jdk14-1.5.6.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/E:/apache-tomcat-8/apache-tomcat-8.0.3/webapps/ROOT/WEB-INF/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/E:/apache-tomcat-8/apache-tomcat-8.0.3/webapps/ROOT/WEB-INF/lib/slf4j-nop-1.5.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.slf4j.impl.JDK14LoggerFactory]
SLF4J: The requested version 1.5.6 by your slf4j binding is not compatible with[1.6, 1.7]
SLF4J: See http://www.slf4j.org/codes.html#version_mismatch for further details.

Dependencies in my pom.xml is:

<dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.7</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-all</artifactId>
            <version>1.9.5</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.1</version>
        </dependency>

        <dependency>
            <groupId>net.sf.ehcache</groupId>
            <artifactId>ehcache-core</artifactId>
            <version>2.5.2</version>
        </dependency>

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.3.2</version>
        </dependency>
        <dependency>
            <groupId>commons-httpclient</groupId>
            <artifactId>commons-httpclient</artifactId>
            <version>3.1</version>
        </dependency>
        <dependency>
            <groupId>joda-time</groupId>
            <artifactId>joda-time</artifactId>
            <version>2.1</version>
        </dependency>
        <dependency>
            <groupId>cglib</groupId>
            <artifactId>cglib</artifactId>
            <version>2.2.2</version>
        </dependency>

        <dependency>
            <groupId>com.sun.xml.bind</groupId>
            <artifactId>jaxb-impl</artifactId>
            <version>2.2.7</version>
        </dependency>
        <dependency>
            <groupId>org.jvnet.jaxb2_commons</groupId>
            <artifactId>jaxb2-basics-runtime</artifactId>
            <version>0.6.0</version>
        </dependency>
        <dependency>
            <groupId>net.sf.opencsv</groupId>
            <artifactId>opencsv</artifactId>
            <version>2.3</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>3.9</version>
        </dependency>
        <dependency>
            <groupId>org.apache.axis</groupId>
            <artifactId>axis</artifactId>
            <version>1.4</version>
        </dependency>
        <dependency>
            <groupId>javax.xml</groupId>
            <artifactId>jaxrpc</artifactId>
            <version>1.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.axis2</groupId>
            <artifactId>axis2</artifactId>
            <version>1.6.2</version>
        </dependency>
        <dependency>
            <groupId>commons-discovery</groupId>
            <artifactId>commons-discovery</artifactId>
            <version>0.2</version>
        </dependency>

        <dependency>
            <groupId>net.sf.json-lib</groupId>
            <artifactId>json-lib</artifactId>
            <version>2.4</version>
            <classifier>jdk15</classifier>
        </dependency>
        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
            <version>1.0.0.GA</version>
        </dependency>
        <dependency>
            <groupId>javax.annotation</groupId>
            <artifactId>jsr250-api</artifactId>
            <version>1.0</version>
        </dependency>

        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.2.2</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpmime</artifactId>
            <version>4.2.5</version>
        </dependency>

        <dependency>
            <groupId>javax.mail</groupId>
            <artifactId>mail</artifactId>
            <version>1.4</version>
        </dependency>
        <dependency>
            <groupId>org.quartz-scheduler</groupId>
            <artifactId>quartz</artifactId>
            <version>1.8.6</version>
        </dependency>

        <dependency>
            <groupId>commons-net</groupId>
            <artifactId>commons-net</artifactId>
            <version>3.3</version>
        </dependency>
        <dependency>
            <groupId>com.servletsuite</groupId>
            <artifactId>random</artifactId>
            <version>1.7</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.tiles</groupId>
            <artifactId>tiles-extras</artifactId>
            <version>${tiles-version}</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.1</version>
        </dependency>

        <!-- Spring starts here -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-oxm</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>


        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${org.springframework.version}</version>
            <exclusions>
                <exclusion>
                    <groupId>commons-logging</groupId>
                    <artifactId>commons-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <!--Spring Security -->
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-core</artifactId>
            <version>${org.springsecurity-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-config</artifactId>
            <version>${org.springsecurity-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-taglibs</artifactId>
            <!-- <version>3.2.0.RELEASE</version> -->
            <version>${org.springsecurity-version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-web</artifactId>
            <version>${org.springsecurity-version}</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.0-api</artifactId>
            <version>1.0.1.Final</version>
        </dependency>

        <dependency>
            <groupId>net.sf.ehcache</groupId>
            <artifactId>ehcache</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>commons-collections</groupId>
            <artifactId>commons-collections</artifactId>
            <version>3.2.1</version>
        </dependency>
        <dependency>
            <groupId>commons-validator</groupId>
            <artifactId>commons-validator</artifactId>
            <version>1.4.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>2.5</version>
        </dependency>

        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>3.9</version>
        </dependency>


        <!-- AspectJ -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>${org.aspectj-version}</version>
        </dependency> 

        <!-- Logging -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${org.slf4j-version}</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${org.slf4j-version}</version>
            <scope>runtime</scope>
            <exclusions>
                <exclusion>
                    <groupId>log4j</groupId>
                    <artifactId>log4j</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-1.2-api</artifactId>
            <version>2.0.2</version>
        </dependency>

        <!-- @Inject -->
        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

        <!--  Hibernate  -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>4.2.0.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate.common</groupId>
            <artifactId>hibernate-commons-annotations</artifactId>
            <version>4.0.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${hibernate.version}</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate.javax.persistence</groupId>
            <artifactId>hibernate-jpa-2.0-api</artifactId>
            <version>1.0.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${hibernate.version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-ehcache</artifactId>
            <version>${hibernate.version}</version>
        </dependency>

        <!-- Spring Social -->
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-config</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-core</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-security</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-web</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>

        <!-- Spring Social Facebook -->
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-facebook</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>

        <!-- Spring Social Twitter -->
        <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-twitter</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency>

        <!-- Spring Social google -->
        <!-- <dependency>
            <groupId>org.springframework.social</groupId>
            <artifactId>spring-social-google</artifactId>
            <version>${org.springframework.social.version}</version>
        </dependency> -->

        <!-- Spring Data JPA -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jpa</artifactId>
            <version>2.0.8</version>
        </dependency>

    </dependencies>

It is clear that there are some mismatch of class file version as some other dependency may using log4j of some other version which I need to exclude in my pom, but unable to figure the appropriate one, please help.

Answer 1

Your pom includes this dependency:

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-1.2-api</artifactId><!-- bridge between log4j-1.2 and log4j2-->
        <version>2.0.2</version>
    </dependency>

This is a bridge jar to use log4j2 in an application whose code uses the log4j-1.2 API. The bridge jar alone is not sufficient: if you want to use log4j2, you need to add also the log4j-api and the log4j-core dependencies. (See the log4j2 FAQ on which jars to use.)

Furthermore, if you (or any of the libraries you use) use slf4j, then also add the log4j-slf4j-impl dependency. Similarly, commons-logging is supported in the log4j-jcl dependency.

So, add the dependencies below:

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.0.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId><!-- log4j2 implementation-->
        <version>2.0.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-jcl</artifactId><!-- bridge to commons-logging-->
        <version>2.0.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j-impl</artifactId><!-- bridge to slf4j-->
        <version>2.0.2</version>
    </dependency>

By the way, the latest version of log4j2 is 2.2, so instead of 2.0.2 you may want to use 2.2.

Also, remove this dependency (it forwards to the log4j-1.2 implementation):

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>${org.slf4j-version}</version>
        <scope>runtime</scope>
        <exclusions>
            <exclusion>
                <groupId>log4j</groupId>
                <artifactId>log4j</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

Answer 2

Slf4j is telling you multiple issues:

• You are using multiple versions, which might be incompatible to each other.
• There are multiple implementations of StaticLoggerBinder available.

Probably your dependencies include other slf4j dependencies, to find them you can use mvn dependency:tree and exclude them in your pom.xml.

Also, you should choose which underlying logger you want to use in your application. http://www.slf4j.org/images/concrete-bindings.png

Right now, slf4j uses the JDK14LoggerFactory, which i think could be a good decision if you run your app inside tomcat.

What you should finally do?

Remove slf4j-log4j12.jar and slf4j-nop-1.5.3.jar from your classpath (WEB-INF/lib) by excluding the implicit imports in your pom.xml, but add slf4j-jdk14.jar explicit. Also, i would consider to remove all the log4j-jars and replace them with the log4j-over-slf4j.jar.

log4j-over-slf4j.jar is using slf4j's backend, but implements the log4j interfaces and is fully API compatible.