SLF4J: Class path contains multiple SLF4J bindings

Question

I'm getting the following error. It seems there are multiple logging frameworks bound to sl4j. Not sure how to resolve this. Any help is greatly appreciated.

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/C:/Users/admin/.m2/repository/org/slf4j/slf4j-log4j12/1.6.4/slf4j-log4j12-1.6.4.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/C:/Users/admin/.m2/repository/org/slf4j/slf4j-log4j12/1.6.1/slf4j-log4j12-1.6.1.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.

Answer 1

The error probably gives more information like this (although your jar names could be different)

SLF4J: Found binding in [jar:file:/D:/Java/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: Found binding in [jar:file:/D:/Java/repository/org/apache/logging/log4j/log4j-slf4j-impl/2.8.2/log4j-slf4j-impl-2.8.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]

Noticed that the conflict comes from two jars, named logback-classic-1.2.3 and log4j-slf4j-impl-2.8.2.jar.

Run mvn dependency:tree in this project pom.xml parent folder, giving:

Now choose the one you want to ignore (could consume a delicate endeavor I need more help on this)

I decided to not use the one imported from spring-boot-starter-data-jpa (the top dependency) through spring-boot-starter and through spring-boot-starter-logging, pom becomes:

    <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-data-jpa</artifactId>
    </dependency>

in above pom spring-boot-starter-data-jpa would use the spring-boot-starter configured in the same file, which excludes logging (it contains logback)

Answer 2

Sbt version:

Append exclude("org.slf4j", "slf4j-log4j12") to the dependency that transitively includes slf4j-log4j12. For example, when using Spark with Log4j 2.6:

libraryDependencies ++= Seq(
  // One SLF4J implementation (log4j-slf4j-impl) is here:
  "org.apache.logging.log4j" % "log4j-api" % "2.6.1",
  "org.apache.logging.log4j" % "log4j-core" % "2.6.1",
  "org.apache.logging.log4j" % "log4j-slf4j-impl" % "2.6.1",
  // The other implementation (slf4j-log4j12) would be transitively
  // included by Spark. Prevent that with exclude().
  "org.apache.spark" %% "spark-core" % "1.5.1" exclude("org.slf4j", "slf4j-log4j12")
)

Answer 3

Gradle version;

configurations.all {
    exclude module: 'slf4j-log4j12'
}

Answer 4

... org.codehaus.mojo cobertura-maven-plugin 2.7 test ch.qos.logback logback-classic tools com.sun ...

## I fixed with this

... org.codehaus.mojo cobertura-maven-plugin 2.7 test ch.qos.logback logback-classic tools com.sun ...

Answer 5

Seems removing .m2 directory and :

mvn install -DskipTests -T 4 resolved this issue for me.

Answer 6

For me, it turned out to be an Eclipse/Maven issue after switch from log4j to logback. Take a look into your .classpath file and search for the string "log4j".

In my case I had the following there: <classpathentry kind="var" path="M2_REPO/org/slf4j/slf4j-log4j12/1.7.1/slf4j-log4j12-1.7.1.jar"/> <classpathentry kind="var" path="M2_REPO/log4j/log4j/1.2.17/log4j-1.2.17.jar" />

Removing those entries from the file (or you could regenerate it) fixed the issue.