SLF4J: Class path contains multiple SLF4J bindings

Question

I'm getting the following error. It seems there are multiple logging frameworks bound to slf4j. 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.

Solution 1

Resolved by adding the following exclusion in the dependencies (of pom.xml) that caused conflict.

<exclusions>
    <exclusion>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
    </exclusion>
</exclusions> 

Solution 2

Gradle version;

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

Solution 3

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 not to 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)

Solution 4

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")
)

Solution 5

1.Finding the conflicting jar

If it's not possible to identify the dependency from the warning, then you can use the following command to identify the conflicting jar

mvn dependency: tree

This will display the dependency tree for the project and dependencies who have pulled in another binding with the slf4j-log4j12 JAR.

2. Resolution

Now that we know the offending dependency, all that we need to do is exclude the slf4j-log4j12 JAR from that dependency.

Ex - if spring-security dependency has also pulled in another binding with the slf4j-log4j12 JAR, Then we need to exclude the slf4j-log4j12 JAR from the spring-security dependency.

 <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
           <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
    </dependency>

Note - In some cases multiple dependencies have pulled in binding with the slf4j-log4j12 JAR and you don't need to add exclude for each and every dependency that has pulled in. You just have to do that add exclude dependency with the dependency which has been placed at first.

Ex -

<dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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-security</artifactId>
        </dependency>

</dependencies>

If you work with gradle then add following code to your build.gradle file to exclude SLF4J binding from all the modules

configurations.all {
    exclude group: 'org.springframework.boot', module: 'spring-boot-starter-logging'
}

View more solutions

Comments

[user1493140]

Resolved Using <exclusions> <exclusion> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> </exclusion> </exclusions> in the dependecies (of pom.xml) that caused conflict helped resolve the problem

[michael]

duplicate: stackoverflow.com/questions/8921382/…

[Peter Keller]

Did you already check slf4j.org/codes.html#multiple_bindings as stated in the warning?

[Roberto]

Maybe It could be better to add an answer (auto-answer) to this question and mark it as "Accepted", So the question will appear as "Solved" in the SO searchs

[user1493140]

Roberto, Thanks for feedback. I copied the solution from the comment and posted it as answer.

[Amit Sinha]

I am getting the same error but in Pom.xml file we don't have slf4j dependency.

[granadaCoder]

For future readers, here is a good article for log4j2 (<<emphasis on the "2" here) logicbig.com/tutorials/spring-framework/spring-boot/log4j2.h‌​tml the key phrase in the article is : "spring-boot-starter-log4j2 is a starter for using Log4j2. It is an alternative to spring-boot-starter-logging."

[Master Mind]

Add exclude dependency with the dependency which has been placed at first.

[PUG]

which dependancy caused conflict in this case, I have dependancy tree there are 3 mentions of slf4j

[Will]

Importing Models from the main application into automation framework.. this resolved my problem with gradle. ty.

[Balaji Boggaram Ramanarayan]

Is there any ant version of doing this ?

[cyber-monk]

to find out how log4j is getting on your path run mvn dependency:tree and comb through, then add the snippet above to that dependency in your pom.xml

[Matthew Mark Miller]

no: ant is not a dependency aware tool. Strongly consider porting your build to gradle.

[ioleo]

strongly recomend porting your build to sbt :)

[Ashok kumar Ganesan]

@user1493140 Still it is not working for me. <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> <exclusions> <exclusion> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> </exclusion> </exclusions> </dependency>

[Petrus Theron]

What does Sbt stand for?

[PlunkettBoy]

Excellent. Saved me from a few hours of dependency hell!

[Benny]

Simple Build Tool*

[Jan Lochman]

Thank you for introducing mvn dependency:tree. It's so much helpful...

[ihebiheb]

for me another jar war the cause. I had to exclude the artifacts with id slf4j-nop and slf4j-jdk14. The dependency that caused the conflict for me was clover-maven-plugin

[Lei Yang]

not clear: do you mean delete/comment above xml section, or add?

[Lei Yang]

is the version (slf4j-log4j12) applicable for all? or should we find out the version from mvn dependency:tree?

[Jhon Hernández]

After number 1, the other options doesn´t appera anymore...thanks more things to fix

[Partha Paul]

How to do in Maven?

[Kerem]

@ParthaPaul the previous answer is the one for that. stackoverflow.com/a/22638585/1505341