Multiple SLF4J bindings cause error?

问题:

I have a problem with my dependency tree and multiple SLF4J binding. What I found out so far is that usually this only causes a warning but in my case it seems to prevent my program from running: These are the exceptions I get:

SLF4J: Class path contains multiple SLF4J bindings. SLF4J: Found binding in [jar:file:/C:/Users/FischerNi/.m2/repository/org/slf4j/slf4j-jdk14/1.5.3/slf4j-jdk14-1.5.3.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: Found binding in [jar:file:/C:/Users/FischerNi/.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. SLF4J: slf4j-api 1.6.x (or later) is incompatible with this binding. SLF4J: Your binding is version 1.5.5 or earlier. SLF4J: Upgrade your binding to version 1.6.x. or 2.0.x Exception in thread "main" java.lang.NoSuchMethodError: org.slf4j.impl.StaticLoggerBinder.getSingleton()Lorg/slf4j/impl/StaticLoggerBinder;

and this is the relevant piece of my dependencies: net.lightbody.bmp browsermob-proxy 2.0-beta-8

    <!-- LOGGING DEPENDENCIES - LOG4J -->
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
    </dependency>

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
    </dependency>

Can somebody please tell me how to resolve this issue?

回答1:

There are couple of solutions to this:

• Make sure that you include only one slf4j jar(probably with the higher version) if you have couple of them with different versions on your class path.
• Sometimes it may not be possible to exclude multiple slf4j jars, as they may be used by other jars internally, which are on your class path. These dependent jar may refer to different versions of slf4j jars which causes your application to fail. In such cases, make sure that you have the jar with higher version of SLF4j added before other jar using SLF4J jars. This will make sure that your java program will pick up the latest version of the SLF4J which obviously is backward compatible.

回答2:

If your project has dependency on other project and the other one use slf4j as well with different version try to use excusion

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

回答3:

Answer from Fateh is correct I had to spend some time to figure out how to use it, that's why I'm adding a complete solution:

1. Run mvn dependency:tree

2. find out which library is using slf4j:

   [INFO] +- net.lightbody.bmp:browsermob-proxy:jar:2.0-beta-8:compile
   [INFO] |  +- org.slf4j:slf4j-jdk14:jar:1.7.25:compile
   

3. exclude it from maven like this:

        <dependency>
           <groupId>net.lightbody.bmp</groupId>
           <artifactId>browsermob-proxy</artifactId>
           <version>2.0.0</version>
           <exclusions>
               <exclusion>
                   <groupId>org.slf4j</groupId>
                   <artifactId>slf4j-jdk14</artifactId>
               </exclusion>
           </exclusions>
       </dependency>
   

回答4:

I would suggest to use following dependency in maven instead,

<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>

This has solved my problem although I have more dependencies using slf4j.

回答5:

This is occur when there is more than one jar. To check if there jar is already available or not go to project -> java resources -> maven dependencies and check if the jar is already available there or not . If its available and still you get the error . Then find the location of that jar file in .m2\resources folder and delete complete folder related to that jar file then download a newer version and import it to your project . :)

Sometime i get errors even i have download the right jar file with a right version in my pom.xml file. Then i need to remove it from my pom.xml and download that jar from google and import it to my project.Make sure if you do it then don't forget to go Project properties ->Deployment Assembly tab->Click Add ->Java Build Path Entries and Click on that jar file and Click apply .

回答6:

When multiple bindings are available on the class path, select one and only one binding you wish to use, and remove the other bindings.

Try removing explicitly added dependency of 'org.slf4j' or 'log4j2'.