Unable to find an implementation for interface io.jsonwebtoken.io.Serializer ... in fat jar

Hi guys,

We are seeing this error: Unable to find an implementation for interface io.jsonwebtoken.io.Serializer using java.util.ServiceLoader. Ensure you include a backing implementation .jar in the classpath, for example, jjwt-impl.jar, or your own .jar for custom implementations.

Of course, we’ve included all deps:

     implementation 'io.jsonwebtoken:jjwt-api:0.11.0'
     implementation 'io.jsonwebtoken:jjwt-impl:0.11.0'
     implementation 'io.jsonwebtoken:jjwt-gson:0.11.0'

We are using a fat jar (all jars merged into one big jar). I’ve checked and the classes are present in our fat jar:

$ jar tf releases/server-1.20.42.jar | grep jsonwebtoken.*Serializer
io/jsonwebtoken/io/JacksonSerializer.class
io/jsonwebtoken/gson/io/GsonSerializer.class
io/jsonwebtoken/io/Serializer.class

There’s something I’m missing because this class is loaded using the standard ServiceLoader which says:

A service provider is identified by placing a provider-configuration file in the resource directory META-INF/services. The file’s name is the fully-qualified binary name of the service’s type.

Well, I can see any such file in the jjwt-gson:

$ mkdir temp; cd temp
$ jar xf ~/.gradle/caches/modules-2/files-2.1/io.jsonwebtoken/jjwt-gson/0.11.0/8042478d4d0024aa4edb0d608475093acfc7f3e8/jjwt-gson-0.11.0.jar
$ find -type f
./io/jsonwebtoken/gson/io/GsonSerializer.class
./io/jsonwebtoken/gson/io/GsonDeserializer.class
./META-INF/MANIFEST.MF
./META-INF/maven/io.jsonwebtoken/jjwt-gson/pom.xml
./META-INF/maven/io.jsonwebtoken/jjwt-gson/pom.properties

So I’m not sure how this is supposed to work.

[masterdany88]

Hi. I have same issue while working with war package. I have jjwt-impl-0.11.1.jar and jjwt-api-0.11.1.jar inside App-server-0.0.2-SNAPSHOT.war\WEB-INF\lib
But tomcat prints error: 04-Jun-2020 19:55:53.156 SEVERE [http-nio-9000-exec-2] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [com.qiagen.qbase.qbap.server.conf.RestConfig] in context with path [] threw exception [io.jsonwebtoken.lang.UnknownClassException: Unable to find an implementation for interface io.jsonwebtoken.io.Serializer using java.util.ServiceLoader. Ensure you include a backing implementation .jar in the classpath, for example jjwt-impl.jar, or your own .jar for custom implementations.] with root cause io.jsonwebtoken.impl.lang.UnavailableImplementationException: Unable to find an implementation for interface io.jsonwebtoken.io.Serializer using java.util.ServiceLoader. Ensure you include a backing implementation .jar in the classpath, for example jjwt-impl.jar, or your own .jar for custom implementations. at io.jsonwebtoken.impl.lang.Services.loadFirst(Services.java:105) at io.jsonwebtoken.impl.lang.LegacyServices.loadFirst(LegacyServices.java:21) at io.jsonwebtoken.impl.DefaultJwtBuilder.compact(DefaultJwtBuilder.java:300) at com.app.adapter.jwt.JwtAdapter.create(JwtAdapter.java:43)

UPDATE

Oh. Ive added:

<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt-jackson</artifactId> <!-- or jjwt-gson if Gson is preferred -->
    <version>0.11.1</version>
    <scope>runtime</scope>
</dependency>

and now it works.

[darioseidl]

Is a serializer JAR (for Jackson or Gson) required?

Like @mbogner said,

With 0.11.2 I got the same error that impl couldn’t be found. Adding the jackson lib as stated above solved that problem for me as well.

with 0.11.2 I’m also seeing this error unless I include the Jackson or Gson jar and the error message is misleading as it says that the jjwt-impl.jar is missing, but it’s actually the jjwt-jackson.jar that was missing in my case:

    implementation("io.jsonwebtoken:jjwt-api:0.11.2")
    runtimeOnly("io.jsonwebtoken:jjwt-impl:0.11.2")

results in:

Unable to find an implementation for interface io.jsonwebtoken.io.Serializer using java.util.ServiceLoader. Ensure you include a backing implementation .jar in the classpath, for example, jjwt-impl.jar, or your own .jar for custom implementations

but this works:

    implementation("io.jsonwebtoken:jjwt-api:0.11.2")
    runtimeOnly("io.jsonwebtoken:jjwt-impl:0.11.2")
    runtimeOnly("io.jsonwebtoken:jjwt-jackson:0.11.2")