ClassNotFoundException: zipkin.reporter.Sender

[ssasporta]

While running application including the jar: stagemonitor-tracing-zipkin-0.88.4-SNAPSHOT.jar I receive the following exception:

     ClassNotFoundException: zipkin.reporter.Sender

    at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671) [na:1.8.0_141]
    at java.lang.Class.getConstructor0(Class.java:3075) [na:1.8.0_141]
    at java.lang.Class.newInstance(Class.java:412) [na:1.8.0_141]
    at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:380) [na:1.8.0_141]
    ... 175 common frames omitted Caused by: java.lang.ClassNotFoundException: zipkin.reporter.Sender
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381) ~[na:1.8.0_141]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_141]
    at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:93) ~[spring-petclinic-2.0.0.BUILD-SNAPSHOT.jar:2.0.0.BUILD-SNAPSHOT]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_141]
    ... 180 common frames omitted

I don't understand how to solve it. Where should this class exists?

Thanks
Sharon