MongoDB Reactive Streams run-time dependency error with Alpakka Mongo Connector ClassNotFoundException

问题

I'm trying to integrate the Alpakka Mongo Connector into an application that heavily relies on the Akka libraries for stream processing. The application utilizes Akka HTTP as well.
I am encountering a dependency issue at run-time. In particular, I'm getting a NoClassDefFoundError for some kind of Success/Failure wrappers when I try to use the MongoSink.insertOne method provided by the Mongo connector. A full stack-trace:

java.lang.NoClassDefFoundError: com/mongodb/reactivestreams/client/Success
    at akka.stream.alpakka.mongodb.scaladsl.MongoFlow$.$anonfun$insertOne$1(MongoFlow.scala:44)
    at akka.stream.impl.fusing.Map$$anon$1.onPush(Ops.scala:53)
    at akka.stream.impl.fusing.GraphInterpreter.processPush(GraphInterpreter.scala:541)
    at akka.stream.impl.fusing.GraphInterpreter.execute(GraphInterpreter.scala:423)
    at akka.stream.impl.fusing.GraphInterpreterShell.runBatch(ActorGraphInterpreter.scala:625)
    at akka.stream.impl.fusing.ActorGraphInterpreter$SimpleBoundaryEvent.execute(ActorGraphInterpreter.scala:56)
    at akka.stream.impl.fusing.ActorGraphInterpreter$SimpleBoundaryEvent.execute$(ActorGraphInterpreter.scala:52)
    at akka.stream.impl.fusing.ActorGraphInterpreter$BatchingActorInputBoundary$OnNext.execute(ActorGraphInterpreter.scala:95)
    at akka.stream.impl.fusing.GraphInterpreterShell.processEvent(ActorGraphInterpreter.scala:600)
    at akka.stream.impl.fusing.ActorGraphInterpreter.akka$stream$impl$fusing$ActorGraphInterpreter$$processEvent(ActorGraphInterpreter.scala:769)
    at akka.stream.impl.fusing.ActorGraphInterpreter$$anonfun$receive$1.applyOrElse(ActorGraphInterpreter.scala:784)
    at akka.actor.Actor.aroundReceive(Actor.scala:537)
    at akka.actor.Actor.aroundReceive$(Actor.scala:535)
    at akka.stream.impl.fusing.ActorGraphInterpreter.aroundReceive(ActorGraphInterpreter.scala:691)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:577)
    at akka.actor.ActorCell.invoke(ActorCell.scala:547)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:270)
    at akka.dispatch.Mailbox.run(Mailbox.scala:231)
    at akka.dispatch.Mailbox.exec(Mailbox.scala:243)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)
Caused by: java.lang.ClassNotFoundException: com.mongodb.reactivestreams.client.Success
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
... 24 more

Dependencies:

val akkaHttpVersion = "10.2.1"
val akkaVersion = "2.6.10"
val scalaTestVersion = "3.2.0"
val scalaHtmlScraperVersion = "2.2.0"
val loggerVersion = "1.2.3"
val alpakkaMongoVersion = "2.0.2"

libraryDependencies ++= Seq(
  "org.mongodb.scala" %% "mongo-scala-driver" % "4.1.1",
  "com.typesafe.akka" %% "akka-stream-typed" % akkaVersion,    
  "com.typesafe.akka" %% "akka-http" % akkaHttpVersion,
  "com.typesafe.akka" %% "akka-http-spray-json" % akkaHttpVersion,
  "com.lightbend.akka" %% "akka-stream-alpakka-mongodb" % "2.0.2",
  "ch.qos.logback" % "logback-classic" % loggerVersion,
  "org.scalactic" %% "scalactic" % scalaTestVersion,
  "org.scalatest" %% "scalatest" % scalaTestVersion,
 )

I also tried adding the org.mongodb:mongodb-driver-reactivestreams:4.1.1 dependency, but for some reason com.mongodb.reactivestreams.client.Success isn't part of the binary. I also tried different versions. Some help would definitely be appreciated. I'm using Scala 2.13.3

回答1:

Your problem is related to the Mongo Reactive Streams Driver. The version that Alpakka uses is a little bit old (Aug 13, 2019). See in the Alpakka doc in the "direct dependencies" section:

org.mongodb mongodb-driver-reactivestreams 1.12.0

In that jar you can find the Success class:

来源：https://stackoverflow.com/questions/65513436/mongodb-reactive-streams-run-time-dependency-error-with-alpakka-mongo-connector