java.lang.NoClassDefFoundError：scala / Predef $ any2stringadd $

Question

我正在使用Akka Distributed Publish订阅Java，遵循文档中的this examples

但每当我运行我的代码时，我都会得到java.lang.NoClassDefFoundError: scala/Predef$any2stringadd$

似乎无法提交scala库，但我可以在依赖项选项卡上看到scala库。我也对Akka依赖项使用相同的版本。

我对pom.xml：

的依赖

<dependencies>
    <dependency>
        <groupId>org.twitter4j</groupId>
        <artifactId>twitter4j-core</artifactId>
        <version>[4.0,)</version>
    </dependency>
    <dependency>
        <groupId>org.twitter4j</groupId>
        <artifactId>twitter4j-stream</artifactId>
        <version>[4.0,)</version>
    </dependency>
    <dependency>
        <groupId>org.apache.kafka</groupId>
        <artifactId>kafka_2.10</artifactId>
        <version>0.8.2.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.zookeeper</groupId>
        <artifactId>zookeeper</artifactId>
        <version>3.4.6</version>
    </dependency>
    <dependency>
        <groupId>org.apache.storm</groupId>
        <artifactId>storm-core</artifactId>
        <version>0.10.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.storm</groupId>
        <artifactId>storm-kafka</artifactId>
        <version>0.10.0</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.6.4</version>
    </dependency>
    <dependency>
        <groupId>com.typesafe.akka</groupId>
        <artifactId>akka-actor_2.11</artifactId>
        <version>2.4.1</version>
    </dependency>
    <dependency>
        <groupId>com.typesafe.akka</groupId>
        <artifactId>akka-cluster-tools_2.11</artifactId>
        <version>2.4.1</version>
    </dependency>
</dependencies>

IntelliJ显示：

这是导致异常的代码：

ActorSystem actorSystem = ActorSystemManager.INSTANCE.getActorSystem();
ActorRef actorSubscriber = actorSystem.actorOf(Props.create(TwitterSubscriber.class));

ActorSystemManager是一个传递演员系统的单例。

public enum ActorSystemManager {
    INSTANCE;

    private final ActorSystem actorSystem;

    private ActorSystemManager() {
        actorSystem = ActorSystem.create("localized_tweets");
    }

    public ActorSystem getActorSystem() {
        return actorSystem;
    }
}

这是完整的堆栈跟踪：

Connected to the target VM, address: '127.0.0.1:51608', transport: 'socket'
Exception in thread "main" java.lang.NoClassDefFoundError: scala/Predef$any2stringadd$
    at akka.actor.RootActorPath.<init>(ActorPath.scala:273)
    at akka.event.Logging$StandardOutLogger.<init>(Logging.scala:800)
    at akka.event.Logging$.<init>(Logging.scala:821)
    at akka.event.Logging$.<clinit>(Logging.scala)
    at akka.event.LoggingBus$class.setUpStdoutLogger(Logging.scala:74)
    at akka.event.LoggingBus$class.startStdoutLogger(Logging.scala:90)
    at akka.event.EventStream.startStdoutLogger(EventStream.scala:28)
    at akka.actor.ActorSystemImpl.<init>(ActorSystem.scala:613)
    at akka.actor.ActorSystem$.apply(ActorSystem.scala:143)
    at akka.actor.ActorSystem$.apply(ActorSystem.scala:110)
    at akka.actor.ActorSystem$.create(ActorSystem.scala:58)
    at akka.actor.ActorSystem.create(ActorSystem.scala)
    at com.dazito.twitter.akka.ActorSystemManager.<init>(ActorSystemManager.java:16)
    at com.dazito.twitter.akka.ActorSystemManager.<clinit>(ActorSystemManager.java:11)
    at com.dazito.twitter.Main.main(Main.java:36)
Caused by: java.lang.ClassNotFoundException: scala.Predef$any2stringadd$
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 15 more
Disconnected from the target VM, address: '127.0.0.1:51608', transport: 'socket'

有关如何解决此异常的任何帮助？

Answer 1

将您的scala库更新为2.11版本。

Answer 2

您有相互冲突的依赖项：kafka_2.10需要Scala 2.10，而akka-actor_2.11需要Scala 2.11，并且这些库不是二进制兼容的。请改用kafka_2.11。 （虽然你已经接受了另一个答案，如果你不改变Kafka的依赖性，你可能会遇到更多类似的问题。）

Maven无法帮助您，因为它不了解库的Scala版本后缀约定，也不会特别处理scala-library。所以它无法注意到冲突。如果您有Scala依赖项，您可能希望将SBT用于Java项目;或使用

<properties><scala.version>2.11</scala.version></properties>
...
kafka_${scala.version}
...
akka-actor_${scala.version}