【问题标题】:Why do I get java.lang.NoClassDefFoundError when I trying to run this code?当我尝试运行此代码时,为什么会出现 java.lang.NoClassDefFoundError?
【发布时间】:2013-01-03 06:40:59
【问题描述】:

我想映射字符串中的字符,但出现运行时错误。

例子:

object Hello {
    def hello(c: Char) {
        print(c)
    }

    def main(args: Array[String]) {
        "Hello World!".map(hello)
    }
}

追踪:

scalac Hello.scala
java Hello
Exception in thread "main" java.lang.NoClassDefFoundError: scala/LowPriorityImplicits
    at Hello.main(Hello.scala)
Caused by: java.lang.ClassNotFoundException: scala.LowPriorityImplicits
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    ... 1 more
make: *** [test] Error 1

【问题讨论】:

  • 它与映射无关,您的类路径有问题。如果您使用java 命令运行您的代码,请将 scala-library.jar 添加到 cp —— java 对 scala 和它的位一无所知。或者使用scala 命令运行代码。
  • scala Hello而不是java Hello运行你的程序。

标签: scala classnotfoundexception


【解决方案1】:

我认为您的问题是 scala 库不在您的运行时类路径中。您必须手动添加。

如果您使用的是 maven 或 sbt 之类的工具,则可能会将依赖项标记为已提供而不是已编译。

如果您不使用这些工具,请将“scala-library.jar”添加到您的库目录中

【讨论】:

    【解决方案2】:

    也看到了这个问题,因为我没有正确版本的 Scala。对于使用 IntelliJ 的用户,您可以在 File > Project Structures > Global Libraries 下添加/更改 scala SDK:

    如果您在命令行中编译和运行项目,请确保您也安装了正确版本的 Scala。例如:

    检查安装的Scala版本:

    $ scala -version
    Scala code runner version 2.11.8 -- Copyright 2002-2016, LAMP/EPFL
    

    检查 build.sbt 以获得正确版本的 Scala:

    scalaVersion := "2.11.8"
    

    【讨论】:

      【解决方案3】:

      我可以确认修复是验证依赖项。或者更确切地说是我的测试库中包含的内容。

      对我来说,我升级了 SpringBoot 版本,这改变了我的 spring-kafka-test 版本,其中实习生包括 kafka 2.13.x,最终包括 scala 库。

      我在项目的构建文件中使用了mvn dependency:tree,并搜索了“2.12”以查找旧依赖项的来源。示例依赖树(删除了不相关的依赖)。注意 org.apache.kafka:kafka_2.11:jar:0.10.0.0 包含在 my.company.riptide.api:ness-logger:jar:1.0.0 中,但 org.springframework.kafka:spring-kafka-test:jar:2.7.9 包含更新版本 org.apache.kafka:kafka_2.13:jar:2.7.2

      我的解决方案是从我的 ness-logger 依赖项中排除 kafaka_2.11,如下所示:

      <dependency>
        <groupId>my.company.riptide.api</groupId>
        <artifactId>ness-logger</artifactId>
        <version>1.0.0</version>
        <exclusions>
          <exclusion>
            <groupId>org.apache.kafka</groupId>
            <artifactId>kafka_2.11</artifactId>
          </exclusion>
        </exclusions>
      </dependency>
      

      mvn dependency:tree 的截断输出:

      [INFO] +- my.company.riptide.api:ness-logger:jar:1.0.0:compile
      [INFO] |  +- org.springframework.boot:spring-boot-starter-validation:jar:2.5.7:compile
      [INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-el:jar:9.0.55:compile
      [INFO] |  |  \- org.hibernate.validator:hibernate-validator:jar:6.2.0.Final:compile
      [INFO] |  |     \- jakarta.validation:jakarta.validation-api:jar:2.0.2:compile
      [INFO] |  +- commons-io:commons-io:jar:2.7:compile
      [INFO] |  +- my.company.eis:ness-logging-package:jar:4.0.1:compile
      [INFO] |  |  +- org.apache.avro:avro:jar:1.8.2:compile
      [INFO] |  |  |  +- org.codehaus.jackson:jackson-core-asl:jar:1.9.13:compile
      [INFO] |  |  |  +- org.codehaus.jackson:jackson-mapper-asl:jar:1.9.13:compile
      [INFO] |  |  |  +- com.thoughtworks.paranamer:paranamer:jar:2.7:compile
      [INFO] |  |  |  \- org.tukaani:xz:jar:1.5:compile
      [INFO] |  |  +- org.apache.avro:avro-compiler:jar:1.8.2:compile
      [INFO] |  |  |  +- org.apache.velocity:velocity:jar:1.7:compile
      [INFO] |  |  |  \- joda-time:joda-time:jar:2.7:compile
      [INFO] |  |  +- org.apache.kafka:kafka_2.11:jar:0.10.0.0:compile
      [INFO] |  |  |  +- com.101tec:zkclient:jar:0.8:compile
      [INFO] |  |  |  \- org.scala-lang.modules:scala-parser-combinators_2.11:jar:1.0.4:compile
      [INFO] |  |  \- com.netflix.hystrix:hystrix-core:jar:1.5.18:compile
      [INFO] |  |     +- com.netflix.archaius:archaius-core:jar:0.4.1:compile
      [INFO] |  |     \- io.reactivex:rxjava:jar:1.3.8:compile
      [INFO] |  +- org.springframework.boot:spring-boot-loader-tools:jar:2.5.7:compile
      [INFO] |  |  \- org.apache.commons:commons-compress:jar:1.21:compile
      [INFO] |  \- my.company.riptide.springboot:graceful-shutdown:jar:1.0.2:compile
      
      [INFO] +- org.springframework.kafka:spring-kafka:jar:2.7.9:compile
      [INFO] |  +- org.springframework:spring-messaging:jar:5.3.13:compile
      [INFO] |  +- org.springframework:spring-tx:jar:5.3.13:compile
      [INFO] |  +- org.springframework.retry:spring-retry:jar:1.3.1:compile
      [INFO] |  |  \- javax.annotation:javax.annotation-api:jar:1.3.2:compile
      [INFO] |  +- org.apache.kafka:kafka-clients:jar:2.7.2:compile
      [INFO] |  |  +- com.github.luben:zstd-jni:jar:1.4.5-6:compile
      [INFO] |  |  +- org.lz4:lz4-java:jar:1.7.1:compile
      [INFO] |  |  \- org.xerial.snappy:snappy-java:jar:1.1.7.7:compile
      [INFO] |  \- com.google.code.findbugs:jsr305:jar:3.0.2:compile
      [INFO] +- junit:junit:jar:4.13.2:test
      [INFO] |  \- org.hamcrest:hamcrest-core:jar:2.2:compile
      [INFO] +- io.cucumber:cucumber-spring:jar:7.0.0:test
      [INFO] |  \- org.apiguardian:apiguardian-api:jar:1.1.2:test
      [INFO] +- io.cucumber:cucumber-core:jar:7.0.0:test
      [INFO] |  +- io.cucumber:cucumber-gherkin:jar:7.0.0:test
      [INFO] |  +- io.cucumber:cucumber-gherkin-messages:jar:7.0.0:test
      [INFO] |  +- io.cucumber:messages:jar:17.1.1:test
      [INFO] |  +- io.cucumber:tag-expressions:jar:4.0.2:test
      [INFO] |  +- io.cucumber:cucumber-expressions:jar:13.0.1:test
      [INFO] |  +- io.cucumber:datatable:jar:7.0.0:test
      [INFO] |  +- io.cucumber:cucumber-plugin:jar:7.0.0:test
      [INFO] |  +- io.cucumber:docstring:jar:7.0.0:test
      [INFO] |  +- io.cucumber:html-formatter:jar:17.0.0:test
      [INFO] |  \- io.cucumber:create-meta:jar:6.0.1:test
      
      [INFO] +- org.springframework.kafka:spring-kafka-test:jar:2.7.9:test
      [INFO] |  +- org.apache.kafka:kafka-clients:jar:test:2.7.2:test
      [INFO] |  +- org.apache.kafka:kafka-streams:jar:2.7.2:test
      [INFO] |  |  +- org.apache.kafka:connect-json:jar:2.7.2:test
      [INFO] |  |  |  \- org.apache.kafka:connect-api:jar:2.7.2:test
      [INFO] |  |  \- org.rocksdb:rocksdbjni:jar:5.18.4:test
      [INFO] |  +- org.apache.kafka:kafka-streams-test-utils:jar:2.7.2:test
      [INFO] |  +- org.apache.kafka:kafka_2.13:jar:2.7.2:test
      [INFO] |  |  +- org.apache.kafka:kafka-raft:jar:2.7.2:test
      [INFO] |  |  +- com.fasterxml.jackson.module:jackson-module-scala_2.13:jar:2.12.5:test
      [INFO] |  |  +- com.fasterxml.jackson.dataformat:jackson-dataformat-csv:jar:2.12.5:test
      [INFO] |  |  +- net.sf.jopt-simple:jopt-simple:jar:5.0.4:compile
      [INFO] |  |  +- com.yammer.metrics:metrics-core:jar:2.2.0:compile
      [INFO] |  |  +- org.scala-lang.modules:scala-collection-compat_2.13:jar:2.2.0:test
      [INFO] |  |  +- org.scala-lang.modules:scala-java8-compat_2.13:jar:0.9.1:test
      [INFO] |  |  +- org.scala-lang:scala-library:jar:2.13.3:compile
      [INFO] |  |  +- org.scala-lang:scala-reflect:jar:2.13.3:test
      [INFO] |  |  +- com.typesafe.scala-logging:scala-logging_2.13:jar:3.9.2:test
      [INFO] |  |  +- org.apache.zookeeper:zookeeper:jar:3.5.9:compile
      [INFO] |  |  |  +- org.apache.zookeeper:zookeeper-jute:jar:3.5.9:compile
      [INFO] |  |  |  +- org.apache.yetus:audience-annotations:jar:0.5.0:compile
      [INFO] |  |  |  \- io.netty:netty-transport-native-epoll:jar:4.1.70.Final:compile
      [INFO] |  |  \- commons-cli:commons-cli:jar:1.4:test
      [INFO] |  +- org.apache.kafka:kafka_2.13:jar:test:2.7.2:test
      [INFO] |  \- org.junit.jupiter:junit-jupiter-api:jar:5.7.2:test
      [INFO] |     +- org.opentest4j:opentest4j:jar:1.2.0:test
      [INFO] |     \- org.junit.platform:junit-platform-commons:jar:1.7.2:test
      

      【讨论】:

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