15

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)
    }
}

痕迹：

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
4

3 回答 3

8

我认为您的问题是 scala 库不在您的运行时类路径中。您必须手动手动添加。

如果您使用的是 maven 或 sbt 等工具，则依赖项可能被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

于 2016-01-25T11:46:14.863 回答
5

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 ：

在此处输入图像描述

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"
于 2017-05-21T13:52:19.580 回答
0

我可以确认修复是验证依赖项。或者更确切地说，我的测试库中包含的内容。

对我来说，我升级了我的 SpringBoot 版本，它改变了我spring-kafka-test的实习生版本，其中包括 kafka 2.13.x，它最终包括了 scala 库。

我mvn dependency:tree在项目的构建文件中使用并搜索“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）。org.apache.kafka:kafka_2.11:jar:0.10.0.0包含在其中的通知，my.company.riptide.api:ness-logger:jar:1.0.0但org.springframework.kafka:spring-kafka-test:jar:2.7.9包含较新的版本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>

的截断输出mvn dependency:tree：

[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
于 2021-11-29T19:12:41.697 回答