Apache Flink WordCount 示例 - 线程“main”中的异常 java.lang.NoClassDefFoundError: org/apache/flink/api/common/functions/FlatMapFunction

Question

我关注了this guide，但如果我从我的 IDE 运行 WordCount，我会得到一个异常

/usr/lib/jvm/java-8-oracle/bin/java -Didea.launcher.port=7536 -Didea.launcher.bin.path=/home/marc/Programs/idea-IC-162.2032.8/bin -Dfile.encoding=UTF-8 -classpath "/usr/lib/jvm/java-8-oracle/jre/lib/charsets.jar:/usr/lib/jvm/java-8-oracle/jre/lib/deploy.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/cldrdata.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/dnsns.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/jaccess.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/jfxrt.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/localedata.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/nashorn.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunec.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunpkcs11.jar:/usr/lib/jvm/java-8-oracle/jre/lib/ext/zipfs.jar:/usr/lib/jvm/java-8-oracle/jre/lib/javaws.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jce.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jfr.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jfxswt.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jsse.jar:/usr/lib/jvm/java-8-oracle/jre/lib/management-agent.jar:/usr/lib/jvm/java-8-oracle/jre/lib/plugin.jar:/usr/lib/jvm/java-8-oracle/jre/lib/resources.jar:/usr/lib/jvm/java-8-oracle/jre/lib/rt.jar:/home/marc/apache flink/flink.gelly/target/classes:/home/marc/Programs/idea-IC-162.2032.8/lib/idea_rt.jar" com.intellij.rt.execution.application.AppMain haw.bachelor.flink.gelly.WordCount
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/flink/api/common/functions/FlatMapFunction
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:123)
Caused by: java.lang.ClassNotFoundException: org.apache.flink.api.common.functions.FlatMapFunction
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)
... 3 more

我的环境：

• Ubuntu 14.04 LTS
• Oracle Java 8
• Maven 3.0.5
• intellij 社区版

Answer 1

这是我更改设置的内容，错误消失了

Answer 2

在 Intellij IDEA (2020.3) 中，UI 略有不同。

步骤：

1. 激活运行配置下拉菜单
2. 点击Edit Configurations...
3. 点击Modify Options
4. 选择include dependencies with "Provided" scope
5. 点击“完成”

现在应该包含 Flink 源，这应该可以解决遇到的错误 - 它对我有用！

Answer 3

如果您在 IDE 中运行它，则必须从“运行配置”菜单中选择“mainRunner”而不是“root”。它使类路径加载项目中“提供”的类。

Answer 4

我通过在 IDE 中停用 Maven 中的“build-jar”配置文件解决了这个问题。似乎关闭它将使运行时类可用。