Question

尝试按照说明编译kafka示例流应用

https://github.com/timothyrenner/kafka-streams-ex/tree/master/not-looking-at-facebook

我正在使用 Oracle java8 @ Fedora25

➜  not-looking-at-facebook git:(master) java -version                                                        
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

mvn -X exec：java 会产生以下错误：

java.lang.ClassNotFoundException: io.github.timothyrenner.kstreamex.notification.NotLookingAtFacebook
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:281)
        at java.lang.Thread.run(Thread.java:745)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.517 s
[INFO] Finished at: 2017-03-21T16:17:41-07:00
[INFO] Final Memory: 17M/481M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java (default-cli) on project not-looking-at-facebook: An exception occured while executing the Java class. io.github.timothyrenner.kstreamex.notification.NotLookingAtFacebook -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.4.0:java (default-cli) on project not-looking-at-facebook: An exception occured while executing the Java class. io.github.timothyrenner.kstreamex.notification.NotLookingAtFacebook
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. io.github.timothyrenner.kstreamex.notification.NotLookingAtFacebook
        at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:345)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        ... 20 more
Caused by: java.lang.ClassNotFoundException: io.github.timothyrenner.kstreamex.notification.NotLookingAtFacebook
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:281)
        at java.lang.Thread.run(Thread.java:745)
[ERROR] 
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

我必须使用 mvn clean test 修复它，然后 mvn exec：java 才能使用。出了什么问题？

（我是maven / java生态系统的新手）

Answer 1

您对mvn exec:java的调用失败，因为没有编译任何内容 - 因此缺少主要类。

运行mvn clean test会调用maven-compiler-plugin，这意味着后续尝试使用exec-maven-plugin（在调用exec:java目标时调用的内容）会成功。

如果您查看this question，您会发现将源代码汇编直接绑定到exec:java goal并不是一件么简单。但是，您可以将目标链接在一起，这样的事情可能会起作用：

mvn clean test exec:java

Maven无法使用`mvn exec：java`调用编译java代码（java.lang.ClassNotFoundException）

1 个答案: