Question

我正在编写我的第一个Hadoop应用程序而且我收到了一个错误。我不太明白这个堆栈跟踪中的一些detials是什么意思。这是一个ClassNotFoundException。我正在Ubuntu Linux v12.10，Eclipse 3.8.0，Java 1.6.0_24上构建它。我通过从Apache站点下载并使用Ant构建Hadoop来安装Hadoop。

当我创建一份工作时，我的崩溃就在程序的第一行。

public static void main(String[] args) throws IOException, InterruptedException,  ClassNotFoundException {

    Job job = new Job(); <<== crashing here.


Program [Java Application]  
com.sandbox.hadoop.Program at localhost:33878   
    Thread [main] (Suspended (exception ClassNotFoundException))    
        owns: Launcher$AppClassLoader  (id=29)  
        owns: Class<T> (org.apache.hadoop.security.UserGroupInformation) (id=25)    
        URLClassLoader$1.run() line: 217    
        AccessController.doPrivileged(PrivilegedExceptionAction<T>, AccessControlContext) line: not available [native method]   
        Launcher$AppClassLoader(URLClassLoader).findClass(String) line: 205 
        Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: 321   
        Launcher$AppClassLoader.loadClass(String, boolean) line: 294    
        Launcher$AppClassLoader(ClassLoader).loadClass(String) line: 266    
        DefaultMetricsSystem.<init>() line: 37  
        DefaultMetricsSystem.<clinit>() line: 34    
        UgiInstrumentation.create(Configuration) line: 51   
        UserGroupInformation.initialize(Configuration) line: 216    
        UserGroupInformation.ensureInitialized() line: 184  
        UserGroupInformation.isSecurityEnabled() line: 236  
        KerberosName.<clinit>() line: 79    
        UserGroupInformation.initialize(Configuration) line: 209    
        UserGroupInformation.ensureInitialized() line: 184  
        UserGroupInformation.isSecurityEnabled() line: 236  
        UserGroupInformation.getLoginUser() line: 477   
        UserGroupInformation.getCurrentUser() line: 463 
        Job(JobContext).<init>(Configuration, JobID) line: 80   
        Job.<init>(Configuration) line: 50  
        Job.<init>() line: 46   
        Program.main(String[]) line: 17 
/usr/lib/jvm/java-6-openjdk-amd64/bin/java (Jan 14, 2013 2:42:36 PM)

控制台输出：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/configuration/Configuration
at org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.<init>(DefaultMetricsSystem.java:37)
at org.apache.hadoop.metrics2.lib.DefaultMetricsSystem.<clinit>(DefaultMetricsSystem.java:34)
at org.apache.hadoop.security.UgiInstrumentation.create(UgiInstrumentation.java:51)
at org.apache.hadoop.security.UserGroupInformation.initialize(UserGroupInformation.java:216)
at org.apache.hadoop.security.UserGroupInformation.ensureInitialized(UserGroupInformation.java:184)
at org.apache.hadoop.security.UserGroupInformation.isSecurityEnabled(UserGroupInformation.java:236)
at org.apache.hadoop.security.KerberosName.<clinit>(KerberosName.java:79)
at org.apache.hadoop.security.UserGroupInformation.initialize(UserGroupInformation.java:209)
at org.apache.hadoop.security.UserGroupInformation.ensureInitialized(UserGroupInformation.java:184)
at org.apache.hadoop.security.UserGroupInformation.isSecurityEnabled(UserGroupInformation.java:236)
at org.apache.hadoop.security.UserGroupInformation.getLoginUser(UserGroupInformation.java:477)
at org.apache.hadoop.security.UserGroupInformation.getCurrentUser(UserGroupInformation.java:463)
at org.apache.hadoop.mapreduce.JobContext.<init>(JobContext.java:80)
at org.apache.hadoop.mapreduce.Job.<init>(Job.java:50)
at org.apache.hadoop.mapreduce.Job.<init>(Job.java:46)
at com.sandbox.hadoop.Program.main(Program.java:18)

Caused by: java.lang.ClassNotFoundException: org.apache.commons.configuration.Configuration
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
... 16 more

Answer 1

您应该添加/usr/lib/hadoop-0.xx/lib中找到的所有jar，以避免出现此类路径问题。

为了给你一个想法，你可以输入hadoop classpath，它会打印出获取Hadoop jar和所需库所需的类路径。

在你的情况下，你错过了hadoop-common-0.xx.jar，所以你应该把它添加到类路径中，你应该好好去。

Answer 2

您的主程序需要org.apache.commons.configuration.Configuration还是org.apache.hadoop.conf.Configuration？

看起来Eclipse已经自动导入了错误的Configuration类，当您的群集上运行hadoop时，该类不在类路径上。

您可以分享您的源代码，尤其是com.sandbox.hadoop.Program类，main方法吗？

Answer 3

我遇到了同样的问题。我通过将commons-configuration-x.x.jar添加到我的构建路径来解决它。它位于$ HADOOP_HOME / lib下。

Hadoop ClassNotFoundException

3 个答案: