线程"main" java.lang.NoClassDefFoundError中的异常： org/apache/hadoop/util/Tool

Question

I get below error when i package (jar) and run my defaulthadoopjob. 
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/hadoop/util/Tool
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.util.Tool
    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)
    ... 12 more
Could not find the main class: DefaultHadoopJobDriver. Program will exit.

Commands used to build Jar. 
# jar -cvf dhj.jar 
# hadoop -jar dhj.jar DefaultHadoopJobDriver
The above command gave me error "Failed to load Main-Class manifest attribute from dhj.jar"
rebuilt jar with manifest using below command

jar -cvfe dhj.jar DefaultHadoopJobDriver .
hadoop -jar dhj.jar DefaultHadoopJobDriver -- 这返回了我上面报告的原始错误消息。

我的Hadoop作业具有单个类"DefaultHoopJobDrive"，它扩展了配置和实现工具，并将方法作为作业创建和输入路径，输出路径集的唯一代码运行。Aslo I.m使用新的API。

I'm running hadoop 1.2.1 and the Job works fine from eclipse.
This might be something to do with the classpath. Please help.

Answer 1

要执行该jar，您不必hadoop -jar。命令如下所示：

 hadoop jar <jar> [mainClass] args...

如果这个jar再次出现java.lang.ClassNotFoundException异常，那么你可以使用：

hadoop classpath

命令以查看 Hadoop 安装类路径中是否存在hadoop-core-1.2.1.jar？

仅供参考，如果它不在此列表中，则必须将此jar添加到Hadoop库目录中。

Answer 2

尝试使用 Hadoop

lib 文件夹中提供的所有 Hadoop jar 构建您的 Hadoop Java 代码。在这种情况下，你缺少Hadoop-core-*中存在的hadoop util类.jar

可以在 jar 中构建代码时指定类路径，也可以使用以下命令将其外部化

    hadoop -cp <path_containing_hadoop_jars> -jar <jar_name>

Answer 3

如果有人正在使用 Maven 并降落在这里： 依赖关系问题可以通过要求 Maven 在父项目的 jar 本身中包含它所需的任何 jar 来解决。这样，Hadoop就不必在其他地方寻找依赖关系——它自己就可以在那里找到它们。具体操作方法如下： 1. 去绒球.xml

1. 向<project>标记添加一个名为<build>的部分

2. 将以下内容添加到<build></build>部分：

   <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-shade-plugin</artifactId>
           <version>1.7.1</version>
           <executions>
               <execution>
                   <phase>package</phase>
                   <goals>
                       <goal>shade</goal>
                   </goals>
                   <configuration>
                       <artifactSet>
                           <excludes>
                               <exclude>org.slf4j:slf4j-api</exclude>
                               <exclude>junit:junit</exclude>
                               <exclude>jmock:jmock</exclude>
                               <exclude>xml-apis:xml-apis</exclude>
                               <exclude>org.testng:testng</exclude>
                               <exclude>org.mortbay.jetty:jetty</exclude>
                               <exclude>org.mortbay.jetty:jetty-util</exclude>
                               <exclude>org.mortbay.jetty:servlet-api-2.5</exclude>
                               <exclude>tomcat:jasper-runtime</exclude>
                               <exclude>tomcat:jasper-compiler</exclude>
                               <exclude>org.apache.hadoop:hadoop-core</exclude>
                               <exclude>org.apache.mahout:mahout-math</exclude>
                               <exclude>commons-logging:commons-logging</exclude>
                               <exclude>org.mortbay.jetty:jsp-api-2.1</exclude>
                               <exclude>org.mortbay.jetty:jsp-2.1</exclude>
                               <exclude>org.eclipse.jdt:core</exclude>
                               <exclude>ant:ant</exclude>
                               <exclude>org.apache.hadoop:avro</exclude>
                               <exclude>jline:jline</exclude>
                               <exclude>log4j:log4j</exclude>
                               <exclude>org.yaml:snakeyaml</exclude>
                               <exclude>javax.ws.rs:jsr311-api</exclude>
                               <exclude>org.slf4j:jcl-over-slf4j</exclude>
                               <exclude>javax.servlet:servlet-api</exclude>
                           </excludes>
                       </artifactSet>
                       <filters>
                           <filter>
                               <artifact>*:*</artifact>
                               <excludes>
                                   <exclude>META-INF/jruby.home</exclude>
                                   <exclude>META-INF/license</exclude>
                                   <exclude>META-INF/maven</exclude>
                                   <exclude>META-INF/services</exclude>
                               </excludes>
                           </filter>
                       </filters>
                   </configuration>
               </execution>
           </executions>
       </plugin>
   

现在再次生成项目，并使用普通hadoop java my.jar ...命令运行。它现在不应该为依赖关系哭泣。希望这有帮助！