classnotfoundexception在运行jar时，尽管它包含所有这些类

kxxlusnw 于 2021-06-02 发布在 Hadoop

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我创造了一个 jar 使用 eclipse 对于 mapreduce 工作。如果你提取 jar 你可以看到在场的所有同学。当你 run 这个 jar 在 hadoop``using hadoop命令它显示如下所示的错误。它不能只识别一个类，即Test_project$TwoDArrayWritables.Test_project是main类和TwoDArrayWritables是一个class内Test_project.TwoDArrayWritables继承TwoDArrayWritable内置类hadoop` .
jar提取图像：

错误：

16/04/05 15:48:28 INFO mapred.JobClient: Task Id : attempt_201604051120_0002_m_000000_1, Status : FAILED
java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:889)
    at org.apache.hadoop.mapred.JobConf.getMapOutputValueClass(JobConf.java:747)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:966)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:422)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:366)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:422)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
    at org.apache.hadoop.mapred.Child.main(Child.java:249)
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:857)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:881)
    ... 9 more
Caused by: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:810)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:855)
    ... 10 more
16/04/05 15:48:34 INFO mapred.JobClient: Task Id : attempt_201604051120_0002_m_000000_2, Status : FAILED
java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:889)
    at org.apache.hadoop.mapred.JobConf.getMapOutputValueClass(JobConf.java:747)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:966)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:422)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:366)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:422)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
    at org.apache.hadoop.mapred.Child.main(Child.java:249)
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:857)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:881)
    ... 9 more
Caused by: java.lang.ClassNotFoundException: mapreduce.Test_project$TwoDArrayWritables
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at org.apache.hadoop.conf.Configuration.getClassByName(Configuration.java:810)
    at org.apache.hadoop.conf.Configuration.getClass(Configuration.java:855)
    ... 10 more

谷歌搜索了许多解决方案，但都没有奏效。请帮帮我！

Java hadoop mapreduce eclipse Jar

来源：https://stackoverflow.com/questions/36446377/classnotfoundexception-while-running-a-jar-though-it-contails-all-tha-classes

2条答案

按热度按时间

w8rqjzmb1#

试试这个： bin/hadoop jar /path/to/jarfile/newproj.jar Test_project.TwoDArrayWritables /user/hduser/input /user/hduser/output1

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2sbarzqh2#

挣扎了大约几个星期后，我的脑海中突然出现了一些东西，即我在工作中使用了两个减速机，因此为每个减速机定义了两个jobconf：
我以前的（错误代码） JobConf conf = new JobConf(getConf(), Test_project.class); JobConf conf2 = new JobConf(getConf()); 因为我认为配置已经定义好了，所以在conf2中没有提到类test\u project.class****
我的礼物（正确代码） JobConf conf = new JobConf(getConf(), Test_project.class); JobConf conf2 = new JobConf(getConf(), Test_project.class); 引发错误的原因是，在执行时，它正在搜索test\u project$twodarraywritables，因为它没有test\u project.class类，所以找不到twodarraywritables
现在可以了。

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我来回答

classnotfoundexception在运行jar时，尽管它包含所有这些类

2条答案

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