问题
I am trying to run a hadoop job on a server. The version is 0.20.2.
I have a big amount of jars, I am running:
hadoop jar GenData.jar -libjars /path/jar1,path/jar2,...
I am getting the error below even if the corresponding classes are inside the jars:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/avro/mapreduce/AvroKeyInputFormat at GenerateTrainningData.main(GenerateTrainningData.java:256) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.apache.hadoop.util.RunJar.main(RunJar.java:197) Caused by: java.lang.ClassNotFoundException: org.apache.avro.mapreduce.AvroKeyInputFormat at java.net.URLClassLoader$1.run(URLClassLoader.java:366) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
回答1:
Looks like you are getting this exception from Hadoop client side, Mapreduce driver code execution happens in Client JVM. In hadoop -libjars is a generic option which is used for adding dependent jars to mapper/reducer. In your case for adding Jars to Client set you may set the following environment variable,before executing the hadoop command.
export HADOOP_CLASSPATH=<PATH_to_jar>/Jar1:<PATH_to_jar>/Jar2;
(colon ":" can be used for specifying more than 1 jars, In your case you may add the Jar that contains the class org.apache.avro.mapreduce.AvroKeyInputFormat).
New edits
Here first of all you need to find the jar containing the class org.apache.avro.mapreduce.AvroKeyInputFormat. You can find the class inside the jar avro-mapred*.jar (Get the compatible version of avro-mapred-version.jar from internet ) include the same in your classpath using the above command.
回答2:
You are missing avro-mapred dependency.
来源：https://stackoverflow.com/questions/27994644/hadoop-external-jars