No such method exception Hadoop <init>

java hadoop mapreduce
London guy picture London guy · Jul 12, 2012 · Viewed 24.5k times · Source

When I am running a Hadoop .jar file from the command prompt, it throws an exception saying no such method StockKey method.

StockKey is my custom class defined for my own type of key.

Here is the exception:

12/07/12 00:18:47 INFO mapred.JobClient: Task Id :   
attempt_201207082224_0007_m_000000_1, Status : FAILED

java.lang.RuntimeException: java.lang.NoSuchMethodException: SecondarySort$StockKey.      
<init>()
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
    at org.apache.hadoop.io.WritableComparator.newKey(WritableComparator.java:109)
    at org.apache.hadoop.io.WritableComparator.<init>(WritableComparator.java:95)
    at org.apache.hadoop.io.WritableComparator.get(WritableComparator.java:51)
    at org.apache.hadoop.mapred.JobConf.getOutputKeyComparator(JobConf.java:795)
    at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.<init>(MapTask.java:817)
    at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:383)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:325)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:270)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:396)
    at     
   org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1127)
    at org.apache.hadoop.mapred.Child.main(Child.java:264)

Answer

Chris picture Chris · Aug 13, 2013

There's another thing to check when getting errors like this for classes which are writables, mappers, reducers, etc.

If the class is an inner class, make sure it's declared static (i.e. doesn't need an instance of the enclosing class). Otherwise, Hadoop cannot instantiate your inner class and will give this same error - that a zero-arg constructor is needed.

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