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问题描述
当我从命令提示符运行Hadoop .jar文件时,它会抛出一个异常说没有这样的方法StockKey方法。
StockKey是我定制的自定义类
以下是例外情况:
12/07/12 00:18:47信息mapred.JobClient:任务ID: attempt_201207082224_0007_m_000000_1,状态: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)org.apache.hadoop.io.WritableComparator中的。< 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)在org.apache.hadoop.mapred.Child处 $ 4.run(Child.java:270)$ b $在java.security.AccessController.doPrivileged(本地方法)$ b $在javax.security .auth.Subject.doAs(Subject.java:396) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:11 27) at org.apache.hadoop.mapred.Child.main(Child.java:264)解决方案
你必须在你的关键类中提供一个空的默认构造函数。 Hadoop使用反射,它不能猜测任何参数。
因此,只需添加默认构造函数:
public StockKey(){}
When I am running a Hadoop .jar file from the command prompt, it throws an exception saying no such method StockKey method.
StockKey is my custom class defined for my own type of key.
Here is the exception:
12/07/12 00:18:47 INFO mapred.JobClient: Task Id : attempt_201207082224_0007_m_000000_1, Status : FAILED java.lang.RuntimeException: java.lang.NoSuchMethodException: SecondarySort$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)解决方案
You have to provide an empty default constructor in your key class. Hadoop is using reflection and it can not guess any parameters to feed.
So just add the default constructor:
public StockKey(){}
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