獲取 java.lang.NullPointerException hadoop map-reduce 程序

Question

從數據庫中獲取數據並加載到另一個表中時出現以下錯誤：

15/07/01 04:23:15 INFO mapreduce.Job: Task Id : attempt_1434100146148_0014_m_000000_0, Status : FAILED
Error: java.lang.NullPointerException
    at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.initialize(MapTask.java:525)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:763)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340)
    at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:167)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1557)
    at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:162)

Answer 1

謝謝蘇巴

上面的問題得到了解決。我的輸入 sql 查詢中的列名有錯誤。我的查詢是

select * from allTypes where **key** = ?;(correct) 
select * from allTypes where **id** = ?;(wrong ...no column as id)