把hbase数据导入到hdfs  在运行mapreduce 程序报错！！

报错如下：

Error: java.lang.RuntimeException: java.lang.NoSuchMethodException: com.hadoop3.hbaseapi.day03.Demo02_HbasseToHdfs$ToHdfsMapper.<init>()
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:131)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:722)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:168)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1614)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:163)
Caused by: java.lang.NoSuchMethodException: com.hadoop3.hbaseapi.day03.Demo02_HbasseToHdfs$ToHdfsMapper.<init>()
at java.lang.Class.getConstructor0(Class.java:2892)
at java.lang.Class.getDeclaredConstructor(Class.java:2058)
at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:125)
... 7 more


解决办法：
1.如果自定义writable的时候需要注意，反射过程中需要调用无参构造方法，所以只要在自定义的writable类中加入默认的构造函数即可
2.Map和Reduce类须设置为Static权限修饰！


使用方法2 解决的！