问题描述
- 我在java上运行Hadoop的例程 FindFileOnHDFS 结果报错了
-
Exception in thread "main" java.lang.ClassCastException: org.apache.hadoop.fs.LocalFileSystem cannot be cast to org.apache.hadoop.hdfs.DistributedFileSystem
at org.apache.hadoop.examples.FindFileOnHDFS.getHDFSNodes(FindFileOnHDFS.java:43)
at org.apache.hadoop.examples.FindFileOnHDFS.main(FindFileOnHDFS.java:16)
怎么办？
例程的代码如下（代码是肯定没错的）：
package org.apache.hadoop.examples;import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BlockLocation;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.DistributedFileSystem;
import org.apache.hadoop.hdfs.protocol.DatanodeInfo;public class FindFileOnHDFS {
public static void main(String[] args) throws Exception{
getHDFSNodes();
getFileLocal();
}public static void getFileLocal() throws Exception {
Configuration conf = new Configuration();
FileSystem hdfs = FileSystem.get(conf);
Path fpath = new Path("/user/root/20120722/word.txt");FileStatus fileStatus = hdfs.getFileStatus(fpath);
BlockLocation[] blkLocations = hdfs.getFileBlockLocations(fileStatus, 0, fileStatus.getLen());int blockLen = blkLocations.length;
for(int i = 0 ; i < blockLen ; ++i ){
String[] hosts = blkLocations[i].getHosts();
System.out.println("block_"+i + "_location:" + hosts[i]);
}
}public static void getHDFSNodes() throws Exception{
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
DistributedFileSystem hdfs = (DistributedFileSystem)fs;
DatanodeInfo[] dataNodeStats = hdfs.getDataNodeStats();for( int i = 0 ; i < dataNodeStats.length ; ++i ){
System.out.println("DataNode_" + i + "_Node:" + dataNodeStats[i].getHostName());
}
}
}