运行Hadoop权威指南中的例子：3.5.2：FileSystemCat

1、编写代码：

package crt.hadoop.test;

import java.io.InputStream;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;

public class FileSystemCat {
	public static void main(String[] args) throws Exception{
		String uri = args[0];
		Configuration conf = new Configuration();
		FileSystem fs = FileSystem.get(URI.create(uri), conf);
		InputStream in = null;
		try{
			in = fs.open(new Path(uri));
			IOUtils.copyBytes(in, System.out, 4096, false);
		} finally{
			IOUtils.closeStream(in);
		}
	}
}

 

2、把FileSystemCat.java复制到$HADOOP_HOME/build/classes/crt/hadoop/test

 

3、编译：

$ javac  -classpath  $HADOOP_HOME/hadoop-common-0.21.0.jar 

   $HADOOP_HOME/build/classes/crt/hadoop/test/FileSystemCat.java

 

4、运行：

$ export  HADOOP_CLASSPATH=build/classes

$ hadoop  crt.hadoop.test.FileSystemCat  hdfs://hadoop-namenode:9001/tmp/readdatatest.txt

 

运行结果：

hello hadoop