hadoop权威指南3.1 实验

JAVA代码

import org.apache.hadoop.fs.FsUrlStreamHandlerFactory;
import org.apache.hadoop.io.IOUtils;
import java.io.InputStream;
import java.net.URL;
public class URLCat {
static {
URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory());
}
public static void main(String[] args) throws Exception {
InputStream in = null;
try {
in = new URL(args[0]).openStream();
IOUtils.copyBytes(in, System.out, 4096, false);
} finally {
IOUtils.closeStream(in);
}
}
}

编译javac  -classpath ../hadoop-core-1.1.2.jar  URLCat.java

必须指定 classpath

运行

hadoop URLCat hdfs://hadoop1:9000/user/hadoop/in/test1.txt

开始一直报错，检查很多次没发现问题，原因就是hdfs后的 ":"写成了"："，即是中文的

[hadoop@hadoop1 myclass]$ hadoop URLCat hdfs：//localhost:9000/user/hadoop/in/test1.txt
Exception in thread "main" java.net.MalformedURLException: no protocol: hdfs：//localhost:9000/user/hadoop/in/test1.txt
        at java.net.URL.(URL.java:586)
        at java.net.URL.(URL.java:483)
        at java.net.URL.(URL.java:432)
        at URLCat.main(URLCat.java:12)