How to implement Helloworld with HDFS API

The editor will share with you how HDFS API implements Helloworld. I hope you will get something after reading this article. Let's discuss it together.

1. Source code

Import org.apache.hadoop.fs.FsUrlStreamHandlerFactory;import org.apache.hadoop.io.IOUtils;import java.io.InputStream;import java.net.URL;/** * Example 3.1 * / 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);}} package cn.kissoft.hadoop.week04;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IOUtils;import java.io.InputStream;import java.net.URI / * Example 3.2 * / public class Homework1 {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. The operation of .class

Note: in this example, the URLCat class is in default package. If there is a package, the name of that class should be preceded by a package.

3. How .jar works

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