How to read data from Hadoop URL
This article focuses on "how to read data from Hadoop URL". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor learn "how to read data from Hadoop URL".
1, write code
Import java.io.*
Import java.net.URL
Import org.apache.hadoop.fs.FsUrlStreamHandlerFactory
Import org.apache.hadoop.io.IOUtils
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)
}
}
}
2, compile the Java code
$Hadoopcom.sun.tools.javac.Mian-d classes URLCat.java
/ / then the class files will be generated in the directory of classes
3, package it into a jar package
Jar cf URLCat.jar classes/URLCat.class
/ / then we will get the URLCat.jar, the source is from classes/URLCat.class
4, run the jar package
Hadoop jar URLCat.jar URLCat hdfs://10.10.12.171/input/WordCount/file1
Result:
Hadoop ok
Hadoop fail
Hadoop 2.3
It can be seen that the contents of hdfs://10.10.12.171/input/WordCount/file1 are output to standard output.
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