使用Scala从HDFS读取数据

Question

我是Scala的新手.如何使用Scala从HDFS读取文件(不使用Spark)？当我用谷歌搜索它时,我只找到了HDFS的写入选项.

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

/**
* @author ${user.name}
*/
object App {

//def foo(x : Array[String]) = x.foldLeft("")((a,b) => a + b)

def main(args : Array[String]) {
println( "Trying to write to HDFS..." )
val conf = new Configuration()
//conf.set("fs.defaultFS", "hdfs://quickstart.cloudera:8020")
conf.set("fs.defaultFS", "hdfs://192.168.30.147:8020")
val fs= FileSystem.get(conf)
val output = fs.create(new Path("/tmp/mySample.txt"))
val writer = new PrintWriter(output)
try {
    writer.write("this is a test") 
    writer.write("\n")
}
finally {
    writer.close()
    println("Closed!")
}
println("Done!")
}

}

请帮帮我.如何使用scala从HDFS读取文件或加载文件.

Answer 1

其中一种方式(功能风格)可能是这样的:

val hdfs = FileSystem.get(new URI("hdfs://yourUrl:port/"), new Configuration()) 
val path = new Path("/path/to/file/")
val stream = hdfs.open(path)
def readLines = Stream.cons(stream.readLine, Stream.continually( stream.readLine))

//This example checks line for null and prints every existing line consequentally
readLines.takeWhile(_ != null).foreach(line => println(line))

你也可以看一下这篇文章,或者这里和这里,这些问题看起来与你的相关,并且如果你感兴趣的话,还包含工作(但更像Java的)代码示例.