【Spark】读取本地文件

最近有一个需求，spark任务读取本地csv文件，拼接成rk之后再去hbase取值进行后续处理。搞了好久都没能解决，记录一下解决思路如下：

1、写入临时文件

spark可以读取本地文件，但打成jar包之后不会自动读取jar包中的文件，需要写入临时文件再进行读取。于是操作如下：

Scala 复制代码

//定义文件路径，从jar包中读取csv文件到inputStream
val inputStream = this.getClass.getResourceAsStream(s"/source/fileName.csv")

//创建临时文件存储csv文件
val tempFile = Files.createTempFile("temp-source",".csv")
val tempFilePath = tempFile.toAbsolutePath.toString

val outputStream = new FileOutputStream(tempFilePath)
val bufferedOutputStream = new BufferedOutputStream(outputStream)

//将inputStream中的数据写入到临时文件
try {
    val buffer = enw Array[Byte](1024)
    var bytesRead = -1
    while ({
        bytesRead = inputStream.read(buffer)
        var bytesRead = -1
    }) {
        bufferedOutputStream.write(buffer,0,bytesRead)
    }
} finally {
    bufferedOutputStream.close()
    outputStream.close()
}
println(s"Temp file created at: ${tempFilePath}")



//读取临时csv文件为DataFrame
val csvDF = spark.read.option("header","true")
            .csv("file:///${tempFilePath}")

2、临时文件上传至HDFS

按照上面的做法发包到集群上运行之后报错。猜测可能因为在集群上运行，driver端读取不到本地创建的临时文件数据。于是将临时文件上传至HDFS，再从hdfs中读取

Scala 复制代码

//将临时文件上传至HDFS
val hdfsPath = new Path("hdfs-source-csv.csv")
FileSystem.get(spark.sparkContext.hadoopConfiguration).copyFromLocalFile(new Path(tempFilePath), hdfsPath)
println(s"File uploaded to HDFS at: ${hdfsPath.toString}")

//读取hdfs文件
val csvDF = spark.read.option("header","true")
            .csv(s"${hdfsPath}")

但是这么做还是失败了。推测是没有写入hdfs的权限。

那只好换个思路：

1、将csv文件转换成sql，写入PG临时表，再从PG读取

2、将csv文件转换成Map，再将Map转换成rdd，进行后续操作

3、摆烂，告诉领导这点工资我做不了，换人做吧

3、读取csv文件传换成Map

复制代码

package scala.test

import org.apache.commons.lang3.StringUtils

import scala.collection.mutable.ArrayBuffer
import scala.util.parsing.combinator._

object CSVParser extends RegexParsers {
  override protected val whiteSpace = """[ \t]""".r

  def field: Parser[String] = quoted | nonQuoted

  def quoted: Parser[String] = "\"" ~> """[^"\n]*""".r <~ "\""

  def nonQuoted: Parser[String] = """[^,\n]*""".r

  def record: Parser[List[String]] = repsep(field, ",")

  def records: Parser[List[List[String]]] = repsep(record, "\n")

  def apply(input: String): ParseResult[List[List[String]]] = parseAll(records, input)
}

// 读csv转成map
object Main {

  def main(args: Array[String]): Unit = {
    val arrayBuffer: ArrayBuffer[List[String]] = new ArrayBuffer[List[String]]()
    val source = scala.io.Source.fromInputStream(this.getClass.getResourceAsStream("/真实停电汇总.csv"))

    source.getLines().foreach(line => {
      val result = CSVParser(line)
      result match {
        case CSVParser.Success(records, _) =>
          records.foreach { record =>
            arrayBuffer.append(record)
          }
        case CSVParser.Failure(msg, _) => println("Parsing failed: " + msg)
        case CSVParser.Error(msg, _) => println("Error: " + msg)
      }
    })

    val head = arrayBuffer.head
    arrayBuffer.tail.foreach(item => {
      if (StringUtils.isNoneEmpty(item.head)) println(head.zip(item).filter(x=>StringUtils.isNotEmpty(x._1)).toMap)
    })

  }
}

4、将Map转换成rdd

方法一：

复制代码

var seq = Seq[Map[String, String]]()
arrayBuffer.tail.foreach(item => {
    //将多个map合并成一个seq
    if(StringUtils.isNoneEmpty(item.head)) seq :+= (head.zip(item).filter(x=> StringUtils.isNotEmpty(x._1)).toMap)
})

val rdd = spark.sparkContext.parallelize(seq).repartition(12)
rdd.map(item => {
    (item("id"), item("name"))
}).toDF("id","name")

方法二：

Scala 复制代码

val head = arrayBuffer.head
val body = arrayBuffer.tail
val rdd = spark.sparkContext.parallelize(body).repartition(12).persist()
rdd.toDF("COL").select(selectCol($"COL", head) :_*)

def selectCol(col: Column, head: List[String]): ArrayBuffer[Column] = {
    val arrayBuffer = new ArrayBuffer[Column]()
    for (i <- head.indices) {
        arrayBuffer.append(col(i).as(head(i)))
    }
    arrayBuffer
}