找不到类型为org.apache.spark.sql.Encoder [String]的证据参数的隐式值

Question

我正在尝试将数据框加载到Hive表中。

import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.SaveMode
import org.apache.spark.sql._

object SparkToHive {
  def main(args: Array[String]) {
    val warehouseLocation = "file:${system:user.dir}/spark-warehouse"
    val sparkSession = SparkSession.builder.master("local[2]").appName("Saving data into HiveTable using Spark")
                        .enableHiveSupport()
                        .config("hive.exec.dynamic.partition", "true")
                        .config("hive.exec.dynamic.partition.mode", "nonstrict")
                        .config("hive.metastore.warehouse.dir", "/user/hive/warehouse")
                         .config("spark.sql.warehouse.dir", warehouseLocation)
                        .getOrCreate()
    **import sparkSession.implicits._**
    val partfile = sparkSession.read.text("partfile").as[String]

    val partdata = partfile.map(part => part.split(","))
    case class Partclass(id:Int, name:String, salary:Int, dept:String, location:String)
    val partRDD  = partdata.map(line => PartClass(line(0).toInt, line(1), line(2).toInt, line(3), line(4)))
    val partDF   = partRDD.toDF()
    partDF.write.mode(SaveMode.Append).insertInto("parttab")
  }
}

我还没有执行它，但是在此行出现以下错误：

import sparkSession.implicits._
could not find implicit value for evidence parameter of type org.apache.spark.sql.Encoder[String]

我怎样才能解决这个问题 ？

Answer 1

请把物体移到case class Partclass外面SparkToHive。那应该没事

并且**在您的implicits import声明中。尝试

import sparkSession.sqlContext.implicits._