如何构造可用于在 spark/scala 中映射 JavaRDD[org.apache.spark.sql.Row] 的函数？

Question

val drdd = Seq(("a", 1), ("b", 2), ("a", 3)).toDF("name", "value").toJavaRDD
drdd.map{ (row: Row) => row.get(0) }

看起来我传递的匿名函数是 Row => Any 而它期待 org.apache.spark.api.java.function.Function[org.apache.spark.sql.Row,?]

<console>:35: error: type mismatch;
found   : org.apache.spark.sql.Row => Any
required: org.apache.spark.api.java.function.Function[org.apache.spark.sql.Row,?]
   drdd.map{ (row: Row) => row.get(0) }
                        ^

这些函数类型之间有什么区别，我应该如何构造它？谢谢！

Answer 1

例子：

drdd.map(new org.apache.spark.api.java.function.Function[Row, String]() {
    override def call(row: Row): String = row.getString(0)
})