Error:(33, 64) Unable to find encoder for type stored in a Dataset. Primitive types (Int, String, etc) and Product types (case classes) are supported by importing spark.implicits._ Support for serializing other types will be added in future releases.
val values = sources.selectExpr("cast(value as string)").as[String]
import spark.implicits._//注意要放在全局的位置，尤其是方法调用 process_data(values)此方法内部使用到df.map方法，如果在main方法里引入上面的一句，则还是会报错！
val values = sources.selectExpr("cast(value as string)").as[String]