save 方法总是返回类型 unit ，因为这个always else块将在if else语句中执行。
尝试使用if-else语句，而不是if-else语句 Try , Success & Failure . 在 Success 调用下一个函数& Failure 抛出错误或异常。更多信息请查看下面的代码。

Try { 
  df.write.format("orc").option("database","dbname").option("table","tablename").mode("append").save() 
} match {
 case Success(_) => // do your next steps.
 case Failure(ex) => // println ex.
}

失败

scala> df.show(false)
+--------+---+
|name    |age|
+--------+---+
|Srinivas|20 |
+--------+---+

scala> :paste
// Entering paste mode (ctrl-D to finish)

import scala.util._

Try {
  df.write.format("orc").option("database","dbname").option("table","tablename").mode("append").save() // I am not passing path to save method, It should throw an exception & will be catched inside Failure(ex)
} match {
 case Success(_) => // do your next steps.
 case Failure(ex) => {
     println(s"Exception : ${ex}")
 }
}

// Exiting paste mode, now interpreting.
Exception : java.lang.IllegalArgumentException: Expected exactly one path to be specified, but got:

成功

scala> :paste
// Entering paste mode (ctrl-D to finish)

Try {
  df.write.format("orc").option("database","dbname").option("table","tablename").mode("append").save("/tmp/sampledf") // I have given path & It should save df & Success(_) should be invoked.
} match {
 case Success(_) => println("Success Block")
 case Failure(ex) => {
     println(s"Exception : ${ex}")
 }
}

// Exiting paste mode, now interpreting.

Success Block

scala>