Spark 报错 no Java class corresponding to Product with Serializable found

可能是​​toDF​​之前的数据是这样的：

inputDF.map(row => {
      if (sometimeTrue) {
        (1,2,3)
      } else {
        (1,2)
      }
 }).toDF("1", "2", "3")

结果长度没对齐