spark报错 java.lang.NullPointerException: Null value appeared in non-nullable field:top level Product

java.lang.NullPointerException: Null value appeared in non-nullable field:
top level Product input object
If the schema is inferred from a Scala tuple/case class, or a Java bean, please try to use scala.Option[_] or other nullable types (e.g. java.lang.Integer instead of int/scala.Int).

package com.test

import org.apache.spark.sql.{Dataset, SparkSession}

import java.lang
import scala.collection.mutable.ListBuffer
import scala.util.control.Breaks.{break, breakable}

object scalaDemo1 {
  def main(args: Array[String]): Unit = {

    val spark = SparkSession.builder()
      .master("local[*]")
      .appName("yy")
      .getOrCreate()
    val sc = spark.sparkContext
    spark.sparkContext.setLogLevel("ERROR")
    // For implicit conversions like converting RDDs to Dataframes
    import spark.implicits._
    import org.apache.spark.sql.functions._ //解决:无法重载方法agg

    // 方法1
    val